Suspicion about the possibility of “stealth transmission” has been growing since mid-February, when Dr. Sandra Ciesek, director of the University of Frankfurt’s Institute for Medical Virology, reported in the New England Journal of Medicine that, in a lab, she had been able to infect human cells with coronavirus samples taken from two airline passengers returning to Germany from Wuhan, China. While both tested positive for the virus, one of the travelers had no symptoms and the other reported a mild sore throat and rash. (LA Times)

“Undetected cases can expose a far greater portion of the population to [the] virus than would otherwise occur. … These “stealth transmissions” will continue to present a major challenge to the containment of this outbreak going forward,” Shaman said. (Live Science)

The researchers said while these findings “indicate containment of this virus will be particularly challenging,” they did find that social distancing and quarantines slowed the spread of the virus. When they ran simulations occurring between Jan. 24 and Feb. 8, as diagnostic efforts increased, they found that stealth transmission dropped by a factor of five and transmission rates among documented patients dropped by at least 50%. (Advisory)