A recent study in the scientific publication Morbidity and Mortality Weekly Report (MMWR), which is prepared by the Centers for Disease Control and Prevention (CDC), shows just how quickly SARS-CoV-2, which is the virus that causes COVID-19, can spread.

The study, which focused on a long-term care skilled nursing facility in King County, Washington, looked at what happened after it was discovered that a health care worker there had COVID-19. Of the 82 people who lived at the facility, 76 were tested for SARS-CoV-2. Of those, 23 (or 30.3% of the residents) tested positive for SARS-CoV-2.

In addition, about half of those who tested positive didn't have any symptoms (they were asymptomatic) when they were tested or they developed symptoms later on after they were tested (they were presymptomatic).

While the study's findings are new, the case data dates back to when the coronavirus crisis struck Washington state in late February and early March. The report highlights just how infectious the virus is, especially when it's spread by people who don't realize they're even sick.

Read the full study here on the CDC site.