Asymptomatic COVID-19 carriers easily contaminate their surroundings, study shows

WASHINGTON — It doesn’t matter if you feel sick or you feel like a million bucks. Even asymptomatic COVID-19 patients can not only infect others directly, but also contaminate the surrounding environment. That’s the conclusion drawn from a new study using Chinese data.

The study’s authors say their findings emphasize the importance of hospitals properly cleaning all areas touched or inhabited by all COVID-19 patients.

“Placement of COVID-19 patients in rooms with negative pressure may bring a false feeling of safety and rigorous environment cleaning should be emphasized,” writes lead study author Zhiyong Zong, from the Department of Infection Control at West China Hospital.

Testing hospital rooms

It isn’t exactly breaking news that coronavirus patients can spread the virus to frequently touched items like clothes or furniture. However, this study focused more broadly on patients’ overall surroundings, a topic that’s understood far less extensively.

Researchers took samples from the surroundings and air within six negative pressure non-intensive care unit rooms that had been inhabited by 13 confirmed COVID-19 patients (two of those patients were asymptomatic). Areas and objects that were swabbed included bedrails, bedside tables, door handles, toilet handles, toilet bowls, and sinks. Additionally the research team checked bedsheets, pillows, floors, foot flush buttons, equipment belts on the walls, and air exhaust vents.

While all of the air samples ultimately came back negative, 44 out of 112 (39.3%) tested surface samples were indeed positive for the coronavirus.


“The SARS-CoV-2-positive rate also ranged from 16.7% to 53.9% for the individual sites,” the authors write. “Bedrails (53.9%), pillows (50.0%), bedsheets (50.0%), air exhaust outlets (50.0%), and light switches (40.0%) were the top five contaminated sites.”

Serious risks for asymptomatic COVID-19 patients

The authors say their study proves just how easily the virus can spread, even from asymptomatic people. For that reason, it may be wise to avoid even being in the same room or sharing items with others if you’ve been exposed.

“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,” the study reads. “In particular, in a single room with an asymptomatic patient, four sites including bedrail, pillow, bedsheet and the air exhaust outlet were SARS-CoV-2 positive. This highlights that asymptomatic COVID-19 patients can contaminate their surroundings and therefore make persons who have direct contact with them such as their family members and healthcare workers be exposed to SARS-CoV-2”

Most asymptomatic carriers will hopefully just want to stay home and avoid going out. But researchers say that even this approach puts people’s families and relatives in harm’s way. A safer option may be shelter hospitals.

“The findings also highlight that environmental cleaning should be emphasized,” the researchers note.

The study is published in mSphere.

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