There are different types of influenza. There is the annual seasonal influenza and others, such as the H1N1 influenza, avian flu, and swine flu.
There are three separate types of viruses that affect humans:
- Type A: Type A influenzas affect both people and animals, such as birds. The animals help spread the virus, which can be very serious. The type A flus are the ones that cause most of the flu pandemics or epidemics. In 1918, the world was hit with the flu outbreak which killed millions of people. It was feared in 2009 that the H1N1 virus would have similar outcomes.
- Type B: Type B influenzas do not infect animals and do not cause epidemics or pandemics, but they still can cause serious harm.
- Type C: Type C influenzas are milder than either types A or B. They do not cause epidemics or pandemics and they only affect humans.
The viruses that cause influenza are not static, which means they do not stay the same. They can change and mutate, turning into new viruses. This is why if you catch the flu one year, you can catch it again the next – because the virus has changed enough from the year before that your body doesn’t recognize it.
The types of influenza, such as H1N1, are named by their make up. There are 16 subtypes of hemagglutinin (the “H”) and nine subtypes of neuraminidase (the “N”). These are proteins that help make up the virus. Therefore, the name of the virus is given by which humagglutinin and which neuraminidase are present.
The most commonly known influenza is the seasonal one. This is a different virus that moves around the world each year. The most recent statistics available for influenza are from the 2018/19 flu season. The CDC estimates that the seasonal flu killed an estimated 34,200 people during that season. Although this was down from the 61,000 flu-related deaths the year before, 34,200 people is just about twice the number who can fit in the United Center, where the NHL’s Chicago Blackhawks play. The number represents two full arenas of people.