INFLUENZA

DEFINITION

Influenza is a highly infectious disease that affects the respiratory (breathing) tract. It is also known as the flu or grippe. The disease is caused by a virus. When inhaled, the virus attacks cells in the upper part of the respiratory system and causes symptoms such as fatigue, fever and chills, a hacking cough, and body aches. Influenza can also lead to other, more serious infections.

The disease known as stomach flu is not really a form of influenza. The influenza virus normally does not attack the stomach or intestines. Stomach flu is instead caused by other organisms, such as the salmonella or E. coli bacteria.

DESCRIPTION

The flu is often confused with the common cold (see common cold entry), but it is actually much more serious. The annual death toll due to influenza and its complications averages twenty thousand in the United States alone. Sometimes, a flu epidemic sweeps across a wide part of the world, killing large numbers of people. An epidemic is a sudden, rapid spread of a disease through a large geographical area. In 1918–19, a form of influenza known as the Spanish flu spread throughout the world. The death toll from the epidemic was estimated at twenty million to forty million people. About five hundred thousand of those deaths occurred in the United States.

Influenza outbreaks occur on a regular basis. An influenza epidemic occurred in 1957 and again in 1968. The first of these outbreaks was known as the Asian flu. The second was called the Hong Kong flu. About seventy thousand Americans died of the Asian flu and about thirty-four thousand from the Hong Kong flu.

Influenza has been known for more than 2,500 years. The ancient Greek physician Hippocrates was one of the earliest writers to describe the condition. Throughout most of history, people blamed the disease on a number of factors, including various kinds of bacteria and "bad air." In 1933, however, researchers found the real cause of the disease: a virus.

Three types of influenza viruses have now been discovered: types A, B, and C. Type A virus can infect many different kinds of animals, including humans, pigs, horses, and birds. Viruses B and C infect only humans. Influenza A is responsible for most cases of the disease in humans. Types B and C are less common and produce a milder form of infection.

CAUSES

Influenza is caused by the transmission of a flu virus from an infected person to an uninfected person. The virus can be transmitted by sneezing, coughing, sharing of eating and drinking utensils, and direct contact.

SYMPTOMS

The first symptoms of infection appear one to four days after the virus has entered a person's body. They include headache, dry cough, and chills. These symptoms are followed quickly by overall achiness and a fever that may run as high as 104°F (40°C). As the fever declines, nasal (nose) congestion and a sore throat become noticeable. The flu leaves an individual very tired and weak. A person with the flu may not return to normal for several days or even a few weeks.

A flu infection often leads to more serious complications. These complications are often caused by bacteria that get into the lower respiratory tract. The signs of a secondary (follow-up) infection often appear just as the person seems to be recovering from the flu. These signs include a high fever, chills, chest pains, and a cough that produces a thick, yellowish sputum (discharge from the throat). If these symptoms appear, medical treatment should be sought.

A magnified image of an influenza virus budding on the surface of an infected cell. (Reproduced by permission of

CNRI/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc.

)

Secondary infections also affect the sinus or ears. The flu can also worsen heart and lung problems and certain other chronic diseases. For this reason, an attack of the flu can be especially serious for elderly people.

DIAGNOSIS

The symptoms of a flu infection are familiar to all medical workers. Doctors and nurses can usually diagnose the disease simply by examining a patient. Tests are available to identify the flu virus and the various forms in which it occurs, but these tests are seldom needed for the purpose of diagnosis. Some tests may be necessary to diagnose secondary infections. For example, a doctor may take a throat culture to identify a throat infection.

TREATMENT

Influenza cannot be cured. The usual course of action is to allow the body to heal itself. Various treatments are available to help relieve symptoms, however. For example, a person should get plenty of bed rest and drink lots of fluids. A steam vaporizer can make breathing easier. Painkillers help relieve the aches and pains of the flu. Children should not be given aspirin, however. Aspirin has been shown to cause a rare condition known as Reye's syndrome (see Reye's syndrome entry), which can be fatal.

Flu patients often do not feel hungry. However, they should be encouraged to eat as normally as possible. Patients should not try to return to normal activities too soon. Overactivity can cause a return of the infection or secondary infections.

Drugs

Patients sometimes ask their doctor for antibiotics to cure the flu. But antibiotics have no effect on the flu virus. They can be used, however, to treat secondary infections.

There are many over-the-counter (nonprescription) medications for the treatment of flu symptoms. Medications that include alcohol should be avoided, however. Alcohol has a tendency to reduce the amount of water in a person's body. The best medicine is often an analgesic (painkiller), such as acetaminophen (pronounced uh-see-tuh-MIN-uh-fuhn, trade name Tylenol) or naproxen (pronounced nuh-PROKS-suhn, trade name Aleve).

Two antiviral drugs are available for the treatment of influenza in the United States. They are recommended for people with weak immune systems or people who are allergic to the flu vaccine. These two drugs are amantadine hydrochloride (pronounced uh-MANT-uh-deen HIE-druh-KLOR-ide, trade names Symmetrel, Symadine, Amantadine-hydrochloride) and rimantadine hydrochloride (pronounced ruh-MAN-tuh-deen HIE-druh-KLOR-ide, trade name Flumandine). Both drugs are effective against type A viruses only. These should be used with care because they both have serious side effects.

Alternative Treatment

A number of alternative treatments have been recommended for the treatment of influenza. In most cases, there is little scientific evidence for the success of these treatments.

A pharmacy worker in Russia wears a respiratory mask while serving customers to protect herself from a flu epidemic in 1999. (Reproduced by permission of

AP/Wide World Photos

)

• Acupuncture and acupressure. Practitioners believe that these two techniques can stimulate natural resistance, relieve nasal congestion and headaches, reduce fever, and soothe coughs. Acupuncture is a Chinese therapy that uses fine needles to pierce the body; acupressure involves applying pressure to certain points in the body.
• Aromatherapy. Aromatherapists recommend gargling daily with one drop each of tea tree oil and lemon in a glass of warm water. Two drops of tea tree oil in a hot bath may help ease some symptoms. A few drops of the oils of eucalyptus (pronounced yoo-kuh-LIP-tus) or peppermint can be added to a steam vaporizer. They may help clear chest and nasal congestion.
• Herbal remedies. Echinacea (pronounced ek-i-NAY-see-uh) has been recommended to improve a person's immune system. Certain herbs, such as goldenseal and garlic, are thought to be able to kill viruses. A number of herbs can be used to treat the symptoms of influenza. For example, boneset may counteract aches and fever, and yarrow or elder flower may combat chills.

Often confused with a common cold, the flu is actually a much more serious infection. It causes aches, fever, and leaves an individual very tired and weak. (© 1991

Keith

. Reproduced by permission of

Custom Medical Stock Photo

.)

• Homeopathy. Homeopathic practitioners recommend a variety of herbs to treat the symptoms of the flu. These include Gelsemium (pronounced jel-SEE-mee-uhm) for the treatment of chills, headache, and nasal congestion; Bryonia (pronounced brie-OH-nee-uh) for muscle aches, headaches, and dry cough; and poison ivy for restlessness, chills, hoarseness, and achy joints.
• Hydrotherapy. Taking a hot bath may help a person recover from the flu more quickly: The higher a person's body temperature, the more quickly the virus is likely to die. Hydrotherapists recommend that a person drink a cup of yarrow or elder flower tea while taking a bath: These herbs cause a person to sweat.
• Vitamins. Some people believe that large doses of vitamin C can help prevent the flu. They suggest increasing the amount of vitamin C once a flu infection has started.

PROGNOSIS

Healthy people under the age of sixty-five seldom experience serious, long-term consequences from a flu infection. Older people and people who are chronically ill are at risk for secondary infections, but they often recover from the flu quickly and completely. The high recovery rate from influenza should not be misleading. The infection can still be very serious. About 1 in 1,000 cases will actually lead to the patient's death.

PREVENTION

Vaccines are now available to help prevent influenza infections. The composition of these vaccines is changed every year. A vaccine is designed to protect people against three specific influenza viruses—the viruses thought to be most likely to infect people in a given year. Scientists may or may not make good guesses as to the "most likely" flu viruses. When they are successful, the vaccine can be 70 percent to 90 percent effective in people under the age of sixty-five.

The U.S. Centers for Disease Control and Prevention recommend that people get a flu vaccine injection each year before the flu season starts. In the United States, flu season usually runs from late December to early March. Adults usually need only one dose of the vaccine. Children under the age of nine who have not previously been vaccinated will need two doses one month apart.

Side effects from influenza vaccinations are rare. People who have never had influenza may experience about two days of discomfort. They may have a slight fever, feel tired, and experience achy muscles.

Certain people should not have influenza vaccinations. They include infants under the age of six months and people who are allergic to eggs. These people can be given the antiviral drugs described if necessary. However, certain groups of people are strongly advised to be vaccinated. These groups include:

• All people over the age of sixty-five
• Residents of nursing homes and other health-care facilities, regardless of age
• Adults and children who have chronic heart or lung problems, such as asthma (see asthma entry)
• Adults and children who have other kinds of chronic diseases, such as diabetes (see diabetes mellitus entry), severe anemia (see anemias entry), blood disorders, or kidney problems
• Children and teenagers who are on long-term aspirin therapy
• Women who are in the last two-thirds of their pregnancy and women who are nursing
• People with weakened immune systems, such as AIDS patients (see AIDS entry), people who have received organ transplants, and patients receiving various types of medical treatments, such as chemotherapy or radiation therapy
• Anyone who has regular contact with people in any of the above groups, such as teachers, health-care personnel, and family members
• Travelers to foreign countries

An individual need not be in one of the at-risk groups to receive a flu vaccination. Anyone who wants to avoid the discomfort of an influenza attack may receive the vaccine.

FOR MORE INFORMATION

Books

Brody, Jane E. Jane Brody's Cold and Flu Fighter. New York: W. W. Norton & Company, 1995.

Inlander, Charles B., and Cynthia K. Moran. 77 Ways to Beat Colds and Flu. New York: Walker & Company, 1994.

Silverstein, Alvin, Virginia Silverstein, and Robert Silverstein. Common Cold and Flu. Hillside, NJ: Enslow Publishers, Inc., 1994.

Periodicals

Novitt-Moren, Anne. "Holiday's Biggest Spoilers: Colds and Flu." Current Health (December 1997): p. 6.

Saul, Helen. "Flu Vaccines Wanted: Dead or Alive." New Scientist (February 18, 1995): p. 26.

Organizations

Centers for Disease Control and Prevention. 1600 Clifton Road NE, Atlanta, GA 30333. (888) CDC-FACTS. http://www.cdc.gov.