Hope Cortner, age 12, of Watertown, N.Y., for her question:
JUST WHAT IS A VIRUS?
A virus is a microscopic organism that lives in a cell of another living thing. Viruses are the smallest and simplest form of life and are a major cause of disease.
Viruses are so primitive that many scientists consider them to be both living and nonliving things. By itself, a virus is a lifeless particle that cannot reproduce. But inside a living cell, a virus becomes an active organism that can multiply hundreds of times.
Unlike other organisms, viruses are not made up of cells and therefore lack some of the substances needed to live on their own. To obtain these substances, a virus enters a cell of another living thing where it can then live and reproduce.
Most viruses reproduce in specific cells of certain organisms. As an example, viruses that cause colds reproduce in cells of the human respiratory tract. Viruses cannot live outside their particular cells. They must be carried into the organism by air currents or some other means and then transported by body fluids to the cells.
Virus diseases in human beings include chicken pox, colds, cold sores, hepatitis, influenza, measles, mumps, poliomyelitis, rabies, smallpox and yellow fever.
Viruses are shaped like rods or spheres and range in size from about 0.01 to 0.3 micron. It would take 25,400 microns side by side to measure one inch.
The study of viruses started in 1889 when a Dutch botanist by the name of Martinus Beijerinck realized that something smaller than bacteria could cause disease. He named this particle a virus, a Latin word meaning “poison.”
In 1935 an American biochemist named Wendell Stanley showed that viruses contain protein and can be crystallized. This research and many other studies eventually led to the development, during the 1950s, of vaccines for measles, poliomyelitis and other diseases.
Since the 19609, experiments with cancer viruses has become an important research project.
The body protects itself from viruses and other harmful substances by several methods, all of which together are called the immunity system. As an example, white blood cells called lymphocytes provide protection in two ways.
Some lymphocytes produce substances called antibodies which cover a virus, protein coat and prevent the virus from attaching itself to the receptors of a cell. Other lymphocytes destroy cells that have been infected by viruses and thus kill the viruses before they can reproduce.
Lymphocytes do not start to produce antibodies until several days after a virus has entered the body. However, the body has additional methods of fighting virus infection.
The body produces a high fever to combat such virus diseases as chicken pox and measles. The high fever limits the ability of the viruses to reproduce.
To fight colds, the body forms large amounts of mucus in the nose and throat. The mucus traps many cold virusus which are expelled from the body by sneezing, coughing and blowing ones nose.