The word “asymptomatic” is causing quite a stir and confusion among Covid-19 experts and the public, after Maria Van Kerkhove, MD, the WHO’s technical lead on Covid-19, stated during a press conference that asymptomatic transmission is “very rare.”
However, she has since walked back and clarified her statement, noting that the true number of asymptomatic cases is not yet known.
This was not a good enough explanation for Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases.
He noted during an interview that there is evidence that some 25%-45% of people infected with Covid-19 do not exhibit symptoms, CNN Health reported.
“And we know from epidemiological studies they can transmit to someone who is uninfected even when they’re without symptoms. So, to make a statement to say that’s a rare event was not correct,” he stated.
As the pandemic continues to evolve, so do the words used to describe it. For example, asymptomatic — someone without Covid-19 symptoms and who never develops symptoms but may have mild disease; and pre-symptomatic — someone who does not yet have symptoms but goes on to develop full-fledged overt symptoms of the disease.
And there’s the rub, as what has been dubbed asymptomatic may actually be pre-symptomatic spread, or both.
“The WHO created confusion yesterday when it reported that asymptomatic patients rarely spread the disease,” an email from the Harvard Global Health Institute said Tuesday, according to Stat News. “All of the best evidence suggests that people without symptoms can and do readily spread SARS-CoV-2, the virus that causes Covid-19. In fact, some evidence suggests that people may be most infectious in the days before they become symptomatic — that is, in the presymptomatic phase when they feel well, have no symptoms, but may be shedding substantial amounts of virus.”
And CNN Health noted in its report that “Detailed contact tracing from Taiwan as well as the first European transmission chain in Germany suggested that true asymptomatics rarely transmit,” said Babak Javid, a principal investigator at Tsinghua University School of Medicine in Beijing and an infectious disease consultant at Cambridge University Hospitals.
“However, those (and many other) studies have found that paucisymptomatic transmission (meaning they have extremely mild symptoms) can occur, and in particular, in the German study, they found that transmission often appeared to occur before or on the day symptoms first appeared.”
Van Kerkhove set off the war of words and their meaning when on Monday, June 8, she answered a reporter’s question about a report from Singapore that showed about half of its cases were asymptomatic, and Van Kerkhove noted that such cases have been identified by contact tracing.
“We have a number of reports from countries who are doing very detailed contact tracing. They’re following asymptomatic cases, they’re following contacts and they’re not finding secondary transmission onward. It’s very rare, and much of that is not published in the literature,” she noted.
In her lengthy response, Van Kerkhove noted that the focus needs to be on following symptomatic cases. “If we followed all of the symptomatic cases — because we know that this is a respiratory pathogen, it passes from an individual through infectious droplets — if we followed all of the symptomatic cases, isolated those cases, followed and quarantined those contacts, we would drastically reduce [transmission]… If we could focus on that, I think we would do very, very well in terms of suppressing transmission.”
She reiterated her perception that asymptomatic transmission is rare:
“But from the data we have, it still seems to be rare that an asymptomatic actually transmits onward to a secondary individual.”
Candace Hoffmann, Managing Editor, BreakingMED™
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