WHO clarifies comments on asymptomatic spread of Covid-19
Andrew Joseph
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“The WHO created confusion yesterday when it reported that asymptomatic patients rarely spread the disease,” an email from the Harvard Global Health Institute said Tuesday. “All of the best evidence suggests that people without symptoms can and do readily spread SARS-CoV-2, the virus that causes Covid-19. In fact, some evidence suggests that people may be most infectious in the days before they become symptomatic — that is, in the presymptomatic phase when they feel well, have no symptoms, but may be shedding substantial amounts of virus.”
Their point: People not showing symptoms can spread the virus, whether they ultimately feel sick or not. That’s why wearing masks and keeping distance are so important to limiting transmission.
Van Kerkhove acknowledged Tuesday that her use of the phrase “very rare” had been a miscommunication. She said she had based that phrasing on findings from a small number of studies that followed asymptomatic cases and tracked how many of their contacts became infected. She said she did not mean to imply that “asymptomatic transmission globally” was happening rarely, because that has not been determined yet.
Determining which routes of transmission are driving most of the spread of the virus is crucial so health experts can develop the right strategies to combat the virus. At the WHO event Tuesday, officials stressed that even as scientists are still learning more about the virus and how it spreads, countries have demonstrated that the best tactics to address the pandemic include isolating cases, contact tracing, and quarantining contacts — as well as hand hygiene and respiratory etiquette.
With those measures, “We won’t stop all transmission, but what we do is, we suppress transmission,” Mike Ryan, the head of WHO’s emergencies program, said Tuesday.