A deeply entrenched idea, that newly emerged agents of disease inevitably evolve to become more benign over time, is scientifically unfounded, according to new research.
They can, in fact, become more virulent depending on the conditions, and the easier it is for a virus to spread, the more likely it is to do so.
The findings suggest that failing to control outbreaks of Covid-19 – or even deliberately encouraging the circulation of the Sars-CoV-2 virus that causes it, as some lockdown sceptics have proposed – could increase the the chance of more harmful forms of the virus emerging in the short term.
Public health experts have been warning for months that trying to achieve herd immunity by letting the virus circulate more-or-less freely is dangerous because it could lead to unnecessary deaths and health services being overwhelmed.