Virus

Virus A virus (from the Latin virus meaning toxin or poison) is an infectious agent that is unable to grow or reproduce outside a host cell.

Reproduction Attaches itself to a cell Inserts genetic material Genetic material take over cells function Cell begins to make copies of the virus The viruses seek out a new cell

Spread of Viruses Viruses spread in many ways; different species of virus use different methods. plant viruses are often transmitted from plant to plant by insects that feed on sap. while animal viruses can be carried by blood-sucking insects. Influenza viruses are spread by coughing and sneezing. others are transmitted when they contaminate hands, food or water. HIV is one of several viruses that are transmitted through body fluids.

Description of Viruses Viruses are about 100 times smaller than bacteria. Most viruses are unable to be seen with a light microscope To increase the contrast between viruses and the background, electron-dense "stains" are used.

Human Resistance The body's first line of defense against viruses is the immune system. When the immune system encounters a virus, it produces specific antibodies which bind to the virus and neutralize it.

Preventing Viral infections Vaccination is a cheap and effective way of preventing infections by viruses. Their use has resulted in a dramatic decline in illness and death associated with viral infections such as polio, measles, mumps and rubella. Live vaccines contain weakened forms of the virus that causes the disease.

Plants There are many types of plant virus, but often they only cause a loss of yield Plant viruses are often spread from plant to plant by organisms, normally insects, fungi, and worms.

Edward Jenner