How do People Get the Flu?

The "Stomach Flu" The term "stomach flu" is actually a misnomer. Vomiting, diarrhea and stomach aches can be caused by a virus, but they are rarely related to the flu. The flu is a respiratory illness, not a gastrointestinal one.

Flu season in North America runs from November through March, but dates can vary from year to year. January and February tend to be the most active flu months.

During flu season, people begin coming down with the illness, and they quickly spread it to friends, family and coworkers. Schools are particularly notorious for spreading the flu, because students are in such close quarters. And when a child picks up the virus, he or she often brings it home and shares it with the rest of the family. The National Institute of Allergy and Infectious Diseases estimates that one out of every three families of school-aged children is infected with the flu each year.

How is the flu spread?
The flu is highly contagious. It is spread primarily by coughing and sneezing (which people who have the flu tend to do a lot of). Let's say you have the flu virus. Every time you cough or sneeze, you release tiny droplets of fluid into the air. Those tiny droplets can fly pretty far -- up to 3 feet (about 1 meter). If some of those droplets land on the nose or mouth of a person standing nearby, that person is likely to get as sick as you are, usually within one to four days. You can also spread the virus if you touch something (like a doorknob or table) after you've sneezed or coughed into your hand, and then other people come along and touch the same doorknob or table and put their hand on their nose or mouth.

If you have the flu, you're not just contagious when you have symptoms. You can pass along the virus one day before you start sniffling and sneezing, and you can keep passing it along for seven days after you start sniffling and sneezing. Children can be contagious even beyond the seven days.

The 1918 Flu Pandemic Normally, the flu only spreads to people in the country in which it originated. But sometimes, the illness can travel and infect people around the world. This rampant spread is called a pandemic. The worst flu pandemic in history struck in 1918. Between 1918 and 1919, the pandemic killed more than 500,000 people in the United States and more than 20 million people worldwide. More lives were lost in this flu pandemic than in all of the 20th century wars combined. Photo courtesy U.S. Navy Poster issued by the U.S. Treasury Department during the 1918 flu pandemic