Asymptomatic People Can Spread Coronavirus All Over Surfaces, Study Finds

People infected by the coronavirus which causes COVID-19 who don't show symptoms can still spread the germ to their surroundings, according to a study.

To conduct the research, scientists took over 100 samples from the air and surfaces of six negative pressure hospital rooms (meaning potentially contaminated air is preventing from escaping) housing 13 patients with the coronavirus, known as SARS-CoV-2 in the scientific community. The patients had returned to China from overseas and were staying at an isolation ward at a hospital in Chengdu, the capital of southwestern China's Sichuan province. Two of the patients were asymptomatic, and never developed COVID-19 symptoms.

Swabs were taken from the floor, bedrails, room and toilet door handles, light switches, foot flush buttons, sink rims, sink and toilet bowls and drains, bedside tables, bedsheets, pillows, equipment belts on walls, floors, and air exhaust outlets of their rooms.

Of the 112 samples they took, the team found 44 were contaminated with SARS-CoV-2. None of the air samples were contaminated.

A total of four surfaces—the bedrail, pillow, bedsheet, and air exhaust outlet—were contaminated in one asymptomatic patient's room. The findings show that such individuals can pose a risk to those with whom they are in close contact, the team wrote in their paper published in the journal mSphere.

It may therefore be safer for asymptomatic patients to stay at hospitals rather than in the home, the team said.

Charles Bangham, Professor of Immunology at the U.K.'s Imperial College London who did not work on the study, told Newsweek "this study is a salutary reminder that the contamination is widespread, and that the outflow air from the negative pressure room may also be contaminated."

The study was limited because the team didn't show if the virus was still viable, past studies have suggested the virus can deteriorate quickly on surfaces and has a low viability after a few hours, he said. Secondly, the method the team used to test for the coronavirus is vulnerable to false positives.

"It would be helpful to see results of these tests, carried out using the same procedures, in other rooms in the hospital in which the patients don't have SARS-CoV-2 infection," said Bangham.

Those who know or suspect they have come into contact with someone infected with SARS-CoV-2 should take the widely known precautions, said Bangham.

"The most important of these are to minimize contact with other people, especially the vulnerable; to wear a proper face covering when in proximity to others, and to wash hands thoroughly after known or potential contact with a contaminated object," he said.

Professor Daniel Altmann of the Department of Medicine at the U.K.'s Imperial College London, who also did not work on the study, told Newsweek the study "makes the point that, even with hand washing and sanitisers, [the] virus can be anywhere and everywhere."

Altmann said: "This study reminds us that asymptomatics can carry and spread virus just as well as symptomatics—quite a serious point to keep in mind."

The study comes after a World Health Organization infectious disease epidemiologist prompted confusion after suggesting it is rare for asymptomatic people to spread the virus. Dr. Maria Van Kerkhove later clarified there had been a misunderstanding between being asymptomatic and never showing symptoms despite being infected, and the pre-symptomatic—who have caught the virus but are yet to have symptoms.

There are a variety of reasons why some people never show the symptoms of COVID-19, Professor Brendan Wren, Dean of the Faculty of Infectious and Tropical Diseases at the London School of Hygiene and Tropical Medicine, told Newsweek in April.

For example, the individual may have gotten a low dose of the virus when they were infected, which may be more likely as people pay greater attention to their hygiene.

"Their overall immune system keeps it in check, and the individual has a sub [clinical]-infection, rather like a vaccine," he said.

Wren went on: "In addition, individuals are genetically different and some have a more efficient immune response to initially counteract the virus."

Experts from the University of Technology Sydney, the University of Sydney, and Sydney Children's Hospitals Network in Australia wrote in The Conversation that having a strong immune response when the viruses invades may prevent the infection from taking hold, reduce the quantity of the virus in the body, and prevent if from reaching the lungs.

This article has been updated with comment for Charles Bangham and Daniel Altmann.

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A stock image shows a woman in a kitchen. Scientists believe people with the coronavirus who don't show symptoms can contaminate their environment. Getty