Asymptomatic Covid-19 patients also contaminate environment: Study

Both symptomatic and asymptomatic Covid-19 patients have the capability of contaminating their surroundings, according to a new study conducted in China.

The study, published in the journal mSphere, demonstrates the importance of environmental cleaning in areas occupied by patients with Covid-19.

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"Placement of Covid-19 patients in rooms with negative pressure may bring a false feeling of safety and rigorous environment cleaning should be emphasised," said study lead author Zhiyong Zong, from Sichuan University in China.

While it has been well recognised that SARS-CoV-2 that causes Covid-19 can be acquired by objects which are likely to carry infection, such as clothes and furniture, the contamination of patients' surroundings by the virus is largely unknown and understudied.

In the new study, researchers sampled the surroundings and the air of six negative pressure non-intensive care unit (ICU) rooms with 13 laboratory confirmed COVID-19 patients who had returned from overseas in a designated isolation ward in Chengdu, China.

The study cohort included 2 asymptomatic patients.

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Sampled sites included 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 wall, floor, air exhaust outlets and air.

The researchers found that 44 of 112 surface samples (39.3 per cent) were positive for SARS-Cov-2, detected by real-time polymerase chain reaction (PCR).

All of the air samples were negative, they said.

"The findings suggest that patient surroundings in this non-ICU negative pressure isolation ward for Covid-19 patients with mild disease or no symptoms were extensively contaminated by SARS-CoV-2," said Zong.

"In particular, in a single room with an asymptomatic patient, 4 sites including bedrail, pillow, bedsheet and the air exhaust outlet were SARS-CoV-2 positive," he said.

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This highlights that asymptomatic Covid-19 patients can contaminate their surroundings and therefore expose persons who have direct contact with them, such as their family members and healthcare workers, to SARS-CoV-2, the researchers said.

They said that isolation of asymptomatic Covid-19 patients at home impose risks to their family members, and that shelter hospitals may be a better option.