We all live and prosper in a sea of viruses. Right now, as you are reading this article, viruses pulse through your bloodstream, intestines, lungs, and everywhere in your body. They’re on every surface in your house and floating in the air around you. You even have evidence of viruses in your DNA! They infect every living thing on earth, even things as small as bacteria and viruses themselves. So how is it that most of these viruses don’t impact our health in any negative way?
Many viruses pass through our digestive system. We often eat plants that are infected with viruses or have insect viruses on them, but it doesn’t matter because they have no impact on our health. Plant or insect viruses cannot cause infection in humans because they are specialized to infect plant or insect cells. Some viruses can be beneficial to their hosts, and even necessary for their survival. An example of a good virus occurs at the geothermal hot springs around Yellowstone National Park. The grasses that grow around hot springs must be able to withstand high temperatures (up to 130 ºF). In order to withstand these hot temperatures, the grasses require a fungus, which is infected by a virus. When these grasses grow without the virus-infected fungus, they do not survive at high temperatures. The mechanism for this process isn’t completely understood; however, the virus seemingly suppresses the stress response of the grass to high temperatures, allowing for their survival near geothermal hot springs.
So now that we know viruses aren’t always bad, what is a virus? Professor Vincent Racaniello of Columbia University’s Microbiology and Immunology department defines them as “an infectious, obligate intracellular parasite comprising genetic material surrounded by a protein coat or membrane.” Let’s unpack this definition. A virus is “infectious” because it enters the cells of living organisms. A virus on its own is not alive and cannot reproduce. “Obligate intracellular” refers to how viruses must infect the cells of living organisms in order to survive and reproduce. Viruses are “parasitic” because they cause some damage to cells, even if they don’t cause disease in the organism as a whole. Viruses have “genetic material,” referring to DNA or RNA, surrounded by a coat of proteins. Viruses replicate by inserting their DNA or RNA into the cells of other organisms, where the cell-machinery of the host can replicate the viral genetic material.
What about the viruses that are bad for humans? Disease-causing viruses are referred to as pathogenic. These viruses spread in the mucousy aerosol that leaves a person’s body when they cough or sneeze, or when you touch a surface that has particles of mucous from a sick person. Luckily, humans have a fantastic system in our body that removes pathogens without us even asking it to- the immune system! Young and healthy individuals are well-equipped with anti-viral cells to fight off infections. However, this can be problematic for the elderly and people with suppressed immune systems. So what can we do to stop the spread of pathogenic viruses to these people? Washing your hands can prevent infection because soap breaks down the protein coat on the virus, staying up to date on your vaccinations can give your immune system more tools to fight viruses, and staying home when you are sick to avoid spreading the virus to others. Although the majority of viruses have no impact on human health, it is important to stop the spread of viruses that can cause disease.
Meredith Grupe is a Naturalist at Walking Mountains Science Center who loves the Colorado Rockies. In her freetime you can find her hiking, skiing, singing and drawing.