What is seasonal influenza? |

Definition

Seasonal influenza (the flu) is a viral infection that affects the
respiratory system. It can cause mild to severe illness and sometimes death. To
avoid getting the flu, one should get vaccinated every year.

Causes

The flu is caused by the influenza virus. Each winter, the virus
spreads around the world. The strains usually differ from one year to the next.
The two main kinds of influenza virus are type A and type B.

A person who is infected with the virus may sneeze or cough, releasing droplets into the air. If another person breathes in infected droplets, he or she can become infected. A person can also become infected by touching a contaminated surface, which risks the transfer of the virus from one’s hand to one’s mouth or nose.

Risk Factors

Factors that increase the chance of getting the flu include living or working
in crowded group conditions, such as in nursing homes, schools, day-care centers,
and the military. Factors that increase the risk of developing complications from
flu include being pregnant; having recently given birth; having diabetes or
chronic lung, heart, kidney, liver, nerve, or blood conditions; and being in a
chronic care facility. Other persons at risk are those who have a weakened immune
system, such as people infected with the human immunodeficiency
virus and people taking immunosuppressive drugs.

Also at higher risk are children younger than five years of age, adults ages sixty-five years and older, and people younger than the age of nineteen years (and who are on a long-term aspirin regimen).

Symptoms

A person with the flu is infectious beginning one day before his or her own symptoms start and up to five days (sometimes more) after becoming sick. This means that a person who has the flu could infect others before knowing that he or she is sick.

Symptoms usually start abruptly and include a high fever and chills; severe muscle aches; severe fatigue; a headache; decreased appetite or other gastrointestinal symptoms, such as nausea, vomiting, and diarrhea (more common in children than in adults); a runny nose and nasal congestion; sneezing; watery eyes or conjunctivitis; a sore throat; a cough (that lasts for two or more weeks); and swollen lymph nodes in the neck. The ill person might start to feel better in seven to ten days but may still have a cough and feel tired.

Screening and Diagnosis

A doctor will ask about symptoms and medical history to determine a person’s diagnosis of the flu. In some cases, the doctor may take samples from the person’s nose or throat to confirm the diagnosis.

Treatment and Therapy

Treatment for the flu includes antiviral prescription medicines. Most people
with the flu do not need antiviral medicine, but persons who do are those who are
in a high-risk group or who have a severe illness (such as breathing problems).
Antiviral medicines, which generally help relieve symptoms and shorten the time a
person is sick, should be taken within forty-eight hours of the first symptoms.
These medicines include zanamivir (Relenza), which may worsen a patient’s asthma
or chronic
obstructive pulmonary disease (COPD), and oseltamivir
(Tamiflu), amantadine (Symmetrel), and rimantadine (Flumadine), all three of which
are ineffective against some kinds of seasonal influenza viruses. Furthermore,
oseltamivir (and perhaps zanamivir) may increase the risk of self-injury and
confusion shortly after being ingested, especially by children. One should monitor
children closely for signs of unusual behavior.

Other forms of treatment include rest, which will help the body fight the flu;
fluids, including water, juice, and caffeine-free tea; over-the-counter pain
relievers, which are used to control fever and to treat aches and pains (adults
can use acetaminophen or ibuprofen); and decongestants, which are available as pills or as nasal sprays.
One should not use a nasal spray for more than three to five days. When stopping,
the patient may experience an increase in congestion called a rebound.

Prescription cough medicines and cough drops also are available, as are
over-the-counter cough and cold medicines. These include decongestants,
expectorants, antihistamines, and cough suppressants. However, these
should not be used to treat infants or children less than two years of age. Rare
but serious side effects have been reported, including death, convulsions, rapid
heart rates, and decreased levels of consciousness. Serious side effects have also
been reported in children between the ages of two and eleven years.

Herbal treatments, such as elderberry extract, may reduce flu symptoms. Researchers have found that products such as Sambucol and ViraBLOC, which contain elderberry, decrease symptoms in some studies. Herbal remedies, however, are not regulated by the government, so care should be taken in using them. The herbal supplements may not have the same ingredients as those studied and may contain impurities.

Prevention and Outcomes

To prevent getting the flu, one should get vaccinated and do so each year because the virus changes every season. The best time to get vaccinated is between the months of September and January (or later, because the flu season can last longer). Two forms of the vaccine are available: a flu shot (injection) and a nasal spray (FluMist). The nasal spray is approved for healthy (and nonpregnant) people between the ages of two and forty-nine years.

People who care for others with severely weakened immune systems should not get
the nasal spray; instead they should get the flu shot. The flu shot is not
effective against H1N1 flu, however, which has its own vaccine.

Persons who want to reduce their risk of the flu should consider the vaccine. It takes about two weeks for the vaccination to protect against the flu. Those who should get a yearly flu vaccine include children ages six months to eighteen years; parents, babysitters, and caretakers of children less than six months of age (because these children are too young to be vaccinated); adults older than fifty years of age (because vaccination in this age group likely reduces hospitalizations and deaths); those living or working in nursing homes and long-term care facilities; those with chronic medical conditions such as asthma; those with diabetes, kidney problems, hemoglobin abnormalities, or immune system problems; women who are pregnant; health care workers; and those living with someone who is at high risk for complications from the flu.

People who should not be vaccinated are those who are severely allergic to chicken eggs, those who had a severe reaction to vaccination in the past, and children less than six months of age. Persons who are sick and have a fever should discuss vaccination with a medical provider.

There are general measures one can take to reduce the risk of getting the flu. These measures include washing one’s hands often, especially after contacting someone who is sick (rubbing alcohol-based cleaners on one’s hands is also helpful), and avoiding close contact with people who have respiratory infections. The flu can spread starting one day before and ending seven days after symptoms appear.

Other preventive measures are to cover one’s mouth and nose with a tissue when coughing or sneezing, and then throwing away the tissue after use; avoid spitting; avoid sharing drinks or personal items; avoid biting one’s nails; and avoid putting one’s hands near one’s eyes, mouth, or nose. Another measure is to keep surfaces clean by wiping them with a household disinfectant.

One should consult a doctor about lowering the risk of getting the flu (also
about lowering the risk for children who are one year of age or older) with
antiviral medications (such as zanamivir). Antiviral medications are helpful for
persons at high risk for the flu and for those who were only recently vaccinated
(within the past two weeks), especially if the flu is spreading in one’s
community; for persons at high risk for the flu and who cannot have the vaccine;
and for persons not vaccinated and who have repeated close contact with persons
(such as family members) who are at high risk for the flu. Persons (such as the
elderly, infants, and persons with cancer) who are at risk for complications of
the flu and who live with someone who has the flu should get antiviral
medications.

Persons who have the flu should take the following steps to avoid spreading the virus to others: Before returning to school or work, one’s fever should be gone for at least twenty-four hours without the help of fever-reducing medicine. This could take up to seven days after symptoms first appear. A sick person who cannot avoid close contact should cover his or her mouth and nose with a face mask.

Bibliography

Belshe, R. B., et al. “Live Attenuated Versus Inactivated Influenza Vaccine in Infants and Young Children.” New England Journal of Medicine 356 (2007): 685-696. Available through DynaMed Systematic Literature Surveillance at http://www.ebscohost.com/ dynamed.

Centers for Disease Control and Prevention. “Home Care Guidance: Physician Directions to Patient/Parent.” Available at http://www.cdc.gov/h1n1flu/ guidance_homecare_directions.htm.

_______. “Key Facts About Seasonal Influenza (Flu) and Flu Vaccine.” Available at http://www.cdc.gov/flu/keyfacts.htm.

Cowling, B. J., et al. “Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households: A Cluster Randomized Trial.” Annals of Internal Medicine 151, no. 7 (2009): 437-446. Available through DynaMed Systematic Literature Surveillance at http://www.ebscohost.com/dynamed.

EBSCO Publishing. DynaMed: Influenza. Available through http://www.ebscohost.com/dynamed.

_______. Health Library: Flu. Available through http://www.ebscohost.com.

Mandell, Gerald L., John E. Bennett, and Raphael Dolin, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 7th ed. New York: Churchill Livingstone/Elsevier, 2010.

Nichol, K. L., et al. “Effectiveness of Influenza Vaccine in the Community-Dwelling Elderly.” New England Journal of Medicine 357 (2007): 1373-1381. Available through DynaMed Systematic Literature Surveillance at http://www.ebscohost.com/dynamed.

Smith, N. M., et al. “Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices.” Morbidity and Mortality Weekly Report 55 (2006): 1-42.

U.S. Food and Drug Administration. “Public Health Advisory: FDA Recommends that Over-the-Counter (OTC) Cough and Cold Products Not Be Used for Infants and Children Under Two Years of Age.” Available at http://www.fda.gov/safety/medwatch.

_______. “2008 Safety Alerts for Drugs, Biologics, Medical Devices, and Dietary Supplements: Tamiflu (Oseltamivir Phosphate).” Available at http://www.fda.gov/safety/medwatch.

World Health Organization. “Influenza Vaccines.” Weekly Epidemiological Record 28, no. 77 (2002): 229-240.

Zakay-Rones, Z., et al. “Inhibition of Several Strains of Influenza Virus In Vitro and Reduction of Symptoms by an Elderberry Extract (Sambucus nigra l.) During an Outbreak of Influenza B Panama.” Journal of Alternative and Complementary Medicine 1 (1995): 361-369.

_______. “Randomized Study of the Efficacy and Safety of Oral Elderberry Extract in the Treatment of Influenza A and B Virus Infections.” Journal of International Medical Research 32, no. 2 (2004): 132-140.