It’s impossible to accurately determine the true number of influenza infections, as many infections are not reported to healthcare institutions.
In the United States, an estimated 5% to 20% of the population are annually infected with influenza viruses, which translates to 50 million cases.
Worldwide, between 3 and 5 million cases of severe illness occurs, with an estimated 250,000 to 500,000 influenza-related deaths.
About 21% of people living in the same house as an infected child or adult will contract flu, according to American research.
Reviewed by Cape Town-based general practitioner, Dr Dalia Hack. March 2019.