Look at strategies to manage Covid-19 spread in small spaces, say researchers

As few states witness an uptick in fresh Covid-19 cases, researchers suggest air surveillance as an effective means to measure the infection potential in closed spaces such as classrooms and meeting halls.

According to the researchers, based on the SARS-CoV-2 presence, containment measures can be confined to these smaller spots instead of implementing city, or residential area-wide restrictions.

As the Covid-19 pandemic moves into a third year, scientists are underscoring the need to refine strategies to control the spread of Covid-19, and other such infections.

A collaborative study by researchers from the Centre for Cellular and Molecular Biology (CCMB), Hyderabad, and Chandigarh-based CSIR - Institute of Microbial Technology (CSIR-IMTech)—in association with hospitals in the two cities—has quantified the airborne transmission of SARS-CoV-2.

More patients, stronger virus concentration

Researchers have found the positivity rate of presence of Covid-19 virus in air was 75 per cent when two or more patients were present in a room, as opposed to the 15.8 per cent rate when one or no patients were in a room.

For their study, CCMB and IMTech scientists analysed for the coronavirus genome content in air samples collected from different areas occupied by Covid-19 patients—such as hospitals, closed-rooms in which Covid-19 patients spent a brief period, and houses of home-quarantined patients.

The investigators found that the virus could be frequently detected in the air around Covid-19 patients, and the positivity rate increased with the number of patients present in the premises.

The SARS-CoV-2 virus was found in ICU as well as non-ICU sections of hospitals, suggesting Covid-19 patients dispersed the virus, irrespective of the severity of infection. The study also found viable coronavirus in air that could infect living cells, and that these viruses could spread over a long range of distance.

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“Our results show that coronavirus can stay in the air for some time in absence of ventilation in closed spaces. Our observations are concurrent with previous studies suggesting that the concentration of SARS-CoV-2 RNA is higher in indoor air as compared to outdoor air; and in indoor, it is higher in hospital and healthcare settings that host a larger number of Covid-19 patients, as compared to that in-community indoor settings,” said Dr Shivranjani Moharir, a scientist involved in the study.

Air surveillance needed

Dr Rakesh Mishra, lead scientist of the work and a Distinguished Emeritus Professor at CCMB, advocates air surveillance for viruses as the effective method ahead in Covid-19 control.

“Following our study models, we can develop air surveillance techniques that can measure the infection potential in public gathering areas such as classrooms, meeting halls. With these location-specific strategies in place, we can avoid blanket curbs such as lockdowns that have proven detrimental to the economy, livelihoods and children’s education,” Dr Mishra told DH.

To collect air samples from a room, a suction pump-like device was used for one or two hours, and the sample is examined for SARS-CoV-2, similar to that of an RT-PCR test.

“If, for example, a sample from a college classroom shows a high presence of virus particles, we can alert that particular room occupants and cancel the class for some time,” Dr Mishra explained.

“These air surveillance techniques are not just limited to coronavirus but can also be optimised to monitor other air-borne infections,” Dr Mishra, who is also the director of Tata Institute for Genetics and Society, said.

CCMB-IMTech scientists advise vaccination and wearing of face masks as the most effective method to contain the spread of Covid-19.