Shifting goalposts: When WHO stumbles, a pattern emerges
Experts contend that the agency’s advice sometimes lags behind rapidly evolving research into the coronavirus
Even as the World Health Organization leads the worldwide response to the coronavirus pandemic, the agency is failing to take stock of rapidly evolving research findings and to communicate clearly about them, several scientists warned on Tuesday. In a news briefing on Monday, a WHO official asserted that transmission of the coronavirus by people without symptoms is “very rare.” Following concerted pushback from researchers, officials on Tuesday walked back the claim, saying it was a “misunderstanding.”
But it is not the first time the WHO’s assessment has seemed to lag behind scientific opinion. The agency delayed endorsing masks for the general public until Friday, claiming there was too little evidence that they prevented transmission of the virus. Virtually all scientists and governments have been recommending masks for months. The WHO has said repeatedly that small airborne droplets, or aerosols, are not a significant factor in the pandemic’s spread, although a growing body of evidence suggests that they may be.
“The WHO has been out of step with most of the world on the issue of droplets and aerosols,” said Michael Osterholm, an infectious disease expert at the University of Minnesota. These scientific disagreements have wide policy implications. Many countries, including the US, adopted lockdown strategies because they recognised that isolating only people who were sick might not be enough to contain the epidemic. If the virus is transmitted by airborne droplets, people will need to continue to avoid congregating in poorly ventilated spaces, even if they practice hand hygiene.
The WHO traditionally has taken a cautious approach to evaluating scientific evidence. But the pace of research has changed: Now scientists are rushing to publish preliminary research, even before their results can be thoroughly vetted by other experts. The avalanche of findings may bring advances — like a vaccine — in record time. But the onslaught also has led to confusion, even retractions of high-profile results. “On the one hand, I do want to cut the WHO some slack, because it is hard to do this in an evolving pandemic,” said Dr Ashish Jha, director of the Harvard Global Health Institute. “At the same time, we do rely on the WHO to give us the best scientific data and evidence.”
The WHO’s thinking on asymptomatic transmission does not appear to have changed much since February, when the WHO China Joint Mission reported that “the proportion of truly asymptomatic infections is unclear, but appears to be relatively rare and does not appear to be a major driver of transmission.”
Studies later estimated this number could be as high as 40%; the current best estimate from the Centers for Disease Control and Prevention is 35%. The research prompted many countries, including the US, to endorse use of masks by everyone.
But on Monday, Dr Maria Van Kerkhove, the WHO’s technical lead for coronavirus response, said that “it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual.” Her statement provoked an immediate backlash from scientists, who noted that study after study had shown transmission of the virus from people before they ever felt symptoms. The reaction prompted the WHO to clarify its position in a live session hosted on Facebook and Twitter. Dr Van Kerkhove said her comment had been based on only two or three studies. “I was just responding to a question, I wasn’t stating a policy of WHO or anything like that,” she said. Dr Van Kerkhove said her statement was also based on unpublished evidence that some countries have shared with the WHO.
But critics, including its own officials, said the organization should be transparent about its sources. “WHO’s foremost responsibility is to be the science leader,” said Lawrence Gostin, director, WHO Collaborating Center on National and Global Health Law. “When they come out with things that are clearly contradicted by the scientific establishment without any justification or citing studies, it significantly reduces their credibility.”
A key point of confusion is the difference between people who are “pre-symptomatic” and will go on to develop symptoms, and those who are “asymptomatic” and never feel sick. Dr Van Kerkhove suggested that her comments were about people who are truly asymptomatic. A widely cited paper published in April suggested that people are most infectious up to two days before the onset of symptoms, and estimated that 44% of new infections were a result of transmission from people who were not yet showing symptoms. WHO refers to such people as pre-symptomatic. “OK, technically fine,” Dr Jha said. “But for all intents and purposes, they are asymptomatic — they are without symptoms.” Dr Van Kerkhove said that by using the two terms, WHO officials are in fact trying to be very clear about the group of people they are referring to.
“Unfortunately, that’s not how everybody uses it,” she said. “I didn’t intend that to make things more complicated.” The WHO continues to maintain that large respiratory droplets expelled by sneezing or coughing are the main route of transmission and to downplay a possible role for aerosols, smaller particles that may linger in the air. But evidence is piling up that aerosols may be an important route. “What they haven’t recognised is that coughing and talking, even breathing in some cases, are aerosol-producing procedures,” said Linsey Marr, who studies airborne transmission of viruses at Virginia Tech.
WHO officials said they were aware that breathing and talking might result in aerosols, but questioned their importance in spreading the virus. “To date, there has been no demonstration of transmission by this type of aerosol route,” said Dr Benedetta Allegranzi, the WHO’s technical lead on the coronavirus. But the WHO defines airborne transmission too narrowly, some scientists said. Airborne transmission also includes the possibility that the virus is aloft for shorter distances, then inhaled. All of the experts said it was not that the WHO is wrong on all counts, but that given the implications of its statements, it should be more cautious in concluding that transmission by air or by people without symptoms is not significant.
— Apoorva Mandavilli is science and global health reporter for NYT© 2020
The New York Times