Frequently Asked Questions
When does the flu activity begin and when does it peak?
The flu activity varies from season to season and is very unpredictable. The peak of flu activity usually occurs in the U.S. in January or February. However, seasonal flu activity can occur as late as May.
How effective is the flu vaccine?
The effectiveness of the vaccine varies due to the level of the match between the viruses in the vaccine and flu viruses that are circulating in the community. If these are closely matched, vaccine effectiveness would be higher. If they are not closely matched, vaccine effectiveness can be reduced. Currently, the effectiveness of vaccine falls between 70% and 90% among healthy adults.
How many people get sick or die from the flu every year?
Overall, 5% to 20% of U.S. residents get the flu and more than 200,000 people are hospitalized for the flu-related complications each year. Flu-associated deaths also range from a low of about 3,000 to a high of about 49,000 people every year.
Is the "stomach flu" really the flu?
Many people use the term "stomach flu" to describe illnesses with nausea, vomiting or diarrhea. These symptoms can be caused by many different viruses, bacteria or even parasites, and they can sometimes be related to the flu, particularly in children. However, these problems are rarely the main symptoms of influenza. The flu is dominantly a respiratory disease and not a stomach or intestinal disease.
What is the difference between a "cold" and the "flu"?
The flu and the common cold are both respiratory illnesses but they are caused by different viruses. Because these two types of illnesses have similar flu-like symptoms, it can be difficult to tell the difference between them based on symptoms alone. In general, the flu is worse than the common cold, and symptoms such as fever, body aches, extreme tiredness, and dry cough are more common and intense. Colds are usually milder than the flu. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations.
How can you tell the difference between a cold and the flu?
Because colds and flu have similar symptoms, it can be difficult (or even impossible) to tell the difference between them based on symptoms alone. Special tests that usually must be done within the first few days of illness can be carried out, when needed to tell if a person has the flu.