Tiny viruses are having an enormous effect on our lives right now, from the usual colds and flu to the pandemic of the novel coronavirus, COVID-19.
Possibly the supreme marauder in nature, viruses infect all known forms of life, animals, plants, and fungi -- even bacteria.
Are viruses themselves alive? That’s debatable. Viruses could be thought of as life stripped down to its barest, most essential element: reproduction.
Viruses do not take in nutrients or pass waste; their only structures and processes are those directly related to holding their genetic material and injecting it into a suitable host. Each virus particle, called a “virion,” is composed of only a handful of parts: genetic material (either DNA or RNA), a protein coat around the genetic material, (usually) an attachment location or mechanism, and (sometimes) an encompassing envelope. That’s it.
The virion is totally inert until it encounters an appropriate cell membrane -- there’s no metabolism, no growth, no movement, only waiting. Each kind of virus is limited to infecting a small number of hosts, in some cases, infecting only certain strains of a single species.
At that encounter, the virion attaches to the host cell then injects its genetic material inside. Usually, the genetic material hijacks the cell's processes and directs it to make several dozen copies of the viral genetic material and other components that make a virion. The components then assemble into a number of new virions and burst out of the cell to disperse, usually killing the host cell.
The illness we feel with a viral infection, such as influenza, is a combination of the virus killing its host cells and our bodies' immune response revved up to high gear.
Sometimes, particularly with viruses that attack bacteria, the genetic material is incorporated into the host cell. In those cases, the infected host continues to live and reproduce, passing on the virus material to its own offspring. The viral genetic material inside a host may be forever incorporated in the genetic material of the host. Your DNA, for example, is up to 8% viral DNA.
Occasionally the virus' meddling moves material between bacteria. This mixing can serve the same function as sexual reproduction does in more complicated organisms, increasing the genetic diversity of the bacterial population.
Sometimes the viral DNA/RNA affects the way the biochemistry of the host works. For example, apparently the bacteria that cause botulism, diphtheria, and scarlet fever cause those diseases only when they harbor the genetic material of certain viruses. Too, this effect was likely the cause of seastar wasting disease that has decimated our starfish populations.
For most of us, though, having a lot of human-targeting viruses drifting through our bodies means illness.
Viruses' protein coats have varying durability, causing some to become unable to reproduce in fairly short order if exposed to a foreign environment. Other viruses can remain virulent under a wide range of conditions for great lengths of time.
Although a few chemicals can disable viruses, antibiotics have no effect on these ultimate parasites. What can control potentially dangerous viruses in multi-cellular animals like us is alerting the body’s natural antibody system by vaccinating with dead or disabled viruses or virus parts. The smallpox vaccine eliminated that deadly disease about 1980, and the vaccine for measles, developed in 1960s, is estimated by Merck & Co. to save up to a million lives a year worldwide. Such vaccines take some time to develop, however, and according to the US Centers for Disease Control and Prevention (CDC), a vaccine for COVID-19 won’t be available for at least a year.
Why are we encouraged to get a flu vaccine every year? Viruses are so marvelously good at mutating that there’s an uncountable variety of them and new ones are evolving constantly. (The annual flu shot vaccinates against the ones expected to be most common and most virulent.)
Sometimes a virus in other animals mutates enough to infect humans and cause disease. It is believed that one of the rhinoviruses that causes human colds was originally a virus in camels, and measles may have been a cattle illness that “jumped” to humans about 1,000 years ago. Although we don’t yet know for sure, preliminary analysis of the RNA of the COVID-19 shows that it may have originally been a virus that used bats, but mutated to use pangolins, then mutated again to use humans.
Tiny viruses are better adapted to passing on genetic material than any living thing. That’s not going to change, so we’re going to have to adapt our behavior if we want to control their effect on us.
Now, go wash your hands.
For information on how you can arrange an exploration of our fascinating natural history, contact Marty at 541/267-4027, email@example.com, or www.facebook.com/wavecrestdiscoveries. Questions and comments about local natural history are welcome.