People without symptoms have same amount of coronavirus in their bodies as those with signs of disease: Study
People infected with Covid-19, regardless of whether they show signs of the infection or not, have the same amount of virus in their bodies, suggests a new study. The finding indicates that isolating asymptomatic patients may help control the spread.
"Many individuals with SARS-CoV-2 infection remained asymptomatic for a prolonged period, and viral load [amount of virus] was similar to that in symptomatic patients. Therefore, isolation of infected persons should be performed regardless of symptoms," researchers from South Korea wrote in their study. The researchers know that people who show symptoms, including delayed ones, are more likely to drive the spread. As for asymptomatic patients, information on how the disease develops and the viral load is limited.
The current study fills these knowledge gaps. It also supports the theory that patients showing no signs of infection may also transmit the disease but offers no evidence to justify it. Further studies will have to evaluate if asymptomatic patients can pass on the infection to others. South Korea researchers studied 303 Covid-19 patients between March 6 and March 26, 2020. These participants — aged between 22-36 years — were isolated in a community treatment center in a city named Cheonan. Of them, 66.3% were women, and 3.9% of the patients had underlying health conditions such as hypertension, cancer and asthma.
Among the 303 isolated patients, 110 were asymptomatic at the start of the study and 21 eventually developed them. Patients showing delayed signs of infection are called presymptomatic. It took them an average of 15 days to develop symptoms, according to the study. As for the commonly reported symptoms, nearly 56% had a cough, 46% had nasal congestion, 28% had sputum production, 27% had a sore throat, 10% had an altered sense of smell, 5% had diarrhea, 4% reported a distortion in taste and 2% had abdominal pain.
The team of experts then collected samples from the nose, mouth and the mucus from the lower respiratory tract and analyzed the genetic material of the virus. The team also compared the amount of RNA between asymptomatic and symptomatic patients. Tests revealed that symptomatic and asymptomatic patients hold similar levels of the virus. But because symptomatic patients get more attention, countries could be underreporting infections. Isolating asymptomatic patients may help control the spread of the new coronavirus, the researchers suggested.
Ian Jones, professor of virology at the UK's University of Reading who was not involved in the study, told Newsweek: "All individuals were isolated and transmission was not tested so it is impossible to know if, generally, asymptomatics would transmit less virus to others, for example, because they do not cough or more as a result of freedom of movement." He added: "However, the study serves to reinforce the point that control of Covid-19 in the community requires regular widespread testing and that anyone positive should self-isolate whether they are symptomatic or not."
Daniel Davis, professor of immunology at the University of Manchester, told Newsweek that a "track and trace" system might not catch the infection in a significant number of people who do not show any symptoms. "However, this study didn't look at the transmission of the virus directly. It's hard to infer rates of transmission from the types of measurements done here," he said.
The study was published in JAMA Internal Medicine.