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What is the flu?
Influenza, or flu, is a respiratory infection caused by several flu viruses. Flu viruses are classified as types A, B, and C; type A has a number of subtypes. The flu is not the same as the common cold, nor is it related to what is commonly called the "stomach flu." Seasonal flu is the term used to refer to the flu outbreaks that occur yearly, mainly in the late fall and winter.
The flu differs in several ways from the common cold. For example, people with colds rarely get fevers or headaches or suffer from the extreme exhaustion that flu viruses cause. The most familiar aspect of the flu is the way it can "knock you off your feet" as it sweeps through entire communities.
Seasonal flu outbreaks usually begin suddenly and occur mainly in the late fall and winter. The disease spreads through communities, creating an epidemic - the number of cases peaks in about 3 weeks and subsides after another 3 or 4 weeks. Half of the population of a community may be affected; schools are an excellent place for flu viruses to attack and spread. Most people who get the flu get better within a week (although they may have a lingering cough and tire easily for a while longer).
Small, continuous changes happen in type A and type B influenza as the virus makes copies of itself, frequently enough to make the new strain of virus often unrecognizable to the human immune system. For this reason, a new flu vaccine must be produced each year to combat that year's prevalent strains.
The normal treatment for flu is rest, plenty of liquids, and acetylsalicylic acid* (ASA), ibuprofen, or acetaminophen to fight fever. Children and teenagers with flu shouldn't take ASA or other salicylates (medications related to ASA, such as salsalate or magnesium salicylate). The combination of influenza and ASA is linked to Reye's syndrome, a rare but serious condition affecting the brain and liver. Very few over-the-counter cold or flu medicines contain ASA or other salicylates. Ask your doctor or pharmacist about this.
Antibiotics are not effective against viral infections like flu and the cold, but they are prescribed for complications such as bacterial infections.
Each spring, a worldwide network of physicians and testing labs decide which flu strains are likely to cause trouble, and they design that year's vaccine accordingly. The vaccine gives resistance to the type B strain and the two type A strains that are expected to predominate in the coming flu season.
The vaccine is usually over 80% effective in preventing the seasonal flu in healthy adults. It's given to anyone classified as high-risk, to health workers, and to anyone who wants to avoid the flu.
High risk groups for seasonal flu include:
- those aged 65 years or older
- people with chronic heart, lung, or metabolic disorders (including diabetes)
- those with chronic kidney disease, anemia, a weakened immune system, or asthma
- residents of nursing homes
- children receiving long-term ASA therapy who may be at risk of developing Reye's syndrome
- children six months or older with respiratory disorders
Sometimes, as in the 1997 to 1998 flu season, a new mutation appears after the year's vaccine has been prepared and it's too late to change it. Fortunately, so far the new strains haven't been different enough to completely bypass the resistance offered by the vaccine.
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