Indonesian photographer Joshua Irwandi captured one of the most chilling and poignant images of Covid-19's toll.

In a world where no one has immunity, infectious diseases spread exponentially. That’s what happened early in the Covid pandemic ... you’d need to prevent 17 of 18 infections, or over 94 ...

"Silent" COVID-19 infections—cases in which individuals carried the virus without symptoms and avoided testing or isolation—likely exacerbated the pandemic's early spread and distorted ...