What is flu? The essential facts about the disease formally known as influenza

The northern hemisphere’s flu season is upon us, the time of year when, the temperature having dropped, cases of influenza virus infections peak.

There have been many famous influenza pandemics throughout history, such as the Spanish flu of 1918, which killed between 40 and 50 million people; the Asian flu outbreak which lasted two years from 1956 and killed about 2 million; and the Hong Kong flu of 1968-69 which led to approximately 1 million deaths worldwide.

But what exactly is the disease, is it always that serious, and should you be worried?

What is flu?

Influenza – so named because in the past people thought that those who caught it were under the “influence” of an unlucky pattern of the stars. Today, though, we know it’s caused by a virus.

Different kinds of flu viruses affect different animals, including humans. There are three main forms that infect humans: Type A, Type B and Type C. The forms of the virus change each year, so there is always some or other type of flu going around.

How it spreads

The flu virus, like many others, is spread though contact with the virus. When someone who is infected coughs or sneezes, the virus is sprayed, almost like a deodorant spray, and hangs around in the air that others breathe in.