A World Health Organization leader said on Monday that it has found data that suggests that asymptomatic spread of the coronavirus is “very rare,” while another expert cautioned the findings.
Dr. Maria Van Kerkhove, who is a WHO expert on infectious diseases, said that while those who don’t display coronavirus symptoms are capable of spreading the virus, those with symptoms are much more likely of spreading the virus.
“We have a number of reports from countries who are doing very detailed contact tracing,” Dr. Van Kerkhove said. “They’re following asymptomatic cases. They’re following contacts. And they’re not finding secondary transmission onward. It’s very rare.”
But another prominent infectious disease expert rebutted Dr. Van Kerkhove’s interpretation of the data. Dr. Ashish Jha, the director of Harvard’s Global Health Institute, said in response to Dr. Van Kerkhove’s anaylsis, “Asymptomatic spread is Achille’s heal of this outbreak.”
“Both asymptomatic and pre-symptomatic spread huge problem for controlling disease because folks shedding virus while asymptomatic pre-symptomatic has one advantage: You can use contact tracing to find folks they infected,” he said. “But that doesn’t help prevent pre-symptomatic spread”
Dr. Jha cited a May Swiss study that indicated that between 40 and 60% of all coronavirus cases originated from people when they didn’t have symptoms at the time of the spread.
Dr. Van Kerkhove said that based on the data she has seen, in many cases, when they go back and find coronavirus cases through contact tracing, many infected with the virus have “really mild disease.”
“They are not ‘COVID’ symptoms,” Dr. Van Kerkhove said. “They may not have developed a fever yet, they may not have had a significant cough or they may not have shortness of breath. But some may have mild disease.”
Dr. Van Kerkhove said that the WHO is still requesting countries to contribute data to allow the organization to better understand the spread of the virus.
“What we really want to be focused on is following the symptomatic cases,” she said. “If we followed all the symptomatic cases, because we know it is a respiratory pathogen, it passes to a person from infectious droplets. If we actually followed all of the symptomatic cases, isolated those cases, followed the contacts and quarantined those contacts, we would drastically reduce” the outbreak.
Last month, the CDC released data that indicated that 35% of those infected with the virus are asymptomatic.