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How the virus behind COVID-19 is evolving across the world

Newshub logoNewshub 30/03/2020 Dan Satherley
a close up of a glass: NZ's Monday update on the COVID-19 pandemic. © Video - Newshub; Images - Getty NZ's Monday update on the COVID-19 pandemic.

Scientists studying the evolution of the virus behind COVID-19 say there are at least eight distinct strains of the disease.

But it's evolving very slowly by viral standards, raising hopes it won't become a seasonal disease like influenza.

"The virus mutates so slowly that the virus strains are fundamentally very similar to each other," University of California infectious disease specialist Charles Chiu told USA Today. 

Influenza mutates eight to 10 times faster than SARS-CoV-2, according to Kristian Andersen of Scripps Research in California. It requires a new vaccine every year, and it's not even guaranteed to work - studies have found it's only 67 percent effective, the flu virus mutates so fast. 

Dr Andersen's team last week released evolutionary evidence they said proved COVID-19 isn't a bioweapon. 

The latest evidence, found on genetic tracking site nextstrain.org, shows the virus splitting into different types in different parts of the world. The strain present in New Zealand, according to a map released by nextstrain.org, shows it's the same one they currently have in Australia. It's also present in parts of southeast Asia.

"The outbreaks are trackable. We have the ability to do genomic sequencing almost in real-time to see what strains or lineages are circulating," said Dr Chiu.

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The virus' slow mutation is probably because it's highly infectious - it's not under any evolutionary pressure to evolve, said Dr Andersen. Though it's still early days for researchers, it appears the SARS-CoV-2 virus is twice as infectious as influenza. 

This is good news, as it means the virus is unlikely to spontaneously evolve into a more deadly variant.

The wide range in mortality rates recorded across the world are unlikely to be the result of the eight different strains detected so far, Dr Chiu said.

The virus' genome has about 30,000 base pairs - only about 11 of those have changed since a strain of the virus from its origin in China was first sequenced in early January.

"The current virus strains are still fundamentally very similar to each other," he told USA Today

Instead, it's likely mortality is about the same across the world - the differences down to different rates of testing, rather than the virus itself. 

Same goes for the severity of symptoms - some people have none, most have a mild illness, while others end up in hospital and some die.

New Zealand has had one death so far and nearly 600 confirmed infections.

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