Good advice is like a potent virus: It spreads far and wide rapidly.

That's exactly how one short 18-second video about what people ought to do this Covid-19 outbreak season has been like, as it became very popular online because of how simple and sensible it is.

This 18 seconds is probably the best single piece of advice I’ve heard about the #coronavirus pic.twitter.com/buDs1fhdwL

— Nooruddean (@BeardedGenius) March 13, 2020

It involves simply changing one's perspective of oneself to know how to act in the face of a contagious disease.

The advice was courtesy of Graham Medley, Professor of Infectious Disease Modelling at the London School of Hygiene and Tropical Medicine.

How to act in the face of Covid-19

In the clip, he told BBC Newsnight that people shouldn't act like they are avoiding contracting the virus.

Instead, they should act as someone who already has the virus and is trying not to pass it onto others.

"Most people have a fear of acquiring the virus. I think a good way of doing it is to imagine that you do have the virus, and change your behaviour so that you're not transmitting it," Medley said.

"Don't think about changing your behaviour so you won't get it. Think about changing your behaviour so you don't give it to somebody else."

Responses to best advice about Covid-19

This changing of stance was apparently enlightening to millions of people, who are in panic mode now because of the virus, and confused about the extent they should go to stay safe.

A version of the clip uploaded to Twitter on March 13 has been watched 2.6 million times and retweeted more than 38,000 times.

This advice has been hailed as "probably the best single piece of advice I've heard about the #coronavirus" by a Twitter user.

Source of good advice

But it turns out, the good advice also has a twist.

As the clip of Medley was shared widely, he admitted the suggestion had come from a BBC producer, Stuart Denman, just after he had filmed a Newsnight interview.

“It was so good I decided that I would say it instead, so they reset,” he tweeted.

“Think about your contacts – do you want to infect them? Our fight, our responsibility.”

Act like your infected, not avoiding infection. Wash your hands like you don’t want to transmit it. Think about your contacts - do you want to infect them? Our fight, our responsibility #Covid_19

— Graham Medley (@GrahamMedley) March 12, 2020

We had just finished filming an interview for @BBCNewsnight with @katierazz and the producer @StuartDenman said this. It was so good I decided that I would say it instead, so they reset

— Graham Medley (@GrahamMedley) March 12, 2020

Like a virulent strain of virus, the advice caught on.