People infected with the coronavirus disease or COVID-19 may have the same amount of virus in the body, regardless of whether they show symptoms or not, according to a small Chinese study.
One patient, who happened to be in close contact with a confirmed infected patient, did not show any signs of the disease. However, when doctors tested him, they found the virus hiding in his throat and nose — astonishingly, at levels normally found in those with symptoms.
This new study makes the case that asymptomatic patients, those showing no symptoms, are capable of infecting others. "These findings are in concordance with reports that transmission may occur early in the course of infection," the team wrote in their report.
"If confirmed, this is very important," Dr Gregory Poland, a virologist and vaccine researcher with the Mayo Clinic in Rochester, Minnesota, who was not involved with the study, told Reuters.
People infected with COVID-19 show symptoms such as fever, cough, and shortness of breath, according to the Centers for Disease Control and Prevention (CDC).
The study included 18 patients, including nine men and nine women aged between 26 and 76, from South China's Guangdong Province. Of the 18 patients, 14 had traveled to Wuhan in January.
On the whole, the team collected 72 nasal swabs and 72 throat swabs for the study. In them, they checked for the amount of virus in the body or viral load.
Among 17 patients who showed symptoms, the experts found high levels of viral load soon after symptoms showed up, detecting higher amounts in the nose than in the throat.
Doctors suspected that the 18th person, who had close ties to a coronavirus positive patient, might also have the COVID-19. Though the man looked perfectly fine, he ended up testing positive on days 7, 10, and 11 after contact.
"The viral load that was detected in the asymptomatic patient was similar to that in the symptomatic patients," wrote the study's authors.
SARS control strategies may not work for COVID-19
By studying the patterns of infection among participants of the study, the team believes that the new coronavirus spreads more like the flu than its closest relative, SARS.
The findings add to evidence that this new virus, though genetically similar, is not behaving like SARS, Kristian Andersen, an immunologist at Scripps Research in La Jolla, who was not involved in the study, told Reuters.
"This virus is much more capable of spreading between humans than any other novel coronavirus we've ever seen. This is more akin to the spread of flu," he added.
This means that strategies that succeeded in halting the SARS outbreak may not work against COVID- 19. To control the 2002-2003 SARS epidemic, health authorities kept the virus from spreading by quickly identifying infected individuals and isolating them for treatment before they infect others.
The authors "suggest that case detection and isolation may require strategies different from those required for the control of the SARS virus." The study has been published in the New England Journal of Medicine.