How Viruses Evolve

By Bob Holmes

Knowable Magazine

The unusual cases of pneumonia began to appear in midwinter, in China. The cause, researchers would later learn, was a coronavirus new to science. By March, the infection began to spread to other Asian countries and overseas. People were dying, and the World Health Organization issued a global health alert.

But this was 2003, not 2020, and the disease was SARS, not Covid-19. By June, the outbreak was almost gone, with just 8,098 confirmed infections and 774 deaths worldwide. No cases of SARS have been reported since 2004.

Contrast that with the closely related coronavirus that causes Covid-19 today: more than 13,600,000 confirmed cases as of July 16, and more than 585,000 deaths.

Why did SARS go away while today’s coronavirus just keeps on spreading? Why, for that matter, did both these coronaviruses spill over into people at all, from their original bat hosts?

And just as vital as those questions is another: What happens next?

As we face the current pandemic, it will be important to understand how SARS-CoV-2, the virus that causes Covid-19, is likely to evolve in the months and years ahead. It’s possible the virus could lose its lethal character and settle into an evolutionary détente with humanity. It might end up as just another cold virus, as may have happened to another coronavirus in the past. But it could also remain a serious threat or perhaps even evolve to become more lethal. The outcome depends on the complex and sometimes subtle interplay of ecological and evolutionary forces that shape how viruses and their hosts respond to one another.

Continue to full article . . .

Picture: David Gregory & Debbie Marshall / CC BY (https://creativecommons.org/licenses/by/4.0)

Leave a Comment

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.