Article: What exactly is a virus?

At the time of this post, the world is hearing a lot about viruses due to the Covid-19 (a.k.a. “Coronavirus”) pandemic. Fortunately, the trend of doctors prescribing antibiotic medication to treat viruses seems to have subsided. However, many people only grasp the “tiny bugs too small to see must be washed away so they don’t make us sick” explanation. While it’s adequate for children, few adults have a cursory understanding of basic microbiology. Their ability to sift through the abundance of jargon that’s so flippantly tossed around will determine how they approach the prevention and treatment of illness.

There are distinct differences in types of microscopic organisms, called “microbes,” some of which are harmless; it’s the disease-causing ones we commonly call “germs.” Bacteria are single-celled organisms. Some, such as intestinal bacteria are helpful for digesting food; some produce toxins powerful enough to damage cells or even invade tissue, which cause sickness, such as Strep throat, Tuberculosis and urinary tract infections. Viruses are capsules that contain genetic material. Since they’re much smaller than cells, they hijack the machinery that makes their host cells work (most eventually destroy them). Examples of these are the common cold, Influenza, Herpes/ Chickenpox/ Shingles, Measles, AIDS, Ebola and Rabies. Fungi, which are classified in their own kingdom can be single or multi-celled. Their reproduction more closely resembles that of animals than plants (seeds contain a full number of chromosomes whereas spores contain only half), especially mold and mushrooms, which can be harmless or poisonous; the wall that surrounds their cells differs from that of all other living organisms. Protozoans are single-celled organisms that hunt and gather other microbes for food as animals do. They live in food, water, soil and insects, which is how they come to enter a host. Many cause diseases, such as Malaria and Giardia. Helminths (Greek for “worms”) are parasites, who live off their host’s nutrients. The most common examples are tapeworms and roundworms.

For our purposes, let’s focus on viruses, which are so tiny they can only be seen with a high-powered microscope. Their size varies, the largest being up to 1,500 nanometers. Compare that to the width of a human hair, which measures 20,000 nanometers! “Getting sick” happens when your body is exposed to a pathogen (disease-causing microbe). When the microbe enters your body, one of your cells becomes the pathogen’s host. Once inside, the microbe multiplies in the same way animals/ insects enter your home and breed causing an “infestation”. During the incubation period, most people don’t realize there are germs reproducing inside them. When the microbes start causing damage to– and in some cases destroying– the cells they’ve invaded, signs of infection appear, i.e. you can at least feel, if not see, the damage. (Symptoms can include headache, body aches, fever, chills, cough, nausea, vomiting.)

The exact structure (shape) of each viral strain depends upon which species is its host but a typical virus is basically a set of genetic material (“genome”) surrounded by a shield of proteins. This protective coat/ envelope protects the virus between hosts; it opens as it punctures through a cell membrane (outer wall) to deposit a chain of nucleic acids (DNA/ RNA) into that cell. The coat is then discarded and the virus’ genome replicates using the host’s own cellular machinery, i.e. it reproduces to spread the virus. Fortunately, the Immune System has pattern recognition receptors– proteins capable of recognizing molecules frequently found in pathogens. The bloodstream can send the appropriate antibodies, assuming it’s had the time and ability to generate them.

To help stop the spread of germs and to prevent yourself– and those you love– from getting sick, it’s crucial to realize there are differences in kinds of pathogens. A bacterium is not a virus is not a fungi is not a protozoan is not a helminth. An effective treatment for bacteria will not work on a virus, just as a substance that kills influenza won’t kill  mold. When you know what kind of germs you’re dealing with, you can select the most appropriate course of action to take against them.


etymology online: virus      biology dictionary: virus      Mayo Clinic: germs

Basic Biology: fungi      function of seeds & spores in plants

how pathogens cause disease      Medical Microbiology: viral pathogenesis

MIT: viruses      MIT News: biochemists discover mechanism that helps flu viruses evolve

the biology of Influenza Virus

biological physics: molecular machines      Harvard Med: cell biology

pattern recognition receptors and host cell death molecular machinery

viral hijacking of cellular metabolism

the role of cellular adhesion molecules in virus attachment & entry

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