Trending Clinical Topic: Asymptomatic COVID-19

Ryan Syrek


June 12, 2020

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Around the world, as restrictions originally put in place to slow the spread of coronavirus are being eased, concerns about individuals who are asymptomatically infected resulted in this week's top trending clinical topic. Many are concerned about the easing of lockdown and distancing measures, while others argue that some policies are too restrictive. The role that asymptomatic infections play in the spread of COVID-19 is a subject of increasing scrutiny.

The World Health Organization (WHO) came under fire earlier this week when one of its experts suggested that asymptomatic coronavirus could not transmit easily from person to person. Anthony Fauci, MD, of the White House Coronavirus Task Force, criticized the remarks, and the organization quickly walked the comments back.

Although the WHO notes that few reports have described truly asymptomatic cases, some studies are emerging that potentially quantify the issue. Findings published in the journal Thorax describe testing performed on all passengers and crew of an isolated cruise ship. A sizeable majority of those who tested positive for COVID-19 were asymptomatic (see Infographic below).

A study of pregnant women with a planned delivery during the first half of April, published in Obstetrics & Gynecology, found that the rate of asymptomatic SARS-CoV-2 infection was 16%. Among those individuals designated as support persons for the pregnant women, the asymptomatic carrier rate was 10%. Meanwhile, a report out of China details 300 asymptomatic carriers of the novel coronavirus who were found not to be infectious.

The term "asymptomatic" may be something of a misnomer. As Ian Mackay, a virologist at the University of Queensland, told Reuters, close inspection of allegedly asymptomatic cases is likely to reveal something that "probably fits with a more realistic mild disease" than explicitly asymptomatic. Whether or not such individuals have absolutely no symptoms, the concern is that such infections are hard to identify and isolate.

Among the more innovative methods of identifying the presence of asymptomatic or presymptomatic COVID-19 is the possible use of bio-detection dogs. The United Kingdom is investigating whether specialist medical sniffer dogs are able to detect the presence of SARS-CoV-2 in humans who are not displaying symptoms. As farfetched as it may sound, such dogs have already been used to identify distinctive odors associated with some cancers, malaria, and Parkinson disease.

Because many of the prevention strategies that will soon be in place hinge on recognizing and separating infected individuals, asymptomatic COVID-19 is likely to continue as a top trending clinical topic.

Read more clinical information about COVID-19.


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