Cow Pox pustules on a Cow's Udder
Both viruses and bacteria cause diseases in plants and animals. It’s important to note, though, the vast majority of bacteria are harmless to humans, and a great number of bacteria are essential to our survival. Viruses, bacteria, prions and fungus that cause disease are known as pathogens. Pathogens are simply infectious agents; as the word origin suggests in this case: “pathos” means suffering and “gen” means the generation of. A virus is an interesting entity that hovers on the cusp of being life. It is basic genetic material boiled down to the most essential elements: genes, protein and sometimes, a lipid outer shell, built using the host’s cellular material. That’s it. Bacteria are prokayotic cells, of which there are many, many varieties. Prokaryotes lack a nucleus and have very few (if any) membrane bound organelles (cellular organs wrapped in their own individual coating).
A virus cannot multiply on its own; it needs to be inside a cell in order to divide. Typically, a virus is proliferated in the following manner: first, it attaches to the outer shell of a cell and either through diffusion or chemical messenger channels, is absorbed. Next, the protein covering protecting the viral DNA or RNA (there are both DNA and RNA viruses) dissolves, releasing the virus’ genetic material. The plant, animal, or fungi cell then combines its own DNA with the viral DNA and begins making copies. Since the viral DNA is actually combined with the host’s DNA, any host cell division will also make a copy of the virus. Viruses can also proliferate by cellular lysis: the host cell completely fills up with copies of the virus, causing the cell to burst and spew out viruses which can then infect other cells in the body. The perfect parasite!
Now the biggest, medically relevant difference between viruses and bacteria is how they are treated when infecting a body. Antibiotics only treat bacterial infections; not viral ones; like the Common Cold or Influenza. Your body needs to just batten down the hatches and kill the viral invaders on its own. It has only been very recently that drugs have been developed to treat a virus once it has become symptomatic: Tamiflu and Relenza are but a few. The main defense against viruses is still vaccines: altered forms of the virus introduced to the body to create an immunity “memory”. Our body then recognizes subsequent exposures to the same virus and can mobilize an immune attack accordingly. The etching at the right is Cow Pox, the much less dangerous form of a similar strain called Small Pox. It was discovered that those who were exposed to Cow Pox, did not succumb to Small Pox as the Cow Pox created an immunity memory.
