A South Korean study has suggested that asymptomatic COVID-19 patients can carry the same amount of virus as those with symptoms. 

File photo: VCG

The study published in the JAMA Internal Medicine journal adopted a testing method called RT-PCR to identify SARS-CoV-2, the virus responsible for COVID-19. The findings were based on samples from 303 young and otherwise healthy patients isolated in a community treatment center in South Korea. 

Roughly a third of those sampled had no symptoms when they were diagnosed, and about 20 percent of this group developed symptoms while isolated. Multiple tests over the course of about a month showed similar viral loads in people with or without symptoms.

After 1,886 sample tests, the researchers found that asymptomatic patients carried high loads of SARS-CoV-2 in their nose, throat and lungs, and the loads tend to decrease more slowly than in patients who show symptoms.

The study also showed that the virus could still be detected in asymptomatic patients for a period of time, although these patients seem to clear the virus from their systems slightly faster than people with symptoms.  

The researchers said the findings could help people understand what portion of infected people is truly asymptomatic rather than merely "pre-symptomatic." However, the study did not determine how much role asymptomatic patients play in the transmission of COVID-19.

In theory, having the same amount of viral loads in nose and throat means asymptomatic carriers could spread the virus the same way as those who develop symptoms. However, people without symptoms are less likely to have a hacking cough that will spread infected droplets further into the air.  

While "there is as much virus in their respiratory mucus as someone who has the disease," it doesn't mean asymptomatic COVID-19 patients are spraying as much virus into the environment, said Dr Simon Clarke, a cellular microbiologist at the University of Reading. However, there still remains a risk from people without symptoms, he added.

The researchers said surveillance and isolation of asymptomatic patients may be required since the virus transmission by such patients may be a key factor in community transmission.  

"For a better understanding of the viral shedding and potential transmissibility of asymptomatic infection, large rigorous epidemiologic and experimental studies are needed," the researchers concluded.