Where Do New Viruses Come From?

If you’ve been watching the news you’ve probably heard of the new coronavirus which, starting in late 2019, began making people ill in China. International air travel has since allowed it to spread, person to person, to new countries.

As governments began to issue travel restrictions and even quarantines, speculations on the origin of the virus began to spread online. Some claim it might be a genetically engineered weapon, but extraordinary claims require extraordinary evidence. This claim seems highly unlikely.

Others suggest the virus may be an escaped lab specimen. This actually is possible, viruses have escaped from research labs in the past but as of the time this script was written, investigations into this idea have not reached any solid conclusions.

Could there be another, more natural explanation for the virus? Yes!

COVID-19, the new human infecting coronavirus, may have simply evolved from an older animal-infecting coronavirus.

To see how this could have happened, let’s first take a look at viruses in general.

Of all the things that can make you sick by infecting and reproducing inside you, viruses are among the smallest. If we resize this drawing to a more realistic scale, you see that hundreds of viruses can fit inside a single bacterial cell. That’s how small they are!

Thousands of different viral species have been studied and described so far, millions more likely exist. They come in many forms but all species consist of a small collection of genes – stretches of either DNA or RNA that carry information for making more copies of the virus – and those genes are enclosed in a protective coating of protein and sometimes a lipid membrane.

All known viruses are parasitic but most are not parasitic to humans. Instead, some only target plant cells, others only infect bacteria cells and so on.

A virus reproduces by getting its genes into a living cell. Different viruses do this in different ways but once inside, the cell acts as if the viral genes are its own genes. It begins reading them, and building copies of the virus instead of performing its normal tasks.

Some viruses are relatively gentle – they simply steal a small portion of a cell’s resources and then slip out fairly harmlessly. Others are absolutely brutal! After making as many copies of themselves as possible, they rip apart their host cell to escape and infect another.

Coronaviruses are a huge family of virus species that infect animal cells. Some infect chickens, others infect pigs, several infect humans but most of them are extremely mild – they simply give you the common cold.

Corona means crown and refers to the unusually large crown-like spikes sticking out of their membranes. These protein spikes are selectively sticky, sort of like velcro. They don’t attach to most objects but are extremely sticky when they bump into specific molecules found on the outsides of animal cells. Held firmly in place, the coronavirus waits until swallowed by the cell. It then begins to reproduce at the cells expense.

Different animal species have different types of molecules on the outsides of their cells. Because of this, bird infecting coronaviruses usually can’t infect humans. Their “velcro” doesn’t hold strong enough to our cells. Unfortunately, the natural process of evolution can sometimes help a virus overcome this problem.

When virus genes are being copied during reproduction, mutations can occur. These are either due to simple copying errors, or processes called reassortment and recombination. These happen when 2 or more viruses infect a single cell.

In most cases, mutations that change the shape of viral spikes render the virus useless – their velcro no longer sticks to any host cell. On rare occasions, however, a chance mutation will just happen to allow a virus to attach to a new host species. If that modified virus is then lucky enough to encounter that new host species, infection can occur. We call this a spillover infection. The virus spilled over into a new type of host.

Early on in a spillover event, the virus usually isn’t very good at infecting its new host. It’s velcro is not a perfect match, and many other challenges might slow the virus down. Often times, the mutations that let it infect the new host also make it worse at infecting its old host. Because of this, many spillover viruses go extinct after infecting just one or two people. However, if the virus can survive and reproduce just long enough, natural selection will promote any new mutations that help it better spread and reproduce within the new host population. Positive mutations accumulate over multiple generations, negative mutations are discarded until BAM! A new epidemic is being screamed about on the news.

Though it may seem to us that the new virus just popped into existence, scientists now know there is a long slow burn before each explosion.

Genetic evidence tells us that slowly evolving spillovers have been the cause of almost every major outbreak known in history.

In the early 2000s, a coronavirus that used to only infect bats appears to have spilled over into civets. There it mutated even further and spilled over into humans. We called it the SARS virus because it causes Severe Acute Respiratory Syndrome. It spread internationally from person to person and several scientists were also infected in the lab. By the time the virus was contained, over 8,000 people had been infected, over 700 died.

A coronavirus in camels also recently spilled over to humans causing even more deaths.

Coronaviruses are not the only types of animal viruses that can adapt to new hosts.

HIV spilled over from chimps, most likely when someone cut themselves while preparing chimp meat for dinner. The swine flu came partly from pigs, but we think it evolved through recombination with a type of bird flu. The 1918 Spanish flu – the big one that devastated populations around the world – may have spilled over from chickens.

While evidence is not yet conclusive, the new coronavirus might just be one more example of normal evolution. A similar virus has been known in bats and another similar virus was recently discovered in pangolins – these are endangered animals often used illegally for food, rituals, and alternative medicine in the region where COVID-19 first broke out.

There are serious people checking to make sure the virus did not come from a lab, either by accident or on purpose. Afterall, the technology to genetically modify a virus really does exist, but it’s important to understand that the normal process of descent with modification, acted upon by natural selection really does produce new viruses.

The chance of a virus evolving to successfully infect a new species is extremely low, but… There are over 7 and half billion people on this planet. Most of us interact with animals on a daily basis. We keep them as pets, we eat them as food.

This means that as unlikely as spillover infections might be, there are billions of opportunities for one to take hold, every single day.

Add this to the fact that the entire world is now connected through international flights and you realize that what happens in Vegas doesn’t really stay in Vegas, at least not the way it used to.

Luckily we have international groups like the World Health Organization and various Centers for Disease Control to help contain outbreaks when they happen. With international cooperation, we have prevented many catastrophes in the past, we will prevent many more in the future, so long as our species continues to work together.

So in summary, where do new viruses come from? In most cases, new viruses evolve from old viruses. Stopping the spread of new viruses requires international cooperation. For real time, accurate information on current risks and what you can do to stay safe, visit the world health organization website at WHO.int

I am Jon Perry and that is how new viruses evolve, Stated Clearly.