What is a virus?

A virus is a tiny germ that can make animals and plants sick. They are too small to be seen with a microscope, an electron microscope is needed to see them. Viruses only have DNA or RNA (genetic material) and a simple shell. They cannot grow or divide by themselves. They must take over a cell, and force the cell to create copies of the virus. The cell often dies in the process. The new viral copies then invade other cells. When enough cells are killed, you become sick. The picture from an electron microscope below shows multiple viruses near a human cell.

 

Multiple viruses near a cell. (Source: Jon Charlesworth; Mayo Clinic).

Will penicillin prevent a viral infection?

No! Penicillin only kills some bacteria. Bacteria are single cell organisms which are too small to be seen without a microscope. There are thousands of different kinds of bacteria and they are everywhere. Most bacteria are not harmful, in fact some are necessary for our health. However, some can make us sick such as:

• Streptococcus pyogenes ( strep throat)
• Staphylococcus aureus (skin infections and food poisoning)
• Mycobacteria tuberculosis (tuberculosis)
• Salmonella typhi (typhoid fever)

There are only a few drugs currently available that have any effect at all on viruses and they are not nearly as effective as bacterial antibiotics.

How many viruses are in my body compared to bacteria?

To answer this question, we turn to Leo Grady from the Laboratories for Viral Diseases/Zoonotic Diseases, Wadsworth Center, New York State Dept. of Health. To see his expert response, click here!