Robert Redfield, director of the Centers for Disease Control and Prevention, 25% of people infected with the new coronavirus don’t present any symptoms or fall ill, but they can still transmit the illness to others.
“One of the [pieces of] information that we have pretty much confirmed now is that a significant number of individuals that are infected actually remain asymptomatic,” Redfield told NPR on Tuesday.
These asymptomatic carriers, Redfield added, are likely contributing to the rapid spread of the coronavirus worldwide and making it challenging for experts to assess the true extent of the pandemic.
“We don’t know all the unidentified cases out there. It’s mostly sicker people in hospitals who are being tabulated,” Morse said.
The new findings are leading the CDC to broaden the range of who needs to wear medical masks, as they previously stated that only people showing symptoms should wear a mask.
Experts are urging the public to continue with social distancing, and they believe that everyone should be wearing masks to protect themselves against asymptomatic carriers spreading the virus.
The prevalence of asymptomatic transmission doesn’t bode well for global containment efforts, as Bill Gates recently wrote in an article published in the New England Journal of Medicine .
“That means COVID-19 will be much harder to contain than the Middle East respiratory syndrome or severe acute respiratory syndrome (SARS), which were spread much less efficiently and only by symptomatic people,” Gates said.
A World Health Organization report about the coronavirus outbreak in China, published in February, found very few instances in which a person who tested positive never showed any symptoms. Instead, the majority of people who were asymptomatic on the date of their diagnosis (a relatively small group anyway) went on to develop symptoms later.
“The proportion of truly asymptomatic infections is unclear but appears to be relatively rare,” the report authors wrote.
“This helps explain how rapidly this virus continues to spread across the country, because we have asymptomatic transmitters and we have individuals who are transmitting 48 hours before they become symptomatic,” he added.