In fact, in many cases, it seemed that the one to two days before a person manifested symptoms was when COVID-19 was possibly most contagious.

The latent period is often shorter than the incubation period in SARS-2, but that was generally not the case in SARS-1. The difference between the latent period and the incubation period is sometimes known as the mismatch period; it’s calculated by measuring the incubation period and subtracting the latent period. The difference between these two p

One of these features, paradoxically, was that SARS-1 was actually too deadly. Epidemiologists quantify the lethality of pathogens in two primary ways. The infection fatality rate (IFR) is the probability a person will die if he or she gets infected. The case fatality rate (CFR) is the probability a person will die after being diagnosed with the co

A new pathogen has been introduced into our species, and in some form, it will now circulate among us forever.

Scientists later came to suspect that this initial move by the virus might have happened at the Huanan Seafood Wholesale Market in Wuhan, because many of the first recorded patients were vendors or visitors there. But the picture was confusing. Huanan is known as a wet market because, as at many other markets throughout the world, one can buy fresh

This variation in R0 across individuals in a population can be quantified, and this quantity can have subtle but important effects on the course of an epidemic. The higher this variation (or dispersion), the more likely an epidemic will feature both super-spreading events and dead-end transmission chains. That is, an epidemic involving a population

In terms of evolutionary biology, the virus has had what is known as an “ecological release.” This refers to the expansion of range and the population explosion that occurs when a species is freed from constraints it previously faced. The typical example of this is invasive species introduced by humans such as the cane toads that overwhelmed Austra

While the coronavirus causing the 2020 pandemic is new, we have lived with other coronaviruses for a long time. In our species, four types of coronavirus are endemic, meaning we have reached a détente with these pathogens.

For SARS-1, the R0 was computed to be in the range of 2.2 to 3.6, and it’s probably between 2.6 and 3.0.