Influenza

Influenza, commonly known as "the flu," is a contagious respiratory disease caused by the influenza virus. The virus attacks the respiratory tract -- nose, throat and lungs.

In the United States, the flu season can peak anywhere from late December through March. Millions of people in the United States get the flu each year.


The myth of the "stomach flu"
Many people use the term "stomach flu" as a general way to describe illnesses with nausea, vomiting or diarrhea. This isn't correct. Although vomiting, diarrhea and being "sick to your stomach" sometimes can be related to the flu -- particularly in children -- these problems are rarely the main symptoms of influenza. The flu is a respiratory disease. It's not a stomach or intestinal disease.

Transmission
The flu typically spreads through contact with infected respiratory droplets coughed or sneezed into the air. The virus can enter your nose, throat or lungs and begin to multiply, eventually causing flu symptoms. Less often, you can catch the flu by touching a contaminated surface, such as a doorknob, and then touching your nose or mouth.
Adults can spread the flu virus from one day before symptoms appear through three to seven days after symptoms appear. Children can spread the virus even longer. Even those who don't have symptoms can spread the virus to others during this time.


Signs and symptoms
Symptoms of the flu typically begin one to four days after the virus enters your body. When symptoms appear, they often strike suddenly. You may notice:
fever
body aches
dry cough
fatigue (possibly extreme)
headache
sore throat
nasal congestion
The fever and body aches can last three to five days. And, the cough and lack of energy may last for two or more weeks.

Children may have additional gastrointestinal symptoms, such as nausea, vomiting and diarrhea. These symptoms are uncommon in adults.


Diagnosis
It's difficult to distinguish the flu from other viral or bacterial respiratory illnesses based on symptoms alone. For a proper diagnosis, the doctor will ask questions about your medical history and do a physical exam.
In some cases, various diagnostic tests may be done to help make treatment decisions. During a respiratory illness outbreak, testing can help the doctor determine whether influenza is the cause of the outbreak.

Samples of respiratory secretions may be taken from your nose or throat within the first four days of illness. With rapid influenza tests, results are available within 30 minutes to 24 hours. Most of these tests are about 70 percent accurate in detecting influenza. More accurate results are likely with a viral culture, but the results may not be available for three to 10 days.

Blood samples also can be tested for antibodies to the influenza virus. One sample is taken during the first week of illness, and a second sample is taken two to four weeks later. If antibody levels increase from the first to the second sample, an influenza infection is likely. The amount of time needed for the diagnosis makes the test impractical when a more rapid diagnosis is needed.

During suspected outbreaks of the flu, testing some samples with both a rapid test and a viral culture can help doctors determine the influenza subtypes and strains causing illness, as well as monitor new strains that may need to be included in the next year's influenza vaccine. A viral culture also can help doctors identify other causes of illness.


Treatment
For healthy adults, most cases of the flu can be left to run their course without treatment. To ease your symptoms:
Get plenty of rest.
Drink plenty of liquids.
Don't drink alcohol or use tobacco.
Take over-the-counter medication to relieve individual symptoms, as recommended by your doctor.
Note: Never give aspirin to children or teenagers who have flu-like symptoms -- particularly fever -- without consulting the doctor. It may cause a rare but serious illness known as Reye's syndrome. (If your child is taking aspirin therapy for a medical condition, talk to the doctor before discontinuing it.)

In some cases, antiviral medications may be prescribed to reduce the length or severity of the illness -- particularly for those who have the highest risk of complications, including young children, pregnant women, adults ages 65 or older, and people who have chronic medical conditions.

When taken within the first two days of illness, the antiviral medications zanamivir or oseltamivir may reduce the duration of the flu by about one day.

Zanamivir (Relenza, for example) is an inhaled medication that must be used with caution by people who have asthma or chronic obstructive pulmonary disease. The medication may cause the airways to suddenly grow smaller, which can lead to difficulty breathing. Other side effects may include nasal and throat discomfort

Oseltamivir (Tamiflu, for example) is an oral medication. Side effects include nausea and vomiting.

These medications are meant to treat the flu virus. They're not effective for other viruses that can cause similar symptoms or bacterial infections that can develop as complications of the flu.

Note: The Centers for Disease Control and Prevention (CDC) recommends that amantadine and rimantadine, two other antiviral medications used in the past to treat flu, not be used for the remainder of the 2005-2006 flu season. Laboratory testing of flu viruses isolated this season has shown that many of the viruses are resistant to these two medications, making them ineffective.


Complications
Most people recover from the flu within one to two weeks. For some people, however, the flu can cause life-threatening complications, such as pneumonia. Sadly, about 36,000 people die from flu-related complications in the United States every year.
Other complications may include bronchitis, sinus infections and ear infections. The flu can also aggravate chronic health problems, such as asthma and congestive heart failure.

Those at highest risk for flu-related complications include:

children ages 6 months to 23 months
children ages 6 months to 18 years who are on long-term aspirin therapy (based on the increased risk of developing Reye's syndrome after a viral infection such as the flu)
anyone who has a chronic heart (not just high blood pressure) or lung condition, such as asthma
anyone who has other chronic diseases that needed regular medical care or hospitalization the previous year, including those who have impaired immune systems (due to cancer, HIV or long-term steroid therapy), kidney problems, diabetes or other metabolic diseases; or those with abnormal red blood cells, such as people who have sickle cell disease)
anyone who has any neuromuscular condition (such as a seizure disorder or spinal cord injury) that may affect the ability to breathe or manage respiratory secretions
women who are pregnant during the flu season
adults age 50 or older (About 26 percent of adults ages 50 to 64 have chronic medical conditions that increase the risk for flu-related complications. All adults ages 65 and older are more at risk for complications, whether chronic medical conditions are present or not.)
residents of nursing homes and other long-term care facilities that house people of any age who have long-term illnesses
If you fall into one of these risk groups, consult your doctor if you suspect you have the flu.


Pregnancy-specific information
Again, the risk of flu-related complications is higher for women who are pregnant during the flu season (usually November to March). To protect yourself from the flu, ask your doctor about a flu shot. The flu vaccine is safe for you and your developing baby at any point during your pregnancy.

Senior-specific information
Older adults have a higher risk of flu-related complications. More than 90 percent of deaths from flu-related pneumonia are among adults age 65 and older.

Prevention
To prevent the spread of respiratory illnesses such as the flu, follow these recommendations from the CDC:
Avoid close contact with people who are sick.
If possible, stay home from work, school, and errands when you're sick to prevent others from becoming ill.
Wash your hands often.
Cover your nose and mouth with a tissue when coughing or sneezing. Promptly dispose of used tissues.
Try not to touch your eyes, nose or mouth. (Germs often spread when you touch a contaminated object or surface and then touch your eyes, nose or mouth.)
Practice other good health habits: Get plenty of sleep, be physically active, manage your stress, drink plenty of fluids, and eat healthfully.
Ask your doctor about a yearly flu shot.
The inactivated influenza vaccine (flu shot) is recommended annually for people who are at risk of serious influenza or its complications and for people who can spread influenza to those at high risk. Because there were concerns about a shortage of flu shots for the 2005-2006 season, the CDC recommended that the following groups receive priority until late fall 2005:

evacuees from Hurricane Katrina age 6 months and older who are living in crowded conditions
people ages 65 and older
residents of long-term care facilities
people ages 2 years to 64 who have a chronic health condition (heart disease or diabetes, for example) or a weak immune system (due to cancer or HIV, for example)
children ages 6 months to 23 months
pregnant women
health-care workers who provide direct patient care
household contacts and out-of-home caregivers of children younger than age 6 months
An annual flu shot continues to be recommended for the following groups:

adults ages 50 and older
children ages 6 months to 18 years on long-term aspirin therapy (A link exists between Reye's syndrome and aspirin use following a viral infection such as the flu.)
people who have any neuromuscular condition (such as a seizure disorder or spinal cord injury) that may affect their ability to breathe or manage respiratory secretions
those who are in contact with other children or adults listed in the priority group above
people who provide essential community services (such as firefighters and members of the police force)
people traveling to the southern hemisphere between April and September, or the tropics at any time
people who live in dormitories or in other crowded conditions
anyone who wants to reduce the risk of getting the flu
Note: Other healthy people ages 5 years through 49 who aren't pregnant (including health care workers and household contacts of people at high risk for influenza complications) are encouraged to be vaccinated with the live, intranasal vaccine, especially when supplies of inactivated vaccine are limited.

If your doctor runs out of the vaccine, ask if it's available elsewhere. Ask your doctor about antiviral medications to prevent or control the flu.