This is a specific infection with one of the Influenza A, B or rarely, C, viruses. Influenza A, and to a lesser extent, B, are circulating all year round and have the ability to modify themselves frequently.


Infection is characterised by rapid onset of high fever and exhaustion and is followed by a cough and lower respiratory symptoms. Pneumonia may occur as a complication of influenza.


Flu vaccines become available each year prior to the flu season. The composition of the vaccine is reviewed each year to best match the strains of virus likely to be circulating in the community.

In 2015, a quadrivalent (four strain) vaccine became available. This contains extra cover against type influenza B. Immunity from flu vaccination wanes after six to twelve months, so it is important to boost immunity with a flu shot each year.

Ensure you have had an annual flu vaccination.