Influenza or “flu” is a major cause of seasonal illness and death worldwide. It causes approximately 3 to 5 million cases of severe illness and up to 650,000 deaths worldwide every year.1
Influenza A and influenza B are the two main types of flu viruses that make people sick. There are many different strains of influenza A and B, and new strains are always evolving.
Flu is considered a seasonal illness because most cases occur during the fall and winter seasons. Since flu strains can change from one season to the next, flu vaccines are updated each year to closely match the flu strains that are circulating. Getting your annual flu shot is an important way to protect yourself and others from serious illness.