Virus

Slovak term: Slovenský termín

1. A sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell (WHO 2009).
2. A minute organism not visible by light microscopy (Symons et al. 2000).
3. See also : Infectious disease.

Explanation

A virus is an obligate parasite dependent on nutrients inside cells for its metabolic and reproductive needs. It consist of a strand of either DNA or RNA, but not both, separated by a protein covering called a capsid (Symons etal. 2000).

Viruses consist of two or three parts : all viruses have genes made from either DNA or RNA (but not both), long molecules that carry genetic information; all have a protein coat called a capsid that protects these genes; and some have an envelope of fat that surrounds them when they are outside a cell. They are about 100 times smaller than bacteria (WHO 2009).

Example

A range of disease are caused by infections with viruses, ranging from influenza and measles to yellow fever, dengue and various forms of encephalitis (WHO 2009).

References

• Symons JM, Bradley LC and Cleveland TC (2000) The drinking water dictionary, American Water Works Association.
• WHO(2009) Health impact assessment glossary: E-learning modules.

Links

• WHO — The Health and Environment Lexicon