What is a pandemic?
A pandemic is the worldwide spread of a new disease. It’s important to note that the term pandemic refers to the geographic spread of a disease and not necessarily the severity of the disease.
An influenza pandemic occurs when a new influenza virus emerges and spreads around the world, and most people do not have immunity. Viruses that have caused past influenza pandemics typically originated from animal influenza viruses.
Some aspects of influenza pandemics can appear similar to seasonal influenza while other characteristics may be quite different. For example, both seasonal and pandemic influenza can cause infections in all age groups, and most cases will result in self-limited illness in which the person recovers fully without treatment or hospitalization. However, typical seasonal influenza causes most of its deaths among the elderly while other severe cases occur most commonly in people with a variety of medical conditions.
By contrast, the 2009 H1N1 (swine flu) pandemic caused most of its severe or fatal disease in younger people, both those with chronic conditions as well as healthy persons, and caused many more cases of viral pneumonia than is normally seen with seasonal influenza.
For both seasonal and pandemic influenza, the total number of people who get severely ill can vary. However, the impact or severity tends to be higher in pandemics in part because of the much larger number of people in the population who lack pre-existing immunity to the new virus. When a large portion of the population is infected, even if the proportion of those infected that go on to develop severe disease is small, the total number of severe cases can be quite large.
When is flu season?
Influenza activity usually lasts from October to May in the United States.
What can I do to stay well?
- Get an annual flu vaccine.
- Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
- Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
- Try to avoid close contact with sick people.
- While sick, limit contact with others as much as possible to keep from infecting them.
CDC Influenza Vaccine Information
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