2. Influenza
Influenza, usually known as the flu, is a serious illness that affects the respiratory system and is brought on by a variety of influenza viruses.
Although there may have been influenza outbreaks as far back as 6,000 BC, the earliest instance of an epidemic of the respiratory disease we now know as influenza was documented in writing for the first time in 1510.
While some varieties of influenza are caused by humans, influenza pandemics often occur when a novel strain of the virus is transferred from one animal species to humans, particularly an animal that we eat (like pigs, chickens, or ducks).
The flu’s mild to severe symptoms typically include fever, runny nose, sore throat, muscle aches, headaches, coughing, and fatigue.
