Related Terms

• Acquired immunodeficiency syndrome, acute viral nasopharyngitis, AIDS, antibody, antigen, antihistamine, antiviral, asthma, avian flu, bronchial tubes, bronchitis, CHD, chemotherapy, cholesterol, coronary heart disease, cytokine storm, decongestant, dehydration, diabetes, Fahrenheit, fatigue, flu, H1N1, H5N1, heart attack, HIV, human immunodeficiency virus, immunization, infection, influenza, influenza A virus subtype H1N1, influenza-like illness (ILI), larynx, malaise, mucous membrane, mucus, novel H1N1 flu, otitis media, pandemic, pandemic H1N1/09, pigs, pneumonia, respiratory syncytial virus, rhinoviruses, RSV, RT-PCR, sinus, sinusitis, sputum, Spanish flu, stress, subtype, swine, swine flu, swine-origin influenza A (H1N1) virus, trachea, transmission, tuberculosis, vaccination, vaccine, viral infection, virus.

Background

• H1N1 is a subtype of the type A influenza virus that causes an illness commonly known as the flu. There are three types of influenza virus (A, B, and C), and each type may have various subtypes. New strains may develop when the virus mutates. The H1N1 subtype currently holds much interest because an ongoing pandemic involves a novel (new) strain of the virus. This outbreak began in late March of 2009 in Mexico and is predicted to continue into the regular flu season of 2009-10.

• This novel strain was originally referred to as "swine flu" because it appeared similar to influenza viruses that normally infect pigs (swine) and rarely infect humans. There was widespread concern that eating pork or coming into contact with pigs would increase the risks of contracting the novel H1N1 flu. Because people began to avoid pork for fear of catching H1N1, the pork industry suffered. Travel to Mexico was restricted, which also had negative economic effects. In late April 2009, 300,000 pigs were slaughtered in Egypt in an effort to curb the disease, even though no cases of H1N1 had been reported in Egypt at that time.

• Later studies showed that this novel H1N1 strain (henceforth, H1N1 or novel H1N1) is quite distinct from influenza viruses that normally infect pigs. It appears that the virus is derived from multiple viruses that may have originated in swine. Novel H1N1 is spread from humans to humans and is not known to be transmitted by eating pork or from close contact with swine. It has not yet been identified in pigs in the United States, and only isolated herds of swine have been infected around the world. Thus, the term "swine flu" is somewhat of a misnomer. Nonetheless, it is still currently used to refer to novel H1N1.

• According to the U.S. Centers for Disease Control (CDC), as of September 2009, around 9,000 people in the United States have been hospitalized due to novel H1N1 infection, and fewer than 600 deaths are linked to this new virus. It is estimated that a total of one million people have contracted H1N1 flu in the United States. This is far less than the number of cases caused by seasonal flu viruses, which infect an average of 5-20% of the U.S. population (up to 60 million people) each year. Annually, seasonal flu viruses cause around 200,000 severe cases (requiring hospitalization) and 36,000 deaths. However, what makes H1N1 influenza unique is that infections peaked outside of the regular flu season, and it is currently the predominant strain of the influenza virus worldwide.

• Another unique feature of novel H1N1 influenza is that more infections occur in people under age 60. With seasonal flu, the above-60 population is usually considered to be at high risk. However, the elderly seem to be more resistant to novel H1N1 infection, perhaps because previous exposure to similar viruses has increased their immunity to this new strain. However, people with lower immunity are still at increased risk of infection for any strain of flu, as well as serious complications. This includes young children and those with certain health conditions that hinder the immune system, including cancer, human immunodeficiency virus (HIV), and acquired immunodeficiency syndrome (AIDS). Children also easily spread the virus to others due to poor hygiene, such as sneezing without covering the nose.

• As with seasonal influenza viruses, novel H1N1 flu is transmitted through the air in tiny droplets when someone with the infection coughs, sneezes, or talks. Individuals are then exposed to the virus through inhalation, or by contact with objects such as telephones, door handles, railings, or computer keyboards. An infection may occur when the virus is then transferred to the eyes, nose, or mouth.

• The symptoms of novel H1N1 flu are similar to those of seasonal flu. In fact, novel H1N1 has thus far caused milder symptoms than seasonal flu. Treatment for the flu, regardless of strain, includes bed rest and plenty of fluids, along with symptomatic treatment, such as drugs to fight viral infections, reduce fever, and help with sore throat and cough. An annual influenza vaccine may offer protection against some strains of the influenza virus. Other forms of prevention include frequent hand washing, avoiding touching the nose or face, and avoiding contact with infected individuals.

• When a flu epidemic occurs, specific populations are infected with a type of influenza virus that has not been encountered before. Epidemics may be restricted to one locale (an outbreak), or they may be more general (an "epidemic") or even global (a pandemic). Because novel H1N1 influenza is causing infections globally, it is currently classified as a pandemic. However, the rates of infection have been far less than well-known pandemics, such as the 1918 "Spanish flu" pandemic that killed between 50 and 100 million people worldwide. Both the current pandemic and the 1918 pandemic are attributed to the H1N1 subtype. Therefore, global health experts are advising caution for the upcoming flu season.

• In the southern hemisphere, the seasonal flu period is between April and November. By late August of 2009, the levels of influenza (including H1N1) had returned to normal in the southern hemisphere, according to the World Health Organization.

Risk Factors

• Age: Children and the elderly are especially susceptible to the flu. Children's immune systems have not adjusted to as many viruses as adults, and their bodies are still developing resistance to most microorganisms. Children may not be as careful about cleanliness, such as hand washing, and they also tend to spend an increased amount of time with other children, making it easy for viruses to be transmitted from person to person. Individuals residing in nursing homes or long-term care facilities are also at high risk of contracting influenza due to increased chances of exposure. However, elderly individuals seem to have a somewhat lower risk for novel H1N1 infection than younger people, perhaps because they were exposed to a similar virus in the past and already have some immunity to it.

• Flu season: Influenza occurs mostly during the winter months. In cold months when the air is very dry, people turn on their heating systems, drying the air even more. This tends to dry out the mucous membranes in the nose and throat, the first line of defense against the viruses, allowing the viruses to attack the tissue in the nose and throat. Flu season in the United States starts in November and continues through April. However, the current H1N1 pandemic is occurring outside of the regular flu season.

• In the southern hemisphere, the seasonal flu period is between April and November. By late August of 2009, the levels of influenza (including H1N1) had returned to normal in the southern hemisphere, according to the World Health Organization.

• Vaccination: An annual flu vaccination may lower the risks of getting a flu infection. Because influenza viruses mutate (change) quickly, new vaccines must be created every year. The flu vaccine is designed to prevent specific strains of flu that are predicted to be the dominant strains for the upcoming flu season. Because H1N1 appeared at the end of the 2008-2009 flu season, the vaccine that was available at the time did not prevent its spread. On September 15, 2009 the U.S. Food and Drug Administration (FDA) announced that it approved four vaccines against the 2009 H1N1 influenza virus, manufactured by CSL Limited, MedImmune LLC, Novartis Vaccines and Diagnostics Limited, and Sanofi pasteur Inc.

• Other risk factors affecting immunity: Stress can lower resistance to infection by depressing the immune system. Stress during premenstrual syndrome (PMS) or menopause may increase the chances of developing the flu. Diets that lack sufficient levels of fat, vitamins, and minerals are associated with decreased immunity. Proper sleep (eight hours of uninterrupted sleep for an adult) may help keep the body's immune system healthy, which may in turn help prevent flu infections. Bad hygiene, such as improper hand washing and frequently touching the nose or mouth, can contribute to influenza infection and transmission.

• Social exposure: Individuals exposed to large numbers of people during the day are also exposed to many viruses including influenza. Children attending school or playing with their peers are at increased risk of influenza infection and transmission. Individuals working for the public and for large businesses with many workers are at an increased risk. Traveling in airplanes or buses, or travel to areas with high rates of infection may also increase the risk of contracting influenza viruses.

• Current health condition: Individuals who are most susceptible to influenza virus infections include those with chronic lung diseases, such as asthma, emphysema (lung disease), chronic (long-term) bronchitis (inflammation of the bronchial tubes), bronchiectasis (chronic opening of bronchial tubes), tuberculosis (TB, an infection of the lungs), and cystic fibrosis (scar tissue formation in the lungs). Heart conditions, such as coronary heart disease (CHD, which includes high blood pressure, high cholesterol, and heart attack), as well as chronic kidney disease, diabetes, severe anemia (a decrease in red blood cells which carry oxygen), and diseases that depress immunity, such as cancer, human immunodeficiency virus (HIV), and acquired immunodeficiency syndrome (AIDS), are also risk factors for contracting the influenza virus. Certain medications, such as some steroids and chemotherapeutic agents, may also lower immune function and can increase susceptibility to developing the flu.

Causes

• Novel H1N1 flu is caused by the H1N1 subtype of the type A influenza virus. Type A influenza viruses tend to cause more serious infections than the two other major types (B and C), because the virus mutates and changes quickly, which results in various subtypes. Type A viruses most commonly affect adults and are the most severe, while type B viruses typically affect children and may also be severe. Unlike types A or B, the type C influenza virus causes either a very mild illness (usually in children) or no symptoms at all. It generally does not cause epidemics and does not have a severe public health impact. Another pandemic flu virus, the avian (bird) flu, is also a type A influenza virus, but it is the H5N1 subtype.

• New viral subtypes can develop when a virus mutates (changes its DNA). Mutations can cause a virus to start infecting other species or types of animals. Novel viruses may also contain genes from several other viral subtypes. For example, the current H1N1 pandemic virus contains genes similar to several influenza viruses that infect pigs, birds, and humans. Novel H1N1 was originally believed to arise from pig farms in Mexico. However, it now seems that the novel H1N1 virus may have originated in Asia in pigs that harbored numerous strains of flu viruses. These viruses may have exchanged genetic information while within infected pigs, thus gaining the ability to infect other animals. It is currently believed that this novel strain was transmitted to humans, who then spread the disease to other humans.

• The novel strain has not yet been identified in pigs in the United States. However, an outbreak of novel H1N1 did occur in a herd of pigs in Alberta, Canada, in May 2009. It was thought at first that a farmer who recently returned from Mexico somehow transmitted the virus to the herd. Some of the pigs became ill, and the herd was destroyed. However, the farmer tested negative for the novel H1N1 strain, and it remains unclear how the herd contracted the virus.

• In June 2009, another outbreak of novel H1N1 affected a herd of pigs in Argentina. About 30% of the pigs fell ill. Two pig farm workers also developed flu-like symptoms but tested negative for the novel H1N1 virus. Novel H1N1 has also been reported in Australian swine, and most recently in turkeys in Chile. The infection of birds with H1N1 is very concerning because the avian flu (H5N1) may co-infect the same birds, which creates an opportunity for the viruses to exchange genetic material and develop new characteristics.

• It is possible that the novel H1N1 virus may be a dominant strain during the 2009-2010 flu season. It may also mutate further and acquire the ability to infect other animals. However, it is difficult to predict how a strain will develop during flu season, and the total impact of this novel virus remains uncertain.

Signs and Symptoms

• Adults: The symptoms of novel H1N1 influenza are somewhat milder than seasonal influenza. All types of flu present with symptoms very similar to the common cold (sneezing, nasal drainage, stuffy nose, sore throat, and low fever). Symptoms usually appear suddenly and may include a fever of 101 degrees Fahrenheit (°F) or above, cough, muscle aches and pains, headache, sore throat, chills and sweats, loss of appetite, fatigue (tiredness), and malaise (general bad feeling). The fever and body aches can last 3-5 days, and the cough and lack of energy may last for two weeks or more.

• Most adults recover from the flu within one or two weeks, but others, especially the elderly and those with compromised immune systems (such as HIV/AIDS or cancer patients) may feel weak and debilitated for several weeks after the infection has gone.

• Children: Flu symptoms in school-age children and adolescents are similar to those in adults. However, children may experience vomiting and diarrhea with the flu, which are rare in adults. Influenza infection in preschool children and infants is difficult to diagnose since its symptoms are so similar to infections caused by other viruses.

Diagnosis

• Influenza is usually diagnosed based on symptoms consistent with influenza-like illness (ILI). These include fever, cough, and sore throat.

• Because novel H1N1 influenza causes symptoms that are similar to those of seasonal flu, it is difficult to diagnose H1N1 flu based on symptoms alone. Viral cultures may be performed, but they are time-consuming and not very accurate, as a negative culture does not necessarily mean that flu is not present.

• The most commonly used tests only identify influenza type (such as A, B, or C) and not a subtype. Identification of influenza subtypes requires more sophisticated molecular techniques, such as real-time reverse-transcription polymerase chain reaction (RT-PCR), which amplifies the genetic material of the virus enough so it can be analyzed. Tests are expensive and time-consuming, so they are generally reserved for special cases.

• Diagnosis of novel H1N1 is made according to the U.S. Centers for Disease Control (CDC) case definitions. A probable case is defined as someone with ILI who tests positive for influenza type A, but negative for subtypes H1 and H3 by RT-PCR. A confirmed case is defined as someone with acute illness and laboratory-confirmed infection with H1N1 by either RT-PCR or viral culture.

Complications

• If an individual is healthy with a properly functioning immune system, influenza usually is not serious. Although the individual may feel tired and sick, the flu usually goes away within a few days to a few weeks with no lasting effects.

• Complications of flu arise when the individual's immune system cannot fight off the viral infection. Complications can include bacterial pneumonia, ear infections, bronchitis (inflammation of the bronchial tubes), sinus infections, dehydration (loss of fluids), and worsening of chronic medical conditions, such as congestive heart failure (CHF), asthma, or diabetes. These complications can be long-term.

• An immune complication known as a "cytokine storm" may occur during infection with H1N1 or any other type of virus. This cytokine storm is a strong reaction of the body's defense mechanisms acting against an infectious agent, and the immune response may actually be responsible for many of the symptoms associated with the flu.

Treatment

• Treatment for novel H1N1 influenza follows the same guidelines as any other type of flu. Healthcare professionals recommend bed rest, adequate liquids, and good nutrition for rapid recovery and to prevent dehydration (fluid loss). Those individuals infected by the influenza virus who are otherwise healthy may not need treatment by a doctor unless symptoms persist for more than a few weeks or are severe.

• There are effective treatments available that can reduce the duration of the symptoms caused by the flu. Over-the-counter (OTC) medications can be purchased without a prescription and may help relieve symptoms associated with the flu, including body aches and pains, stuffy or runny nose, fever, and cough. Many products in pharmacies and other retailers contain these medicines separately or in various combination products. Specific formulations are chosen based upon the patient's symptoms.

• Pain relievers and fever reducers: For fever, sore throat, body aches, and headache, acetaminophen (Tylenol®) or ibuprofen (Advil®, Motrin®) may be purchased over the counter (OTC). Acetaminophen can cause liver damage, especially if taken chronically or in doses that exceed four grams daily. Healthcare professionals recommend carefully following dosing guidelines when giving acetaminophen to children, as dosing can be confusing. Ibuprofen in prolonged and large doses can cause kidney and liver damage. Also, it is recommended to never give aspirin to children until they reach the age of 12. Aspirin may play a role in causing Reye's syndrome, a rare but potentially fatal illness, which most commonly occurs in children taking aspirin for viral illnesses (such as influenza and chicken pox).

• Nasal decongestants: Nasal decongestants are useful medications for nasal symptoms associated with the flu, such as "stuffy" nasal passages. Nasal decongestants help dilate (open) swollen mucous membranes of the nasal passages so the individual can breathe easier. Nasal decongestants are available in various formulations, including tablets, sprays, inhalers, and nose drops. Nasal decongestants include the oral decongestant pseudoephedrine (Sudafed®), nasal sprays oxymetolazone (Afrin®) and phenylephrine (Neo-Synephrine®), and the nasal inhalers propylhexedrine (Benzedrex®) or levmetamfetamine (Vicks Vapor Inhaler®). They are safe for most patients, but they should not be used in patients with heart disease, high blood pressure, thyroid disease, glaucoma (increased pressure in the eyes), diabetes, seizure disorders, enlarged prostate, or by individuals using a monoamine oxidase inhibitor (a rarely prescribed antidepressant). Common side effects include stinging, burning, sneezing, increased nasal discharge, drying of the nostrils, loss of smell sensation, and altered taste. Other side effects include rapid or pounding heartbeat, dizziness, trouble sleeping, shaking of the hands, and tremors. If these adverse effects continue beyond two weeks or become very severe, professional medical attention should be sought. Healthcare professionals recommend not using decongestants while pregnant or breastfeeding.

• If used for longer than three days, decongestants (nose drops, inhalers, or sprays) may actually cause rebound congestion, which means the nasal passages are not able to function normally without using these medications. Decongestant overuse may also cause chronic inflammation of the mucous membranes.

• There is widespread national abuse of pseudoephedrine to make methamphetamine (crystal meth or meth), an illegal drug. Methamphetamine is a highly addictive, synthetically produced central nervous system stimulant with effects similar to cocaine. Meth is the most prevalent synthetic drug manufactured in the United States and is easily produced in home laboratories using common store-bought chemicals. The ease of manufacturing meth and its highly addictive potential has caused the use of the drug to increase throughout the nation. Its use has reached epidemic levels in many parts of the country. National and state laws have attempted to stem this criminal activity by establishing limits on sales of pseudoephedrine. The pharmacist or pharmacy representative is required by law to ask for photo identification to ensure that the pseudoephedrine is purchased legitimately as a decongestant. There may also be limits on the how much pseudoephedrine can be purchased in one transaction as well as over a certain time period. In most states, pseudoephedrine products are only available for purchase from behind a counter. In some states, such as Oregon, products containing pseudoephedrine may require a prescription. Also, a new oral nasal decongestant formulation (Sudafed PE®) that decreases the potential for abuse is now available. Sudafed PE® contains the nasal decongestant phenylephrine and not pseudoephedrine.

• Antihistamines: Antihistamines dry up excess nasal secretions (mucus) and in this way help to temporarily stop a runny nose. But they can also cause side effects such as dry mouth, constipation, and drowsiness as well as confusion and increased risk of falls if administered to elderly patients. Non-sedating antihistamines include fexofenadine (Allegra®) and cetirizine (Zyrtec®). Antihistamines that cause sedation include diphenhydramine (Benadryl®), clemastine (Tavist®), chlorpheniramine (Chlor-Trimeton®), and brompheniramine (Dimetane®).

• Cough syrups: Nonprescription cough syrups, containing various combinations of antihistamines, decongestants, and cough suppressants, are available over the counter (OTC) for symptomatic relief of cough associated with the flu. Many doctors strongly discourage the use of these combination medications for any child younger than age two, in whom accidental overdoses could be fatal. Coughs associated with the flu usually last less than 2-3 weeks. If a cough lasts longer than three weeks, a doctor should be seen. If the cough is productive (brings up mucus), the ingredient guaifenesin can help break up the chest congestion. If the cough is dry and hacking, a cough suppressant (dextromethorphan) can stop the cough.

• Lozenges: Sore throat caused by the flu may be self-treated if the pain is minor. Healthcare professionals recommend not self-treating sore throat for more than two days. Lozenges for sore throat contain active ingredients such as the anesthetics benzocaine, menthol, dyclonine, phenol/sodium phenolate, and hexylresorcinol. Phenol/sodium phenolate and hexylresorcinol also have antibacterial properties.

• Antiviral drugs: Certain antiviral medications, such as amantadine (Symmetrel®), rimantadine (Flumadine®), zanamavir (Relenza®), and oseltamivir (Tamiflu®) have been approved by the U.S. Food and Drug Administration (FDA) for the treatment and prevention of influenza. These antivirals are available by prescription only and are reportedly 70-90% effective in preventing influenza in healthy adults. However, these medications are not recommended for prophylactic (preventive) use in the general public due to the potential for influenza viral strains to mutate and become resistant to the drugs. Preventive antiviral use is generally reserved for healthcare workers.

• All of the antiviral medications approved for treating influenza appear to be effective for influenza A viruses. However, only zanamavir (Relenza®) and oseltamivir (Tamiflu®) are effective for influenza B viruses. Recent evidence indicates that a high proportion of currently circulating influenza A viruses in the United States have developed resistance to amantadine (Symmetrel®) and rimantadine (Flumadine®). According to the World Health Organization (WHO), nearly 95% of H1N1 viruses tested were already resistant to Tamiflu® by March of 2009.

• In August 2009, the WHO updated its guidelines for treating H1N1 and other forms of influenza with antiviral medications. According to these guidelines, antiviral treatment is generally reserved for severe or progressive flu in at risk patients (including those younger than five years of age, those older than 65 years of age, pregnant women, immunosuppressed patients, and patients with chronic disease). Oseltamivir is the first-line treatment for severe or progressive flu in all patient groups (including pregnant women, infants, and children). If oseltamivir is not available (or if the virus is resistant), then zanamivir is to be given. For patients not at risk with uncomplicated cases of influenza, antiviral treatment is not recommended.

• For preventing H1N1 or other forms of flu, the WHO only recommends antiviral medications post-exposure if there is a high risk of complications and human-to-human disease transmission. If there is a low risk of complications, then antiviral prophylaxis (preventative use) is not recommended, even in healthcare workers or at-risk groups.

• Amantadine should not be used in pregnant women. Furthermore, otherwise healthy patients should not be treated with antivirals. However, if a patient presents with multiple influenza viruses (including H5N1), then combination therapy with antiviral medications should be considered.

• All antiviral medications used to treat or prevent flu must be taken for 3-5 days in a row (five days for oseltamivir and zanamivir). When antiviral medications are used to treat existing flu infections, they are most effective when taken within two days after developing influenza-like symptoms.

• As with many medications, antivirals used for influenza may have side effects. These include lightheadedness, nausea, vomiting, loss of appetite, and trouble breathing. If symptoms of the flu such as fever and aches get worse, individuals should seek medical advice. In November 2006, the FDA required the maker of oseltamivir (Tamiflu®) to include a warning that people with the flu, particularly children, may be at increased risk of self-injury and confusion after taking oseltamivir (Tamiflu®). The FDA recommends that individuals with the flu who take oseltamivir (Tamiflu®) be closely monitored for signs of unusual behavior.

Integrative Therapies

• Note: Currently, there is insufficient evidence available on the safety and effectiveness of integrative therapies for the prevention or treatment of influenza caused by novel H1N1 or other influenza virus strains. The therapies listed below have been studied for related conditions, should be used only under the supervision of a qualified healthcare provider, and should not be used in replacement of other proven therapies or preventive measures.

• Strong scientific evidence:

• Andrographis: Andrographis (Andrographispaniculata) has been widely used in Indian (Hindu) folk medicine and Ayurvedic forms of medicine. Research suggests that andrographis may reduce symptom severity and duration in active respiratory infections if started within 36-48 hours after symptoms develop. Additional studies are needed, especially those that test the effects of andrographis as a monotherapy for upper respiratory tract infection (URI) treatment.

• Caution is advised when taking andrographis, as adverse effects and potential drug interactions are possible. Avoid in patients experiencing infertility or in those actively trying to conceive. Use cautiously in patients with diabetes, bleeding disorders, and high or low blood pressure. Use cautiously with blood sugar-altering medications (such as insulin), warfarin or other blood-thinning medications, and blood pressure-altering medications (such as atenolol). Andrographis should not be used in patients who are pregnant or breastfeeding, unless otherwise directed by a doctor.

• Good scientific evidence:

• Echinacea: Multiple studies have suggested that oral echinacea may reduce the length and severity of URI symptoms. However, the evidence is weak overall, and more recent studies have produced conflicting evidence. Moreover, there is strong evidence that echinacea does not effectively treat URI in children, though it may offer some benefit in URI prevention. Further research is needed regarding the use of echinacea for treatment of URI infections in adults or prevention of URI in adults or children.

• Avoid if allergic to echinacea, its constituents, or any members of the Asteraceae or Compositae family (ragweed, chrysanthemums, marigolds, daisies). Use cautiously in patients prone to atopic reactions and in those with hemochromatosis and diabetes. Avoid using echinacea in patients presenting for anesthesia.

• Some natural medicine experts discourage the use of echinacea by people with conditions affecting the immune system, such as HIV/AIDS, some types of cancer, multiple sclerosis, tuberculosis, and rheumatologic diseases (such as rheumatoid arthritis or lupus). Use parenteral preparations of echinacea(no longer approved for use in Germany) cautiously. Use tinctures cautiously with alcoholic patients or in patients taking disulfiram or metronidazole. Use cautiously in patients who are pregnant or breastfeeding.

• Elderberry: Elderberry juice may improve symptoms of influenza, such as fever, fatigue, headache, sore throat, cough, and aches. Additional research is needed in this area before a firm conclusion can be reached.

• Cyanide toxicity is possible. Elderberries must be cooked to prevent nausea or cyanide toxicity. Avoid if allergic to elder or to plants related to honeysuckle. Some reports exist of allergies from contact with fresh elder stems. Use cautiously in patients with diabetes, high blood pressure, or urinary problems, or those taking drugs used for any of these conditions. Use cautiously in patients taking anti-inflammatory medications, diuretics, or laxatives. Avoid in patients who are pregnant or breastfeeding.

• Unclear or conflicting scientific evidence:

• Alizarin: Limited available evidence suggests that alizarin may be of benefit in the treatment of viral infections. Additional research is needed in this area.

• Avoid if allergic or hypersensitive to alizarin or any plants in the Rubiaceae family. Alizarin may be toxic and should not be handled for long periods of time, rubbed in the eyes, or eaten. Avoid in patients who are pregnant or breastfeeding.

• Andrographis: A combination of andrographis with Siberian ginseng or eleuthero (Eleutherococcus senticosus) called Kan Jang® has been reported effective as part of a regimen in Asian medical systems to treat influenza. Early studies also suggest that andrographis extract may help with upper respiratory tract infection prevention during the winter months if taken daily. Larger studies are required to confirm these results.

• Caution is advised when taking andrographis, as adverse effects including drug interactions are possible. Avoid in patients experiencing infertility or in those actively trying to conceive. Use cautiously in patients with diabetes, bleeding disorders, and high or low blood pressure. Use cautiously with blood sugar-altering medications, warfarin or other blood thinning medications, and blood pressure-altering medications. Andrographis should not be used in patients who are pregnant or breastfeeding, unless otherwise directed by a doctor.

• Arginine: Arginine, or L-arginine, is considered a semi-essential amino acid because although it is normally synthesized in sufficient amounts by the body, supplementation is sometimes required. Early studies suggest that arginine supplements may decrease the risk of respiratory infections. Large, well-controlled studies are needed to clarify this relationship.

• Avoid if allergic to arginine, or if there is a history of stroke, or liver or kidney disease. Avoid in patients who are pregnant or breastfeeding. Use caution with blood-thinning drugs (like warfarin or Coumadin®) and blood pressure drugs or herbs or supplements with similar effects. Blood potassium levels should be monitored. L-arginine may worsen symptoms of sickle cell disease. Caution is advised in patients taking prescription drugs to control blood sugar levels.

• Astragalus: Astragalus (Astragalus membranaceus) is often used in Chinese medicine as a part of herbal mixtures to prevent or treat upper respiratory tract infection. Antiviral activity has been reported in laboratory and animal studies and in limited human reports. However, most studies have been small and poorly designed. Due to a lack of well-designed research, firm conclusions cannot be drawn at this time.

• Caution is advised when taking astragalus supplements, as adverse effects including drug interactions are possible. Astragalus should not be used in patients who are pregnant or breastfeeding, unless otherwise directed by a doctor.

• Blessed thistle: Human research of blessed thistle as a treatment for viral infections is lacking. Additional study is needed in this area.

• Blessed thistle is generally considered to be safe when taken by mouth in recommended doses for short periods of time. Rare side effects have occurred, including birth defects, bleeding, breathing problems, bruising, cancer of the nose or throat, increased production of stomach acid, itching, kidney disease, liver toxicity, skin rash, stomach discomfort, stomach ulcers, and vomiting. Allergic reactions to blessed thistle including rash may occur, as well as cross-sensitivity to mugwort and Echinacea. Cross-reactivity may also occur with bitter weed, blanket flower, Chrysanthemum, coltsfoot, daisy, dandelion, dwarf sunflower, goldenrod, marigold, prairie sage, ragweed, or other plants in the Asteraceae/Compositae family. Avoid in patients who are pregnant or breastfeeding.

• Boneset: Boneset (Eupatorium perfoliatum) is native to eastern North America and was used by Native Americans to treat fevers, including dengue fever and malaria. Boneset is used homeopathically, meaning in very dilute amounts. There is some evidence, though weak, that boneset decreases symptoms associated with influenza.

• Homeopathic medicine is regulated by the U.S. Food and Drug Administration (FDA) and is not currently known to have side effects, due to the very small amounts of active substance used in its preparation. Avoid if allergic or hypersensitive to boneset (Eupatorium perfoliatum), any of its constituents, or related members of the Asteraceae/Compositae family, such as dandelion, goldenrod, ragweed, sunflower, and daisies. Use cautiously in small children, elderly individuals, or individuals suffering from a chronic condition. Use cautiously even in the amounts recommended by manufacturers, as boneset may promote sweating, the production of urine, and catharsis. Avoid with known liver or kidney conditions and in patients who ingest moderate to large amounts of alcohol. Avoid in patients who are pregnant or breastfeeding.

• Bovine colostrum: Bovine colostrum is the pre-milk fluid produced from cow mammary glands during the first 2-4 days after birth. Bovine colostrum confers growth, nutrient, and immune factors to the offspring. Bovine colostrum has shown potential for immune stimulation. However, early evidence has not shown any benefit for treating upper respiratory tract infections, although bovine colostrum may reduce symptoms. Further studies are required before a conclusion can be made.

• Avoid if allergic to dairy products. Use cautiously because toxic compounds, such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), and dichlorodiphenyldichloroethylene (DDE), have been found in human colostrum and breast milk. Thus, it is possible that these agents may be found in bovine colostrum. Avoid with, or if at risk for, cancer. Use cautiously with immune system disorders or atherosclerosis (hardening of the arteries). Use cautiously if taking medications, such as antidiarrheal agents (e.g., Imodium®), insulin, or CNS agents (such as amphetamines or caffeine). Avoid in patients who are pregnant or breastfeeding.

• Chiropractic: Chiropractic care focuses on how the relationship between musculoskeletal structure (mainly the spine) and bodily function (mainly nervous system) affects health. There is currently not enough reliable scientific evidence to conclude the effects of chiropractic techniques on respiratory tract infections.

• Use extra caution during cervical adjustments. Use cautiously with acute arthritis, conditions that cause decreased bone mineralization, brittle bone disease, bone-softening conditions, bleeding disorders, and migraines. Use cautiously with the risk of tumors or cancers. Avoid with symptoms of vertebrobasilar vascular insufficiency, aneurysms, unstable spondylolisthesis, or arthritis. Avoid if taking drugs that increase the risk of bleeding. Avoid in areas of paraspinal tissue after surgery. Avoid in patients who are pregnant or breastfeeding due to a lack of scientific data.

• Cranberry: Limited laboratory research has examined the antiviral activity of cranberry. Further research is warranted in this area.

• Avoid if allergic to cranberries, blueberries, or other plants of the Vaccinium species. Sweetened cranberry juice may affect blood sugar levels. Use cautiously with a history of kidney stones. Pregnant and breastfeeding women should avoid cranberry in higher amounts than what is typically found in foods.

• Garlic: Preliminary reports suggest that garlic may reduce the severity of upper respiratory tract infections. However, this has not been demonstrated in well-designed human studies.

• Avoid if allergic or hypersensitive to garlic or other members of the Lilaceae(lily) family (such as hyacinth, tulip, onion, leek, chive). Avoid with a history of bleeding problems, asthma, diabetes, low blood pressure, or thyroid disorders. Stop using supplemental garlic two weeks before dental, surgical, or diagnostic procedures, and stop using immediately after such procedures to avoid bleeding problems. Avoid in supplemental doses if pregnant or breastfeeding.

• Ginseng: For more than 2,000 years, the roots of ginseng have been valued in Chinese medicine. Ginseng (CVT-E002) may be safe, well tolerated, and potentially effective for preventing acute respiratory infections and illnesses caused by the flu or the respiratory syncytial virus. More study is needed in this area.

• Avoid with a known allergy to plants in the Araliaceae family, such as English ivy. There has been a report of a serious life-threatening skin reaction, possibly caused by contaminants in ginseng formulations.

• Goldenseal: Goldenseal has become a popular treatment for upper respiratory tract infections and is often added to echinacea in commercial herbal cold remedies. Animal and laboratory research suggests that the goldenseal component berberine has effects against bacteria and inflammation. However, due to the very small amount of berberine in most goldenseal preparations, it is unclear whether goldenseal contains enough berberine to have the same effects.

• Avoid if allergic or hypersensitive to goldenseal or any of its constituents, such as berberine and hydrastine. Use cautiously with bleeding disorders, diabetes, or low blood sugar. Avoid in patients who are pregnant or breastfeeding.

• Guided imagery: Therapeutic guided imagery may be used to help patients relax and focus on images associated with personal issues they are confronting. Experienced guided imagery practitioners may use an interactive, objective guiding style to encourage patients to find solutions to problems by exploring their existing inner resources. Biofeedback is sometimes used with imagery to enhance meditative relaxation. Interactive guided imagery groups, classes, workshops, and seminars are available, as are books and audiotapes. Preliminary research in children suggests that stress management and relaxation with guided imagery may reduce the duration of symptoms due to upper respiratory tract infections. Additional research is needed to confirm these results.

• Guided imagery is usually intended to supplement medical care, not to replace it, and guided imagery should not be relied on as the sole therapy for a medical problem. Contact a qualified healthcare provider if mental or physical health is unstable or fragile. Never use guided imagery techniques while driving or doing any other activity that requires strict attention. Use cautiously with physical symptoms that can be brought about by stress, anxiety, or emotional upset, because imagery may trigger these symptoms. If feeling unusually anxious while practicing guided imagery, or with a history of trauma or abuse, speak with a qualified healthcare provider before continuing to practice guided imagery.

• Licorice: Historically, licorice has been used for its expectorant and antitussive effects. The herbal combination product KanJang® has been studied for the treatment of uncomplicated upper respiratory tract infections. Results are mixed, and additional study is needed.

• Avoid with a known allergy to licorice, any component of licorice, or any member of the Fabaceae (Leguminosae) plant family. Avoid with congestive heart failure, coronary heart disease, kidney or liver disease, fluid retention, high blood pressure, or hormonal abnormalities, or in patients taking diuretics. Licorice may cause abnormally low testosterone levels in men or high prolactin or estrogen levels in women. This may make it difficult to become pregnant and may cause menstrual abnormalities.

• Moxibustion: Moxibustion is the application of heat to various points on the body. It is widely used traditionally in China for treatment of upper respiratory tract infections in children, including colds and flu. However, at this time reliable clinical evidence is insufficient.

• Individuals not trained in moxibustion should not perform this procedure on themselves or others. Use cautiously over large blood vessels and thin or weak skin. Avoid with aneurysms, any kind of "heat syndrome," cardiac disease, convulsions or cramps, diabetic neuropathy, extreme fatigue or anemia, fever, inflammatory conditions, allergic skin conditions or ulcerated sores, or skin adhesions. Avoid in patients who are pregnant or breastfeeding. Avoid areas with an inflamed organ, contraindicated acupuncture points, or on the face, genitals, head, or nipples. Avoid in patients who have just finished exercising or taking a hot bath or shower. Use cautiously with elderly people or with large vessels. It is considered not advisable to bathe or shower for up to 24 hours after a moxibustion treatment.

• Propolis: Propolis is a natural flavonoid-rich resin created by bees, used in the construction of hives. Propolis is produced from the buds of conifer and poplar trees, in combination with beeswax and other bee secretions. There is some evidence to support the use of propolis for the prevention or treatment of upper respiratory tract infections in children, although current data are generally inadequate. Further research is needed before a conclusion can be made.

• Avoid if allergic or hypersensitive to propolis, black poplar (Populus nigra), poplar bud, bee stings, bee products, honey, and Balsam of Peru. Severe allergic reactions have been reported. Use cautiously with asthma or gastrointestinal disorders. Avoid in patients who are pregnant or breastfeeding because of the high alcohol content in some products.

• Sorrel: There is currently not enough evidence on the proposed antiviral effects of sorrel. More research is needed.

• Avoid large doses of sorrel, because there have been reports of toxicity and death. This may be because of the oxalate found in sorrel. Many sorrel tinctures contain high levels of alcohol and should be avoided when driving or operating heavy machinery. These sorrel formulations may cause nausea or vomiting when taken with the prescription drugs metronidazole (Flagyl®) or disulfiram (Antabuse®). Avoid in patients who are pregnant or breastfeeding.

• Thymus extract: Preliminary evidence suggests that both intramuscular and oral thymus extract may be useful for reducing the presence of symptoms associated with respiratory tract infections. Additional study is needed.

• Avoid if allergic or hypersensitive to thymus extracts. Use bovine thymus extract supplements cautiously. Avoid use with an organ transplant or other forms of allografts or xenografts. Avoid with thymic tumors, myasthenia gravis (neuromuscular disorder), or untreated hypothyroidism. Avoid if receiving immunosuppressants or hormonal therapy. Avoid in patients who are pregnant or breastfeeding.

• Turmeric: Turmeric is a perennial plant native to India and Indonesia, and it is often used as a spice in cooking. Based on early research, turmeric may help treat various viral infections. However, reliable human studies are lacking in this area. Well-designed trials are needed.

• Avoid if allergic or hypersensitive to turmeric (curcumin), yellow food colorings, or plants belonging to the Curcuma or Zingiberaceae (ginger) families. Use cautiously with a history of bleeding disorders, immune system deficiencies, liver disease, or gallstones. Use cautiously with blood thinners (e.g., warfarin). Use cautiously in patients who are pregnant or breastfeeding.

• Vitamin E: Vitamin E may have a protective effect against colds and influenza. Additional research is needed to better understand the effectiveness of Vitamin E for respiratory infection prevention.

• Caution is advised when taking vitamin E supplements, as adverse effects, including an increase in bleeding, and drug interactions are possible. Vitamin E supplements should not be used in patients who are pregnant or breastfeeding, unless otherwise directed by a doctor.

• Wild indigo: Preliminary evidence has shown immunostimulative properties of wild indigo (Baptisia australis) extracts for respiratory tract infections. However, available clinical studies have been conducted using the combination Esberitox N (Echinacea purpurea radix, Baptisia tinctoria radix, and Thuja occidentalis herba). Additional study is needed using wild indigo alone.

• Avoid if allergic or hypersensitive to wild indigo, its constituents, or members of the Fabaceae family. Use cautiously if taking immunosuppressive agents. Avoid in patients who are pregnant or breastfeeding.

• Fair negative scientific evidence:

• Echinacea: Although there is some evidence that Echinacea may be effective in adults, the research so far suggests that Echinacea may not be helpful for treatment of upper respiratory tract infections in children.

• Avoid in patients who are allergic to echinacea, its constituents, or any members of the Asteraceae/Compositae family (ragweed, chrysanthemums, marigolds, daisies). Use cautiously in patients prone to atopic reactions and in those with hemochromatosis and diabetes. Some natural medicine experts discourage the use of echinacea by people with conditions affecting the immune system, such as HIV/AIDS, some types of cancer, multiple sclerosis, tuberculosis, and rheumatologic diseases (such as rheumatoid arthritis or lupus). Use parenteral preparations of echinacea(no longer approved for use in Germany) cautiously. Use tinctures cautiously with alcoholic patients or in patients taking disulfiram or metronidazole. Avoid using echinacea in patients presenting for anesthesia. Use cautiously in patients who are pregnant or breastfeeding.

Prevention

• Vaccination: An annual flu vaccination may lower the risks of getting a flu infection. Because influenza viruses mutate (change) quickly, new vaccines must be created every year. The flu vaccine is designed to prevent specific strains of flu that are predicted to be the dominant strains for the upcoming flu season. Because H1N1 appeared at the end of the 2008-2009 flu season, the vaccine that was available at the time did not prevent its spread. On September 15, 2009 the U.S. Food and Drug Administration (FDA) announced that it approved four vaccines against the 2009 H1N1 influenza virus, manufactured by CSL Limited, MedImmune LLC, Novartis Vaccines and Diagnostics Limited, and Sanofi pasteur Inc.

• The virus continually undergoes two different types of changes: antigenic drifts and antigenic shifts. Antigenic drift refers to continual, but gradual, genetic changes in the virus. Influenza types A and B undergo antigenic drift. In contrast, antigenic shift refers to drastic genetic changes that occur quickly. Antigenic shift results in new influenza A virus subtypes in humans. These changes occur as a result of genetic reassortment, or the rearrangement of viral genes, when two different virus strains infect a cell at the same time.

• Traditionally, vaccines have been created through reassortment, but advancements in reverse genetics may change that. Reverse genetics enables viruses to be created completely from DNA material.

• There are two types of vaccines, including an injection (flu shot) and a nasal-spray vaccine.

• The flu shot is an inactivated vaccine (containing killed virus) that is given with a needle. The flu shot is approved for use in people six months of age and older, including healthy people and people with chronic medical conditions such as diabetes, asthma, and heart disease.

• Target populations for the flu shot include children aged six months to five years, adults that are in close contact with children aged six months to five years, such as teachers and day care workers, people 50 years of age and older, healthcare workers, all caregivers of high-risk people, such as those with HIV/AIDS or cancer, and people with chronic health conditions, such as asthma, as well as pregnant women.

• The best period to receive any of the influenza vaccines is soon after the vaccine becomes available in the fall of each year. Flu shots are given yearly to protect individuals against the strain of influenza prevalent for a particular year.

• The nasal-spray flu vaccine is a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for "Live Attenuated Influenza Vaccine"). The nasal flu vaccine is approved for use in healthy people five to 49 years of age who are not pregnant.

• Flu Mist® is the first nasal-spray vaccine for influenza and has been approved by the U.S. Food and Drug Administration (FDA). The live virus is frozen until use. Healthcare professionals recommend thawing it in a refrigerator. It should not be refrozen after thawing because of decreased vaccine potency. If the nasal vaccine is not available, the injection can be used where available.

• A prescription is needed for the influenza vaccine (both injection and nasal forms) and is available from a doctor or various flu clinics.

• Healthcare professionals recommend that some individuals should not be vaccinated. These include people who have a severe allergy to chicken eggs, people who have had a severe reaction to an influenza vaccination in the past, people who developed Guillain-Barre syndrome (a disorder where the immune system attacks the nervous system) within six weeks of getting an influenza vaccine previously, children less than six months of age (the influenza vaccine is not approved for use in this age group), and people who have a moderate or severe illness with a fever (it is recommended that these patients wait until symptoms lessen to get vaccinated).

• Cleanliness: Clean the hands thoroughly and often to prevent transmission of the influenza virus. Carrying a bottle of alcohol-based hand rub containing at least 60% alcohol is advised for times when soap and water are not available. These gels kill most germs and are safe for older children to use themselves. Many healthcare professionals recommend not overusing antibacterial soaps and cleansers. The skin contains natural bacteria that can be harmed with repeated use of soaps. Keeping kitchen and bathroom countertops clean, especially when someone in the family has the flu, is important. Wash children's toys before and after play when a cold is present in the house. Sneezing and coughing into tissues keeps the viruses from spreading. Used tissues should be discarded right away. A face mask can be worn to protect an individual from the influenza virus and to keep an infected person from transmitting the virus.

• Avoiding prolonged contact: Healthcare professionals recommend avoiding close, prolonged contact with anyone who has the flu.

• Careful travel: Traveling to Southeast Asia or to any region with bird flu outbreaks puts an individual at risk. Healthcare professionals recommend that people avoid domesticated birds such as pigeons, avoid open-air markets, wash their hands, watch children carefully, and stay clear of raw eggs.

• Antiviral prophylaxis: Antiviral medications may be taken for prophylaxis (prevention). However, this is generally reserved for certain individuals such as healthcare workers who come in contact with many people and may be routinely exposed to novel H1N1. Antiviral prophylaxis is generally discouraged for others. Healthcare officials are worried that antiviral overuse may lead to drug resistance in novel H1N1 or other influenza strains. Indeed, some isolates of H1N1 virus have shown resistance to commonly used antiviral medications.

Author Information

• This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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