Seasonal influenza, commonly called “the flu,” is caused by influenza viruses, which infect the respiratory tract (i.e., the nose, throat, lungs). Unlike many other viral respiratory infections, such as the common cold, the flu can cause severe illness and life-threatening complications in many people.
Some people, such as older people, young children, pregnant women, and people with certain health conditions, are at high risk for serious flu complications. The best way to prevent seasonal flu is by getting a flu vaccination each year.
Flu vaccines protect against the influenza viruses that research indicates will be most common during the upcoming season. Everyone 6 months and older should get vaccinated against the flu every year. Get vaccinated soon after vaccine becomes available in your community, if possible by October. Immunity sets in about two weeks after vaccination.
Fever, chills, fatigue, body aches, sore throat, and headache are common symptoms of flu. Not everyone with flu will have a fever. The flu can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. The flu usually comes on suddenly.
In the United States, flu season occurs in the fall and winter. The peak of flu season has occurred anywhere from late November through March.
The main way that influenza viruses are thought to spread is from person to person in respiratory droplets of coughs and sneezes.
People with flu can spread it to others up to about 6 feet away. Most experts think that flu viruses are spread mainly by droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth or nose.
To avoid this, people should stay away from sick people and stay home if sick. It also is important to wash hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub. Linens, eating utensils, and dishes belonging to those who are sick should not be shared without washing thoroughly first. Eating utensils can be washed either in a dishwasher or by hand with water and soap and do not need to be cleaned separately. Further, frequently touched surfaces should be cleaned and disinfected at home, work and school, especially if someone is ill.
Most healthy adults may be able to infect other people beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. Children may pass the virus for longer than 7 days. Symptoms start 1 to 4 days after the virus enters the body. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Some people can be infected with the flu virus but have no symptoms. During this time, those persons may still spread the virus to others.
Several studies conducted over different flu seasons and involving different influenza viruses and types of flu vaccine have shown that a person’s protective antibody against influenza viruses declines over the course of a year after vaccination and infection, particularly in the elderly. So a flu shot given during one season, or an infection acquired during one season, may not provide adequate protection through later seasons. So, for optimal protection against influenza, annual vaccination is recommended regardless of past vaccination status or flu infection.
Thanks to cdc.gov for this information! To learn more about the flu please visit the CDC's flu information page by clicking here.
image courtesy of chidrenshospital.org