Presence of virus on surfaces may not mean it is infectious
A virus may be detectable on a surface days after a patient leaves behind traces, but this does not necessarily mean it is still infectious, experts say.
This is because most detection methods pick up the presence of the viral genetic material, which may linger for days even after the structure of the virus itself is broken.
An intact structure is needed for a virus to infect a host, such as a human, said Professor Wang Linfa, director of the emerging infectious diseases programme at Duke-NUS Medical School.
"Currently, the only way we can detect (the presence of the virus) is through its nucleic acid material, and this may or may not mean that we still have a live virus," he told The Straits Times. "This is why hygiene is very important, because disinfectants and soap can get rid of live viruses that are transmissible."
His points clarify a study by the United States Centres for Disease Control and Prevention (CDC), which was published earlier this week.
In the study, the CDC said the genetic material of the coronavirus could be detected on surfaces in the cabins of infected passengers on board a cruise ship for up to 17 days after cabins were vacated, but before disinfection procedures had been conducted.
Dr Michael Mina, a physician and assistant professor in immunology and infectious diseases at the Harvard T.H. Chan School of Public Health, remarked on Twitter that the CDC findings did not show the virus causing Covid-19 could survive for more than 17 days on a surface.
"(It just shows) that the viral RNA is detectable for at least 17 days," he said. "That's like saying that detecting DNA on a piece of hair post-mortem means a person is alive." Under a microscope, a coronavirus like the one causing the Covid-19 disease appears spherical, with a "crown" of spikes on its surface.
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