Let's talk infectious diseases, the reason for vaccines: ᴵⁿᶠˡᵘᵉⁿᶻᵃ

There are four types of influenza viruses: A, B, C and D. Human influenza A and B viruses cause seasonal epidemics of disease (known as the flu season) almost every winter in the United States. Influenza A viruses are the only influenza viruses known to cause flu pandemics, i.e., global epidemics of flu disease. A pandemic can occur when a new and very different influenza A virus emerges that both infects people and has the ability to spread efficiently between people. Influenza type C infections generally cause mild illness and are not thought to cause human flu epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

Influenza A viruses are found in humans and in many different animals, including ducks, chickens, pigs, whales, horses, seals, and cats. Influenza B viruses circulate widely only among humans.

The influenza virus infects the nose, lungs, and throat. It spreads when an infected person coughs, sneezes, or talks in the presence of other people. Droplets containing the virus may come into contact with a person via their mouth, nose, or eyes, and then cause infection. According to the CDC, the best evidence is that influenza is usually spread by large droplet transmission, which can occur within six feet of an individual.

Touching a surface and then touching your mouth, nose, or eyes may also transmit the flu. The virus may end up on a surface due to respiratory droplets or hands contaminated by respiratory secretions. Social interactions such as shaking hands can transmit the virus in this way as well.

Common symptoms include the following:

▪️ Fever and chills

▪️ Exhaustion

▪️ Aches and Pains

▪️ Coughing

▪️ Headache

▪️ Congestion

Vomiting and diarrhea are not common flu symptoms for most people, but some do experience them. Children are more likely to have vomiting and diarrhea with influenza than adults.

If vomiting and diarrhea are your primary and most significant symptoms, you probably have a stomach bug (sometimes referred to as the stomach flu, though it is not influenza) instead.

In the deadly Spanish influenza pandemic of 1918-19, investigators attempted to develop vaccines to prevent influenza, though they had not yet correctly identified the causative pathogen. These vaccines would certainly not have prevented influenza infection--as we know now, the pandemic was caused by a new strain of the influenza A virus. Influenza viruses would not be isolated and identified until the 1930s, and the first commercial influenza vaccines were not licensed in the United States until the 1940s.

By the end of 1940 researchers had figured out that there were several different influenza viruses so vaccine development had to take that discovery into consideration. In 1945, the first influenza vaccine was approved for military use in the United States. It was approved the next year for civilian use. Influenza vaccine development was a high priority for the U.S. military after the deaths of approximately 1 in every 67 soldiers from influenza during the 1918-1919 pandemic.

As new strains were discovered, vaccines were altered and developed to provide protection against the worst strains. The seasonal flu vaccine protects against the influenza viruses that research indicates will be most common during the upcoming season.

Every flu season is different, and influenza infection can affect people differently, but millions of people get flu every year, hundreds of thousands of people are hospitalized and thousands to tens of thousands of people die from flu-related causes every year. An annual seasonal flu vaccine is the best way to help protect against flu.

{You can find all the sources I used by clicking here.}