The World Health Organization made noise Monday when the head of its emerging diseases and zoonosis unit, Dr. Maria Van Kerkhove, said during a briefing that transmission of the novel coronavirus by asymptomatic carriers is “very rare.”
Citing data WHO has collected, Van Kerkhove said spread from asymptomatic and presymptomatic people does occur, but recommended focusing on tracing and isolating symptomatic people to better attack the outbreak.
While the comments drew questions from experts on Twitter, it may simply be an issue of semantics, with Dr. Isaac Bogoch and Dr. Allan Detsky of the University of Toronto previously pointing out the misuse of the term “asymptomatic” when referring to “presymptomatic” patients.
While asymptomatic people never show signs of the coronavirus, presymptomatic people exhibit no signs of contracting the disease for the first few days before experiencing the classic symptoms.
Dr. Ashish K. Jha, director at the Harvard Global Health Institute, tweeted out the distinction and noted that the agency “should be clearer in communication, also noting that some models “suggest 40-60% of spread is from people when they didn’t have symptoms.”
The fact that symptoms aren’t immediately present in people that have contracted the virus is a key reason for containment measures and safety protocols like masks, with the U.S. Centers of Disease Control and Prevention writing in April, “The potential for presymptomatic transmission underscores the importance of social distancing, including the avoidance of congregate settings, to reduce Covid-19 spread.”
Van Kerkhove also stated that seemingly asymptomatic carriers just didn’t recognize the signs of the virus: “When we actually go back and say, ‘How many of them were truly asymptomatic?’ we find out that many have really mild disease, very mild disease.”
“Comprehensive studies on transmission from asymptomatic individuals are difficult to conduct, but the available evidence from contact tracing reported by Member States suggests that asymptomatically-infected individuals are much less likely to transmit the virus than those who develop symptoms,” Van Kerkhove later tweeted.
The CDC in early April began recommending people wear cloth face coverings when out in public due to studies that show asymptomatic or presymptomatic people are able to spread the disease as well. Understanding the characteristics and spread of Covid-19 has been an ongoing challenge throughout the pandemic, as characterized by the continuing questions surrounding the spread of the disease before symptoms set in. There are 7,085,894 confirmed cases globally, with the U.S. leading with 1,956,499. The U.S. also leads with reported deaths with 110,932 out of the globe’s total 405,168.
50%. That’s the portion of new cases Singapore confirmed on Monday that were symptomless, according to Reuters.