The flu is caused by two types of viruses in humans (influenza A and B). After infection, symptoms take between 1 to 3 days to show.
The flu is spread between people through droplets in the air.
Symptoms include: tiredness; fever; chills; headache; cough; sneezing and runny nose; poor appetite; and muscle aches.
Further health problems can develop in some people after infection with influenza including pneumonia, heart, blood system and liver complications, which can lead to death, especially in children and older people and those with pre-existing health conditions.
Flu Vaccine studies show very little benefit
Vaccines for preventing influenza in healthy adults.
Vaccines for preventing influenza in healthy children
Influenza vaccination for healthcare workers who care for people aged 60 or older living in long-term care institutions
Flu Shots May Not Protect the Elderly or the Very Young
Flu Vaccine for All: A Critical Look at the Evidence