Airborne transmission of COVID possible indoors: study

Closed-room experiments conducted by CSIR at three hospitals each in Hyderabad, Mohali; viral particles detected where COVID-positive persons spent longer periods

Airborne COVID-19 infection is definitely possible under certain conditions. Chances of picking up SARS-CoV-2 or the novel coronavirus from air is directly related to the number of positive cases in the room, their symptomatic status and duration of the exposure as proved in closed-room experiments conducted in three hospitals each in Hyderabad and Mohali (Punjab) by CSIR-Centre for Cellular & Molecular Biology (CCMB) and CSIR-Institute of Microbial Technology (IMTech).

In closed-room experiments, where one or more COVID-19 patients spent a short duration of time, one sample โ€” collected immediately after the departure of three symptomatic patients from the room โ€” was positive. The study, published in the preprint server medRxiv (yet to be peer reviewed), recommends demarcation of hospital areas into COVID and non-COVID areas to prevent cross infections.

But for asymptomatic cases, they showed the virus does not spread farther from them when they are seated in a room without perceived air flow due to a fan or AC. An air sampler was used to collect the virus particles, and then looked for their presence using RT-PCR.

โ€œWe have analysed 64 air samples collected from COVID and non-COVID areas of various hospitals and 17 samples from closed rooms occupied by COVID patients. Four samples from COVID care areas were positive for SARS-CoV-2 with no obvious predilection towards ICU/non-ICU areas,โ€ informed CCMB Director Rakesh Mishra on Tuesday.

The study shows early detection and isolation of positive individuals helps in preventing infection of other family members in a home setting too. Viral particles could be detected in air especially in closed rooms where COVID-positive individuals had spent longer periods, even after two hours of their exit from the room and at distances greater than two meters as well.

Social vaccines key

โ€œTill vaccines are available, social vaccine like wearing mask is the best prevention,โ€ said IMTech director Sanjeev Khosla.

โ€œThese findings show the coronavirus can stay in air for some time. But they also strengthen the importance of preventive guidelines like regular handwashing, using masks effectively and preventing symptomatic people from public mixing. Then, we can start getting back to normalcy more comfortably,โ€ said Dr. Mishra.

Considering the increased public mobility and interactions, wearing a mask in public should be made mandatory as it significantly decreases the viral load released by an infected individual. Spread of the pandemic, to a large extent, has been due to people having unprotected verbal interaction from close quarters with asymptomatic COVID-positive individuals. Risk of transmission is very low if both the affected and unaffected persons wear masks, he pointed out.

Social distancing is a must, and a distance of three feet at least, if not six feet, should be maintained. Spending more time in closed spaces can be risky even if social distancing is maintained as the virus can stay longer in poorly-ventilated rooms. Hence, it is also advisable to avoid going to othersโ€™ homes considering that the risk of contracting the disease in home environments is likely to be higher.

His advice is to conduct larger gatherings in open and well-ventilated spaces as it carries less risk of infection. Exposure to a COVID-positive individual for a short duration (less than 30 minutes) when adequate precautions are being taken does not significantly increase the risk of contracting the disease.

Short travel safer

The institute advisory is that short duration travel in metros/ local trains or buses is likely to be safe and for longer travel, the journey may be broken into parts to mitigate the risk. Masks should be used when using public toilets as flushing has potential to generate aerosols which can stay longer in air and the virus is known to be excreted in stool. If possible, the toilet should be reused only after half an hour or more of last usage while hand hygiene is a must.

Within offices, texting and e-mailing should be encouraged even if sitting next to each other in the same room instead of face-to-face interactions.

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