The coronavirus could last on surfaces as long as 17 days, according to research on the disease-hit Diamond Princess cruise ship.
In a study published by US health officials, traces of the deadly infection were found on the deserted cabins more than two weeks after passengers evacuated the ship.
More than 700 passengers caught Covid-19 on the cruise ship.
Now a study suggests the virus is capable of sticking to surfaces for longer than originally thought.
The Grand Princess was quarantined off Japan.
Researchers, led by Takuya Yamagishi at the National Institute of Infectious Diseases, Japan, looked at the rooms of infected passengers aboard the Diamond Princess, including both those who showed symptoms and those who didn't.
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The findings have now been published in Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.
The authors wrote: "SARS-CoV-2 RNA was identified on a variety of surfaces in cabins of both symptomatic and asymptomatic infected passengers up to 17 days after cabins were vacated on the Diamond Princess but before disinfection procedures had been conducted.
"Although these data cannot be used to determine whether transmission occurred from contaminated surfaces, further study of fomite transmission of SARS-CoV-2 aboard cruise ships is warranted."
Health officials have warned repeatedly that people can catch the illness by touching a contaminated surface and then touching their face.
However, Dr Derek Gatherer, an infectious disease specialist at Lancaster University, is not convinced the coronavirus can stay on surfaces for 17 days.
He said: "For coronaviruses, it does seem excessive. I thought rotaviruses was the world record holders at about 14 days on some surfaces.
"I wonder if the tests are just picking up degraded virus products, which wouldn't be infectious."
Among 3,711 Diamond Princess passengers and crew, almost a fifth have had positive test results for Covid-19.
The CDC reported that passengers on the Diamond Princess mainly spread the virus before the ship went into quarantine. Nearly half didn't show symptoms when they tested positive.
• Covid19.govt.nz: The Government's official Covid-19 advisory website
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