A study published in the Annals of the American Thoracic Society has for the first time shown that SARS-CoV-2 RNA is present in the airborne particles even outside the rooms wherein infected persons were in home isolation.¹

A new study has detected tiny airborne particles containing RNA from the SARS-CoV-2 that cause COVID-19, both inside and outside of the rooms in which infected people were self-isolating at home.

The study participants were recruited in fall and winter of 2020–2021. Persons who tested positive for SARS-CoV-2 in the last one week were selected for the study. Saliva samples were tested at the first home visit to reconfirm their positive status. Eleven households were identified as eligible for the study. Two rooms were identified in each household for the study: an isolation room where the infected person was isolated and a separate but adjoining common room. Further, the participants were asked to record the amount of time spent in the isolation room and the common room.

Twenty air samples were collected from both isolation (n=11) and common rooms (n=9) to test for the presence of three SARS-CoV-2-specific genes in airborne particles by reverse-transcriptase polymerase chain reaction (RT-PCR) with cycle threshold (Ct) value < 37. The samplers were put farther from the vents, windows, traffic flow, and obstructing furniture and 1 meter away from the nearest wall. All samplers were placed in a facing down position to avoid droplets.

 

“For each of the three genes, the percentage of homes with a positive air sample ranged from 36% to 45% in the isolation room and from 22% to 67% in the common room”. Air samples from eight households (73%) out of the 11 included in the study were positive for at least one gene target, while samples from 5 out of 11 isolation room samples showed the presence of at least two genes.

 

At least one gene was detected in the common room of six of nine homes where sampling was done in both the isolation room and common room, while two genes were detected in four of these common rooms. “Seven of these nine homes reported no other cases in the household, including the two living alone”. 

 

In addition to the primary case, four out of the 11 households (36%) included also had persons with suspect or confirmed Covid-19 at the time of sample collection.

 

The time spent by eight out of the 11 (73%) Covid-positive patients in the common room ranged from a few hours to 14 hours, while five (45%) reported spending some time up to 8 hours, in other areas of the home. This shows that patients who were in isolation had not strictly complied with isolation guidelines.

 

This study has demonstrated the presence of airborne SARS-CoV2 RNA in indoor air of homes of most persons with Covid-19, not only from their isolation rooms, but also other rooms in the house. These findings possibly offer an explanation as to why there are family clusters of Covid-19 patients, particularly in crowded living conditions.

 

Respiratory viral infections mainly spread via droplets, which fall down and settle on surfaces or aerosols or droplet nuclei, which remain suspended in air for long periods of time.

Hand washing, face masks and physical distancing reduce the risk of infection from the larger droplets, while good ventilation, air filtration, along with better quality air masks, are prerequisites for protection against aerosols.

 

Hence, along with strict adherence to covid-appropriate behavior, it is now time to also focus on efforts to improve ventilation to improve indoor air quality as a measure to reduce spread of Covid-19. This can be done via opening windows and doors, or a window air conditioner with the vent control open. Exhaust fans also help and they should be functional. It is also important to maintain the room temperature between 24-30oC and relative humidity between 40-60%. All household members should wear a mask in shared closed spaces to reduce transmission risk in homes.

Reference

1. Laumbach RJ, et al. Presence of SARS-CoV-2 Aerosol in Residences of Adults with COVID-19. Ann Am Thorac Soc. 2022 Feb;19(2):338-341. doi: 10.1513/AnnalsATS.202107-847RL.