A South Korean study suggested that people without symptoms may carry an amount of the virus equivalent to that in the body of those with symptoms.
South Korea was able to identify and isolate asymptomatic cases through mass testing as early as early March.
It is increasingly clear that these cases represent a considerable proportion of coronavirus infections.
But the researchers were unable to say to what extent these people actually transmitted the virus.
People who tested positive for the coronavirus were followed up at a community treatment center, allowing scientists to examine the amount of virus detectable in their nasal and pharyngeal swabs.
They underwent regular testing, and were only released when they tested negative.
Results from 1,886 tests suggest that people without symptoms at the time of the test, including those who never develop symptoms, have the same amount of virus in their nose and throat as people with symptoms.
The study also showed that the virus can be detected in asymptomatic people for a significant period of time – although they seem to clear it from their system a bit faster than people with symptoms.
The median time (the number of cases where half of the cases were higher and the other half lower) from diagnosis to test negative was 17 days in asymptomatic patients and 19.5 days in symptomatic patients.
Due to the nature of the isolation center, the study did not include people with severe cases of the disease. These people were also younger and healthier than average.
Most coronavirus tests, including in the UK, focus on people with symptoms, so there is little data on asymptomatic cases.
This study gives us some additional information about their appearance in the body.
The researchers admit, however, that their study could not “determine the role” that the presence of the virus in asymptomatic patients played in transmission.
In theory, having the same amount of virus in your nose and throat means you have just as much to transmit.
But people who don’t have symptoms are less likely to have a pungent cough that will send the infected droplets further into the air.
There is “as much virus in their respiratory mucus as a person with the disease,” says Dr Simon Clarke, a cell microbiologist at the University of Reading.
But, he adds, “that doesn’t mean they spray so much in the environment.”
While there is always a risk for people without symptoms, a person with symptoms who “coughs and sprays the virus” is likely to be at higher risk, he says.
The risks of contracting coronavirus depend on several factors, said Dr Andrew Preston, infection biologist at the University of Bath.
This includes how deep and quickly the infected person breathes, how long they are close to them, and whether or not they are in a closed environment, he added.
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Author: BBC-Africa – BBC-Africa
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