What is the flu?

The Flu, Explained

What is the flu? The flu, or influenza, is a virus that hits the United States every year in the late fall and winter. There are different strains of the flu virus, and usually a different strain predominates every year. The flu is transmitted like the common cold, and symptoms include fever, headache, body ache, sore throat, vomiting, diarrhea, stuffy nose, runny nose, cough, and so forth. You name it, the flu can probably cause it. It is usually diagnosed by observation of the various symptoms. There is a nasal swab test that can confirm whether a person’s illness is the actual flu. The vast majority of flu cases are uncomfortable but pass without consequence.

A moderate course of the flu involves some sort of complication that requires treatment, such as vomiting (treated with anti-nausea meds), severe body aches and fever (treated with ibuprofen), sinus headache, congestion and cough (treated with over-the-counter cough and cold meds), or bacterial compliction such as pneumonia that needs antibiotics. Most people recover without any long-term problems. Antiviral medications (approved for ages one year and older), if started within forty-eight hours of the first symptoms, can make the flu milder. But because most people don’t seek medical care for the flu in the first two days of illness, most people don’t receive these meds.

Severe cases occur when a person suffers complications that require hospitalization, such as dehydration (treated with intravenous fluids) or severe pneumonia (requiring antibiotics and oxygen). Such cases may worsen, despite treatment, and require life support in an intensive care unit. Very rarely, the flu can cause infection or inflammation of the heart, lungs, brain, or other organs, which can be fatal.

Every year I hear on the news that this coming flu season is supposed to be “the worst flu season ever!” But as far as I can tell, almost every flu season has been about the same since I became a doctor. One of these years, the doomsayers may be right. Virtually all cases of the flu in infants, children, and young adults pass without consequence. But given the sheer volume of cases each year, there are bound to be complication in a certain number of people. There is an average of 1000,000 hospitalizations and about 1,500 reported fatalities from the flu every year in the United States. However, the CDC believes that the actual number of flu deaths each year is closer to 36,000. Why is the discrepancy between these two numbers?

The most commonly used source of flu data comes from the Morbidity and Mortality Weekly Report (MMWR) database. The MMWR reports deaths from the flu and from pneumonia in the same group even though most of the cases of pneumonia in the same group even though most of the cases of pneumonia are bacterial and have nothing to do with the flu. This number is usually around 36,000. Admittedly, some cases of bacterial pneumonia are likely triggered by influenza (especially in the elderly), but we don’t know how many. Consequently, every year, the press and many medical organizations warn that “36,000 people die every year from the flu, most of them infants and the elderly.” Such statements give people the false impression that thousands of infants, and tens of thousands of elderly, are killed each year by the flu.

When is the flu vaccine given?

When the flu vaccine first came out, it was recommended only for certain people with underlying health conditions. Then we started using it in infants (considered at high risk for the disease). Now the flu vaccine is officially recommended for all children six months through eighteen years and all adults of any age, to be given every year at the start of flu season (usually around October).

The first year a flu vaccine is given to kids eight years and younger, 2 doses (one month apart) are needed to make the vaccine work well. In subsequent years, only 1 dose is needed. It is recommended that any child eight or less who has only ever had 1 dose in a flu season receive 2 doses during the next season. Kids nine and older and adults need only 1 dose their first time.

The flu vaccine is given each year beginning in October, but you can get it anytime during the late fall and winter months.

Not all brands of injected flu vaccine are approved for infants. Afluria’s approval for use in children under five was removed in 2010 because a higher than normal rate of febrile seizure reactions was found in children in New Zealand and Australia with its use during the 2010 flu season. Be aware that some doctors may not know about the age restrictions on some brands, so it’s important to make sure your child receives a brand approved for his or her age. People who are allergic to eggs should not get a flu vaccine, according to the product inserts.

In addition, the following people should not get the live-virus nasal spray vaccine:

  • Kids under age 17 who have a medical condition that requires them to take aspirin routinely. When aspirin is combined with the flu (even the live-virus vaccine in the nasal spray), a life-threatening reaction called Reye’s syndrome can result.
  • People with chronic lung, heart, or immune system disease. The killed injected vaccine is safer for them.
  • Children under five years of age with a history of recurrent wheezing. The live vaccine has the potential to trigger wheezing in such children.
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