Is it time to worry about bird flu?

The flu is a common infectious illness caused by a virus that results in symptoms like fever, body aches, and a cough. It is usually more severe than a common cold and often requires bed rest to recover.

Viruses are microscopic infectious agents that can only replicate inside the living cells of an organism. They are responsible for many diseases in humans, animals, and plants, and the term is also used for malicious computer programs.

To extend over a larger area or to a larger number of people. It can also refer to a soft food that is applied to bread or crackers.

The number equivalent to the product of a thousand and a thousand; 1,000,000. It is also used informally to mean a very large number or quantity.