So there are 7 known strains of coronavirus that are known to infect humans: 4 that cause the common cold (229E, NL63, OC43 and HKU1), and 3 that have been known to cause acute respiratory infection (SARS, MERS and now COVID-19). They're all beta-coronaviruses except for 229E and NL63.

I can't help but notice the latter 3, which also happen to be the most serious, have all emerged very recently and within less than a decade apart from one another. I tried to find out how long the common cold strains have been around for, but can't find too much information on that (I found one article from science daily that says the common cold could have originated in birds around 200 years ago, but that's about it).

Does anyone have more information on this? Is the fact that SARS, MERS and COVID-19 emerged so close to one another a trend or just a coincidence? Are there any notable scientists who've noticed this and have an explanation as to why?

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    – tyersome
    Sep 3, 2020 at 18:14
  • $\begingroup$ Thanks for your response! I just graduated from undergraduate school so my biology skills aren't incredible yet so forgive me if my question seems vague and non-specific. I kind of just dumped whatever information I knew in the description. So the purpose of the question was just to figure out if there was a reason why coronavirus diseases specifically keep popping up. The reason why I mentioned the common cold strains was because I was wondering if there's evidence that they emerged in the human population recently, too. $\endgroup$
    – Andrew
    Sep 4, 2020 at 0:15

1 Answer 1


It is not a coincidence, but it doesn't have to do with sudden evolutionary changes, rather with human behavior.

The three viruses you mention are zoonotic — they can infect different species, including humans.

Increased development of formerly untouched lands is bringing people into contact with animals (and existing, but formerly unknown zoonotic pathogens) in greater numbers.

Humans bring the virus back to concentrated human populations — cities, say — either being infected themselves, or bringing back infected animals for consumption. This increases the opportunities for further spread.

With the help of global leadership that is corrupt, incompetent, or antiscience, the multiplier effect of repeated infections in cities turns a small pool of cases into a pandemic. Rinse and repeat.

The risk of emerging infectious diseases such as COVID-19 from animals is on the rise, in large part because of our environmental footprint and the blurring between the natural and the built environments. Increasingly, humans, livestock and wildlife are interacting in new and unexpected ways, bringing new species – and their resident infections – together with unpredictable results.

Climate change is accelerating the loss of animal habitats and the ways humans change the land. Cutting down old-growth and rain forests, which harbour a rich biodiversity of life, to create agricultural or pastoral land potentially brings people and livestock in closer contact with previously isolated populations of bats, and other animals harbouring previously unencountered disease. In turn, biodiversity loss threatens natural food sources which means animals seek other sources of food found where people live. As climate change causes large disasters like floods and drought, human food sources are also lost, and growing food insecurity pushes people to further encroach on animal habitats, increasing animal contact and contributing to the trade in wildlife.

The speed and magnitude of environmental change has implications for future epidemics and pandemics. The first few cases of COVID-19 have been traced back to a ‘wet market’ that contained wild animals sold for food or medicines. Such markets can be ideal environments for zoonotic spread as the unusual mixing of animals (which is not common in the wild) can provide opportunities for viruses to jump between species, and potentially then to people.

Development isn't just loosing coronavirus — there are other pathogens that have been loosed by encroaching on their natural reservoirs:

We invade tropical forests and other wild landscapes, which harbor so many species of animals and plants — and within those creatures, so many unknown viruses. We cut the trees; we kill the animals or cage them and send them to markets. We disrupt ecosystems, and we shake viruses loose from their natural hosts. When that happens, they need a new host. Often, we are it.

The list of such viruses emerging into humans sounds like a grim drumbeat: Machupo, Bolivia, 1961; Marburg, Germany, 1967; Ebola, Zaire and Sudan, 1976; H.I.V., recognized in New York and California, 1981; a form of Hanta (now known as Sin Nombre), southwestern United States, 1993; Hendra, Australia, 1994; bird flu, Hong Kong, 1997; Nipah, Malaysia, 1998; West Nile, New York, 1999; SARS, China, 2002-3; MERS, Saudi Arabia, 2012; Ebola again, West Africa, 2014. And that’s just a selection. Now we have nCoV-2019, the latest thump on the drum.

The three viruses you mention are serious. MERS and SARS have high fatality rates. The third (SARS-CoV-2) is highly contagious. These attributes disrupt everyday life.

But the aforementioned and other viruses are also serious for similar reasons. Zika, for instance, can cause life-altering birth defects, has been known about for decades, and human-caused climate change has been enabling it to spread to more densely-populated areas.

Evolution — natural selection — takes place over thousands to millions of years. Human behavior has changed the earth only within a few hundred years, much of it in the last century or so.

  • $\begingroup$ Thanks for your response. I was definitely thinking that disruptions in the ecosystem such as climate change, deforestation and increased interaction with animals played a role like you said. Maybe my question wasn't clear enough, but I was focused specifically on if there was a reason why outbreaks caused specifically by coronaviruses have been happening in recent history. I appreciate your detailed response. $\endgroup$
    – Andrew
    Sep 4, 2020 at 0:51
  • $\begingroup$ There are a number of recent outbreaks caused specifically by other types of viruses, as well. But the answer to your question is no, zoonotic viruses are not becoming more prevalent due to evolution. $\endgroup$ Sep 4, 2020 at 4:28

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