The Probert Encyclopaedia of Medicine

FLU

Flu is a term used today to describe a number of different viral infections that affect either the respiratory system or the stomach. Originally, the word 'flu' described a single collection of viral infections - influenza, and the term flu is still popularly used for influenza. The two most common types of viruses that cause flu, out of more than a hundred that have been identified, are known as Influenza A and Influenza B.
Flu symptoms appear in full force within a few days of the virus entering the system. Common complaints are fever, chills and shaking, headache, muscle aches, fatigue, and loss of appetite.
Research Flu