EDIT: On Tuesday, the World Health Organization (WHO) walked back on comments that stated that asymptomatic and presymptomatic spread was "very rare."
Dr. Maria Van Kerkhove, head of the WHO’s emerging diseases and zoonosis unit, revealed that when it comes to COVID-19's spread much is still unknown. “We don’t actually have that answer yet,” she said.
“I was responding to a question at the press conference. I wasn’t stating a policy of WHO or anything like that. I was just trying to articulate what we know,” she said on a live Q&A. “And in that, I used the phrase ‘very rare,’ and I think that that’s misunderstanding to state that asymptomatic transmission globally is very rare. I was referring to a small subset of studies.”
Asymptomatic spread refers to when people contract the virus but never develop any symptoms, develop only mild symptoms, or only develop symptoms days after the infection. WHO officials now reveal that while this kind of spread does exist, it is not the dominant way the virus is transmitted.
Asymptomatic person transmitting to a secondary individual is 'very rare'
"From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual," Dr. Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit, said at a news briefing. "It’s very rare."
Van Kerkhove added that government responses should rely on isolating those with visible symptoms and tracking those who might have come into contact with them. When it comes to asymptomatic or presymptomatic spread, she explained that there was simply not enough research and data to “truly answer” the question of whether it occurs.
Contact tracing in countries
"We have a number of reports from countries who are doing very detailed contact tracing," she said. "They’re following asymptomatic cases. They’re following contacts. And they’re not finding secondary transmission onward. It’s very rare."
Still, Van Kerkhove did not dismiss asymptomatic and presymptomatic spread entirely, stating that it appears to still occur although rarely. These new findings will now influence how to screen for the virus and how to attempt to limit its spread.
Focusing on following the symptomatic cases
“What we really want to be focused on is following the symptomatic cases," Van Kerkhove said. "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."
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