Today's curveball comes from the World Health Organization, which said it's "very rare" for the coronavirus to spread through asymptomatic carriers.
Why it matters: Earlier evidence suggested person-to-person transmission among asymptomatics could spark runaway outbreaks, reports Axios' Marisa Fernandez.
- Young people and healthy people who did not experience symptoms were also suspected to be potential carriers to more vulnerable populations.
The big picture: The WHO is now relying on data obtained through contact tracing, said Maria Van Kerkhove, head of the emerging diseases and zoonosis unit.
- “We have a number of reports from countries who are doing very detailed contact tracing. They’re following asymptomatic cases. They’re following contacts. And they’re not finding secondary transmission onward. It’s very rare."
- In the press conference today, Van Kerkhove said there are fewer asymptomatic patients than previously thought.
- "[I]f you actually go back and say how many of them are truly asymptomatic, we find out that many have really mild disease, very mild disease, they’re not quote unquote COVID symptoms, meaning they may not have developed fever yet."
- She later called attention to WHO guidance on face masks released Friday, which included a section on asymptomatic spread. (Page 2 of the download).
Between the lines: Don't treat these statements as a "get out of social distancing" free card.
- Infected people can be contagious well before experiencing symptoms.
- "Some modeling studies suggest 40–60% of spread is from people when they didn’t have symptoms," tweeted Ashish Jha, incoming dean at the Brown School of Public Health.
- Singapore's coronavirus task force also said today that it believes half of the country's new COVID-19 cases are asymptomatic based on testing data, Reuters reports.
The bottom line: These statements are a reminder of just how little we understand about this virus.