What is a Virus?

There are some things that I just think are cool. One of my interests (perhaps not shared by many) is in viruses. Frankly, I think ‘bugs and germs’ are fascinating. So, allow me to share. Maybe you’ll start to believe they are, too.

What is a virus? 

A virus is a type of infectious agent. Roughly speaking, there are five types of infectious agents, but most people are aware of two of them: bacteria and viruses. These are very different.

Bacteria

Bacteria cause diseases such as strep throat, some pneumonias, skin infections, and even the plague. Diseases caused by the different types of bacteria can usually be treated with antibiotics. These are substances that attack the infectious agent, but not the host (you or me). In addition, because bacteria are living beings, they can usually be killed by high concentrations of alcohol and other disinfectants.

Viruses

Viruses are infectious agents that are on the border between being alive and not. They don’t eat, move, or breathe. They are MUCH smaller than bacteria. Viruses were discovered when a scientist noticed that some infectious agents pass through membranes that filter out bacteria.

Even though viruses are not alive in the traditional sense, they can reproduce — with help. Viruses are obligate intracellular parasites; they hijack cells. The infected cells then make viruses, instead of carrying on the normal processes of life. Viruses can’t grow on nonliving surfaces, but they can exist there for extended periods of time.

Can we kill viruses?

Inactivation can Happen Outside the Host.

A virus outside the host (you or me) can be inactivated by heat, bleach, formaldehyde, and the like. Some viruses are covered by a membrane, and those may be inactivated by lengthy exposure to high concentrations of alcohol, as well. Antibiotics don’t work on viruses. A quick spritz of hand sanitizer doesn’t inactivate most viruses.

No Inactivation Inside the Host

A virus that has infected the host is difficult to inactivate, because it’s inside cells. The only way to inactivate them is to destroy the hijacked cells. That’s why you get a sore throat with a cold—your body is blowing up your throat cells to stop them from making viruses.

Viral Toolbags

Some types of viruses carry tools, known as enzymes, which the cell needs to make more viruses. Antiviral medications target these tools. The medicines don’t harm our cells, because we don’t make or need those enzymes. The tools are often specific to the type of virus, so an antiviral medication for one virus may not be efficacious against another. Viruses quickly become resistant to antiviral agents, just like bacteria can become resistant to antibiotics.

How do viruses spread?

Since viruses aren’t alive, they can’t move. Rather, the host spreads them in several ways: via respiratory droplets, via the fecal-oral route, by direct contact, and via blood and other fluids.

We all know that colds are spread when infected people cough and sneeze, and we either breathe in the airborne virus or touch an infected surface and pick our nose.

The 24-hour tummy bug is spread when one person ingests another person’s fecal matter, which, amazingly, can get everywhere. Seriously. TMI?

Bodily fluids transmit HIV.

And, of course, COVID is mainly spread through the respiratory route.

Where did COVID-19 come from?

Coronaviruses have been around for a long time. In fact, 20% of our colds are caused by a type of Coronavirus. But this particular virus, COVID-19, probably originated in animals, which is precisely what makes it more serious in people.

A successful pathogen (one that gets passed on) doesn’t make its host very sick. If it did, the host wouldn’t be able to pass on the virus, because they would be bed-bound or dead. COVID-19 doesn’t make its animal host very ill.

Initially, because the virus had not yet adapted to humans, it caused severe illness. But over time, the milder and more contagious subtypes of COVID-19 became more prevalent, since the lethal viruses aren’t spread as effectively. Why not? Because a virus needs a living host to multiply! Of course, it doesn’t hurt that most of us now have some immunity, as well.