Strains of Coronavirus

How Many Coronaviruses Are There?

Coronaviruses didn’t just pop up recently. They’re a large family of viruses that have been around for a long time. Many of them can make people ill with sniffles or coughing. Before the SARS-CoV-2 outbreak, coronaviruses were thought to cause only mild respiratory infections in people.

The new (or “novel”) coronavirus is one of several known to infect humans. It’s probably been around for some time in animals. Sometimes, a virus in animals crosses over into people. That’s what scientists think happened here. So this virus isn’t new to the world, but it is new to humans. When scientists found out that it was making people sick in 2019, they named it as a novel coronavirus.

Human Coronavirus Types

Scientists have divided coronaviruses into four sub-groupings, called alpha, beta, gamma, and delta. Seven of these viruses can infect people:

  • 229E (alpha)
  • NL63 (alpha)
  • OC43 (beta)
  • HKU1 (beta
  • MERS-CoV, a beta virus that causes Middle East respiratory syndrome (MERS)
  • SARS-CoV, a beta virus that causes severe acute respiratory syndrome (SARS)
  • SARS-CoV-2, which causes COVID-19

Why Viruses Change

Coronaviruses have all their genetic material in something called RNA (ribonucleic acid). RNA has some similarities to DNA, but they aren’t the same.

When viruses infect you, they attach to your cells, get inside them, and make copies of their RNA, which helps them spread. If there’s a copying mistake, the RNA gets changed. Scientists call those changes mutations.

These changes happen randomly and by accident. It’s a normal part of what happens to viruses as they multiply and spread.

Because the changes are random, they may make little to no difference in a person’s health. Other times, they may cause disease. For example, one reason you need a flu shot every year is because influenza viruses change from year to year. This year’s flu virus probably isn’t exactly the same one that circulated last year.

If a virus has a random change that makes it easier to infect people and it spreads, that strain will become more common.

The bottom line is that all viruses, including coronaviruses, can change over time. Scientists and doctors call slightly different versions of a virus new strains.

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Second Coronavirus Strain

You might have heard that there’s more than one strain of the new coronavirus. Is it true? The answer appears to be yes.

The theory about different strains of the new coronavirus comes from a study in China. Researchers were studying changes in coronavirus RNA over time to figure out how various coronaviruses are related to each other. They looked at 103 samples of the new coronavirus collected from people, and they looked at coronaviruses from animals. It turned out that the coronaviruses found in humans weren’t all the same.

There were two types, which the researchers called “L” and “S.” They’re very similar, with slight differences in two places. It looks like the S type came first. But the scientists say the L type was more common early in the outbreak. One may cause more disease than the other. Scientists need more data to really know what these strains mean to human health and COVID-19.

What to Expect

As the coronavirus keeps spreading around the world, it will probably keep changing. Experts may find new strains. It’s impossible to predict how those virus changes might affect what happens. But change is just what viruses do.

WebMD Medical Reference Reviewed by Brunilda Nazario, MD on May 05, 2020

Sources

SOURCES:

National Institutes of Allergy and Infectious Diseases: “Coronaviruses.”

Nature Medicine: “The proximal origin of SARS-CoV-2.”

World Health Organization: “Coronavirus.”

CDC: “Coronavirus disease 2019 basics,” “Key facts about seasonal flu vaccine.”

Methods in Molecular Biology: “Coronaviruses: An Overview of Their Replication and Pathogenesis.”

Historyofvaccines.org: “Viruses and evolution.”

Nature: “A new coronavirus associated with human respiratory disease in China,” “We shouldn’t worry when a virus mutates during disease outbreaks.”

National Science Review: “On the origin and continuing evolution of SARS-CoV-2.”

CDC: “Human Coronavirus Types.”

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