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 W.H.O. 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 W.H.O.’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 W.H.O. 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 W.H.O. 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 United States, adopted lockdown strategies because they recognized that isolating only people who were sick might not be enough to contain the epidemic.
If the virus is transmitted by small airborne droplets, people will need to continue to avoid congregating in poorly ventilated spaces, even if they practice rigorous hand hygiene.
The W.H.O. 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 W.H.O. 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 W.H.O. to give us the best scientific data and evidence.”
The W.H.O.’s thinking on asymptomatic transmission does not appear to have changed much since February, when the W.H.O. 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 percent; the current best estimate from the Centers for Disease Control and Prevention is 35 percent. The research prompted many countries, including the United States, to endorse use of masks by everyone.
But on Monday, Dr. Maria Van Kerkhove, the W.H.O.’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 W.H.O. 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 W.H.O. 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 W.H.O.
But critics, including its own officials, said the organization should be transparent about its sources. “W.H.O.’s first and foremost responsibility is to be the science leader,” said Lawrence Gostin, director of the W.H.O. Collaborating Center on National and Global Health Law.
“And 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 percent of new infections were a result of transmission from people who were not yet showing symptoms.
W.H.O. 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, W.H.O. 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 W.H.O. 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 recognized is that activities like coughing and talking, even breathing in some cases, are also aerosol-producing procedures,” said Linsey Marr, who studies airborne transmission of viruses at Virginia Tech.
Frequently Asked Questions and Advice
Updated June 5, 2020
Does asymptomatic transmission of Covid-19 happen?
So far, the evidence seems to show it does. A widely cited paper published in April suggests that people are most infectious about two days before the onset of coronavirus symptoms and estimated that 44 percent of new infections were a result of transmission from people who were not yet showing symptoms. Recently, a top expert at the World Health Organization stated that transmission of the coronavirus by people who did not have symptoms was “very rare,” but she later walked back that statement.
How does blood type influence coronavirus?
A study by European scientists is the first to document a strong statistical link between genetic variations and Covid-19, the illness caused by the coronavirus. Having Type A blood was linked to a 50 percent increase in the likelihood that a patient would need to get oxygen or to go on a ventilator, according to the new study.
How many people have lost their jobs due to coronavirus in the U.S.?
The unemployment rate fell to 13.3 percent in May, the Labor Department said on June 5, an unexpected improvement in the nation’s job market as hiring rebounded faster than economists expected. Economists had forecast the unemployment rate to increase to as much as 20 percent, after it hit 14.7 percent in April, which was the highest since the government began keeping official statistics after World War II. But the unemployment rate dipped instead, with employers adding 2.5 million jobs, after more than 20 million jobs were lost in April.
Will protests set off a second viral wave of coronavirus?
Mass protests against police brutality that have brought thousands of people onto the streets in cities across America are raising the specter of new coronavirus outbreaks, prompting political leaders, physicians and public health experts to warn that the crowds could cause a surge in cases. While many political leaders affirmed the right of protesters to express themselves, they urged the demonstrators to wear face masks and maintain social distancing, both to protect themselves and to prevent further community spread of the virus. Some infectious disease experts were reassured by the fact that the protests were held outdoors, saying the open air settings could mitigate the risk of transmission.
How do we start exercising again without hurting ourselves after months of lockdown?
Exercise researchers and physicians have some blunt advice for those of us aiming to return to regular exercise now: Start slowly and then rev up your workouts, also slowly. American adults tended to be about 12 percent less active after the stay-at-home mandates began in March than they were in January. But there are steps you can take to ease your way back into regular exercise safely. First, “start at no more than 50 percent of the exercise you were doing before Covid,” says Dr. Monica Rho, the chief of musculoskeletal medicine at the Shirley Ryan AbilityLab in Chicago. Thread in some preparatory squats, too, she advises. “When you haven’t been exercising, you lose muscle mass.” Expect some muscle twinges after these preliminary, post-lockdown sessions, especially a day or two later. But sudden or increasing pain during exercise is a clarion call to stop and return home.
My state is reopening. Is it safe to go out?
States are reopening bit by bit. This means that more public spaces are available for use and more and more businesses are being allowed to open again. The federal government is largely leaving the decision up to states, and some state leaders are leaving the decision up to local authorities. Even if you aren’t being told to stay at home, it’s still a good idea to limit trips outside and your interaction with other people.
What’s the risk of catching coronavirus from a surface?
Touching contaminated objects and then infecting ourselves with the germs is not typically how the virus spreads. But it can happen. A number of studies of flu, rhinovirus, coronavirus and other microbes have shown that respiratory illnesses, including the new coronavirus, can spread by touching contaminated surfaces, particularly in places like day care centers, offices and hospitals. But a long chain of events has to happen for the disease to spread that way. The best way to protect yourself from coronavirus — whether it’s surface transmission or close human contact — is still social distancing, washing your hands, not touching your face and wearing masks.
What are the symptoms of coronavirus?
Common symptoms include fever, a dry cough, fatigue and difficulty breathing or shortness of breath. Some of these symptoms overlap with those of the flu, making detection difficult, but runny noses and stuffy sinuses are less common. The C.D.C. has also added chills, muscle pain, sore throat, headache and a new loss of the sense of taste or smell as symptoms to look out for. Most people fall ill five to seven days after exposure, but symptoms may appear in as few as two days or as many as 14 days.
How can I protect myself while flying?
If air travel is unavoidable, there are some steps you can take to protect yourself. Most important: Wash your hands often, and stop touching your face. If possible, choose a window seat. A study from Emory University found that during flu season, the safest place to sit on a plane is by a window, as people sitting in window seats had less contact with potentially sick people. Disinfect hard surfaces. When you get to your seat and your hands are clean, use disinfecting wipes to clean the hard surfaces at your seat like the head and arm rest, the seatbelt buckle, the remote, screen, seat back pocket and the tray table. If the seat is hard and nonporous or leather or pleather, you can wipe that down, too. (Using wipes on upholstered seats could lead to a wet seat and spreading of germs rather than killing them.)
How do I take my temperature?
Taking one’s temperature to look for signs of fever is not as easy as it sounds, as “normal” temperature numbers can vary, but generally, keep an eye out for a temperature of 100.5 degrees Fahrenheit or higher. If you don’t have a thermometer (they can be pricey these days), there are other ways to figure out if you have a fever, or are at risk of Covid-19 complications.
Should I wear a mask?
The C.D.C. has recommended that all Americans wear cloth masks if they go out in public. This is a shift in federal guidance reflecting new concerns that the coronavirus is being spread by infected people who have no symptoms. Until now, the C.D.C., like the W.H.O., has advised that ordinary people don’t need to wear masks unless they are sick and coughing. Part of the reason was to preserve medical-grade masks for health care workers who desperately need them at a time when they are in continuously short supply. Masks don’t replace hand washing and social distancing.
What should I do if I feel sick?
If you’ve been exposed to the coronavirus or think you have, and have a fever or symptoms like a cough or difficulty breathing, call a doctor. They should give you advice on whether you should be tested, how to get tested, and how to seek medical treatment without potentially infecting or exposing others.
How do I get tested?
If you’re sick and you think you’ve been exposed to the new coronavirus, the C.D.C. recommends that you call your healthcare provider and explain your symptoms and fears. They will decide if you need to be tested. Keep in mind that there’s a chance — because of a lack of testing kits or because you’re asymptomatic, for instance — you won’t be able to get tested.
W.H.O. 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 W.H.O.’s technical lead on the coronavirus.
But the W.H.O. defines airborne transmission too narrowly, some scientists said. Airborne transmission also includes the possibility that the virus is aloft for shorter distances, then inhaled.
“They have a very early 20th century, very unsophisticated view of what aerosols and airborne transmission are,” said Dr. Don Milton, an expert on public health aerobiology at the University of Maryland.
Up until the 1950s, Dr. Milton said, tuberculosis was thought to be spread by prolonged close contact. “We now know that it’s only transmitted by aerosols,” he said.
Some scientists are suspicious that W.H.O.’s stance on masks and aerosols may stem less from scientific research than from a concern over supplies of personal protective equipment for medical workers.
The organization currently recommends respirator masks that would block aerosols only for health care workers doing medical procedures that produce aerosols.
Dr. Van Kerkhove said that the W.H.O.’s guidance was based only on science and not on any considerations of supply. While a shortage of P.P.E. is a problem, she said, “it doesn’t change what we recommend.”
All of the experts said it was not that the W.H.O. 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.
“We don’t know,” Dr. Milton said. “But they also don’t know.”
Some experts said that when the W.H.O. uses the phrase “there is no evidence” to indicate uncertainty, it is in fact conveying certainty about the absence of a phenomenon.
Dr. Van Kerkhove conceded that point.
“That’s a fair statement,” she said. “There’s a lot of research that needs to be done to really understand this, and we are open to the fact that there is new research every day.”