Don’t shrug off your risk of COVID-19, especially if you’ve been in large crowds or other high-risk settings recently, simply because no symptoms were apparent in those nearby. This is an important public health message, one that needs amplifying after a World Health Organization communications fumble earlier this week.
On Monday, WHO epidemiologist Dr. Maria Van Kerkhove generated controversy when she responded to a question at one of WHO’s routine news conferences. Her answer lacked clarity and context. Reports afterward misleadingly summarized that transmission by asymptomatic people is “very rare.” Coverage also wrongly suggested that this was a new WHO position.
Medical experts responded with alarm and disbelief because the agency appeared to ignore accumulating research about COVID-19’s transmission by people before they develop symptoms. The statement also seemed to blow up one of the key rationales for social distancing. Indeed, some social media users quickly jumped to this simplistic conclusion: Since only those with COVID-19 symptoms are contagious, sick people can just stay home and no one else needs to worry about contracting it.
If only it were that easy. “WHO says asymptomatic transmission of COVID is very rare. Just ignore this. It is not true,” Mayo Clinic Dr. Vincent Rajkumar posted on Twitter.
In an interview with an editorial writer, renowned infectious disease expert Michael Osterholm also expressed concerns about the WHO statement and underscored the continued importance of social distancing. In addition, he said that the WHO effectively “walked back” its statement Tuesday morning.
The organization livestreamed a follow-up question-and-answer session with Van Kerkhove and another scientist, Dr. Michael Ryan, an Irish surgeon who heads the WHO’s emergency programs. Van Kerkhove swiftly clarified that people without symptoms can transmit the virus and that models show it plays a significant role in fueling COVID-19 transmission, though further study is needed.
Ryan pointed out that the Monday “statement” by Van Kerkhove was only a response to a reporter’s question. It did not represent an institutional shift in policy on asymptomatic spread or reverse any WHO position on population-wide mitigation measures needed to control COVID-19.
Much of the confusion appears rooted in what Van Kerkhove originally meant by “asymptomatic.” Some people infected do not go on to develop any symptoms. It’s not clear how unusual this is. Others may be “presymptomatic,” meaning they’re infected and later go on to develop symptoms. Van Kerkhove did not adequately distinguish between those groups in her original remarks.
It’s difficult to track infections spread by those who are asymptomatic.
That may explain why these individuals rarely appear to be a source of infection (our guess is that Van Kerkhove may have been trying to say something like this initially).
An April 15 study in the prestigious journal Nature estimated that “44% … of secondary cases were infected during the index cases’ presymptomatic stage.” The researchers call for mitigation measures reflecting this.
Said Osterholm: “This is not a time to let down our guard.”
— Star Tribune (Minneapolis)
