Is it time to worry about bird flu?

A vertical shaft or chimney-like opening in the roof of a cave that leads upwards. These features are often formed by the chemical dissolution of limestone by water or by the structural collapse of a cave ceiling.

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.

Living beings belonging to the species Homo sapiens, distinguished by their ability to think, speak, and create complex societies. This term refers to people collectively as a biological or philosophical group.