What is influenza?

Influenza—the “flu”— is a common infection of the lungs and breathing passages, as well as other parts of the body. It affects millions of people, most often the young and old, in late fall, winter, or early spring. Influenza can be serious. Despite an increase in vaccinations in recent years, deaths due to flu complications have increased steadily over the past 20 years, especially among the elderly.

For healthy children and adults, influenza is moderately severe. Most people are back on their feet within a week. For elderly people, newborn babies, and people with certain chronic illnesses, however, flu can be very severe and lead to life-threatening complications. Most of these complications are bacterial infections because the body can be so weakened by influenza that its defenses against bacteria are low. Bacterial pneumonia is the most common serious complication of influenza. Dehydration, or loss of body fluids, can also be dangerous. Chronic medical conditions like congestive heart failure, asthma, or diabetes can become far worse. Sinuses and inner ears can become inflamed and painful. The elderly and persons of any age with chronic medical conditions are at highest risk for these serious complications of flu.

Flu is easy to catch, but can be avoided or minimized with a vaccine, or “flu shot.” Flu outbreaks usually begin suddenly and occur mainly in the late fall and winter. The disease spreads through communities creating an epidemic (the rapid spreading of a disease to many people). During the epidemic, the number of cases peaks in about 3 weeks and lessens after another 3 or 4 weeks. Half of the population of a community may be affected. Because schools are a typical place for flu viruses to spread, families with school-age children have more infections than other families.

To learn more:

Is It a Cold or the Flu?
(National Institute of Allergy and Infectious Diseases)
This article provides easy to understand information about the flu. It is a PDF handout that lists the differences between a cold and the flu.
https://www.niaid.nih.gov/sites/default/files/documents/sick_0.pdf
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Seasonal Influenza (the Flu): Questions & Answers
(Centers for Disease Control and Prevention (CDC))
Basic questions about influenza (the flu) including types of viruses, prevention, and what to do if you get sick.
https://www.cdc.gov/flu/faq/index.htm
Key Facts About Seasonal Influenza
(Centers for Disease Control and Prevention (CDC))
This fact sheet gives a good basic description of the flu, its symptoms and how to prevent it.
https://www.cdc.gov/flu/keyfacts.htm

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Last Modified: Monday December 19, 2016 10:17 AM