Influenza viruses cause the flu, a contagious respiratory illness that infects the nose, throat, and sometimes the lungs. The CDC recommends annual influenza (flu) vaccinations as long as flu activity is ongoing.
* not everyone who gets the influenza (flu) virus will have a fever.
There are two main types of influenza (flu) viruses: types A and B. The influenza A and B viruses that routinely spread in people (human influenza viruses) are responsible for seasonal flu epidemics each year.
According to the CDC, children and people of 65+ years are most likely to get sick from influenza (flu).
According to the CDC, the effectiveness of influenza vaccination varies depending on several factors, such as the age and health of the recipient.