This introduction was originally published in Canadian Disasters, Scholastic Canada. Copyright René Schmidt 2013.      

Viruses and Bacteria

Viruses are as old as life itself. Not quite alive yet not quite dead, like seeds, these simple groups of proteins wait, for seconds or for centuries, for the perfect type of host cell to enter. Most viruses are harmless. They live on and in every sort of plant or animal.  

Some harmful viruses cause the common cold, chicken pox or cold sores. The virus uses the cell to make copies of itself and sometimes destroys the host cell as it leaves.  Copying, destroying, invading a new cell and copying again, within hours a single destructive virus can reproduce into millions, leaving destroyed tissue behind.  








Most viruses can only enter a host cell of only one type of living being, like the polio virus in humans. Others, like the rabies virus, can enter a wide range of hosts. Some viruses like the AIDS virus is passed through sexual contact, and others like the virus that caused SARS, began as harmless to animals but became deadly after entering human cells. 

Bacteria also co-exist with us.  The human body has ten times as many bacteria living on us and in us as the total number of cells in our body!  Some bacteria are useful, such as those that help to digest food. Bacteria are usually 100 times larger than viruses, and can usually be seen through a microscope.  Bacteria causing illnesses can enter our bodies through spoiled food, like salmonella bacteria, or through cuts or skin piercings, like staphylococcus. Bacteria can also be inhaled, like pneumonia or tuberculosis, or sexually transmitted like chlamydia.   

In the medical stories that follow the victims are everyday Canadians and the heroes are the medical professionals, nurses and doctors, researchers and technicians who spend hours treating the sick, identifying a virus or bacteria and tracking down the proper remedies or cures.  We are privileged to live in Canada. Our health care system, while not perfect, is one of the best in the world, making our country safer all the time.    

Copyright Rene Schmidt, 2013.