A study presenting evidence for the presence of SARS-CoV-2 RNA in the air is published in Nature today. Environmental monitoring of two hospitals and some public areas in Wuhan, China, reveals hotspots for airborne viral RNA, but whether this material has the potential to infect was not assessed. Although the sample sizes are small (fewer than 40 samples from 31 locations), the findings support notions that careful sanitization, good ventilation and avoidance of crowds can reduce the risk of airborne virus exposure.
Reported modes of SARS-CoV-2 RNA transmission to humans include close contact with infected individuals, contact with contaminated surfaces or inhalation of droplets released from the respiratory system of people with the virus. Whether there is further potential for SARS-CoV-2 to spread through the air has been less clear.
Ke Lan and colleagues set up aerosol traps in and around two government-designated hospitals for the treatment of patients with COVID-19 (the disease caused by SARS-CoV-2 infection) during February and March 2020. These sites included a grade-A tertiary hospital for patients with severe illness and a field hospital (a converted stadium) for patients with mild symptoms. The concentration in ventilated patient wards was generally very low, which the authors attribute to effective isolation and high air exchange. Patient toilets, which were not ventilated, had elevated concentrations of airborne viral RNA. The authors found that RNA was especially concentrated in areas used by medical staff to take off protective equipment, which suggests that virus-laden aerosols can become resuspended in the air when this equipment is removed. However, after increasing the rigour and frequency of sanitization efforts, no detectable evidence of airborne SARS-CoV-2 RNA was found in medical staff areas.
Concentrations of SARS-CoV-2 RNA in public areas outside the hospitals such as residential buildings and supermarkets, were generally low. However, two areas that were subject to large crowds passing through, including an outdoor space near to one of the hospitals, had elevated concentrations of SARS-CoV-2 RNA. The authors suggest that individuals infected with SARS-CoV-2 within these crowded areas may have contributed to the viral aerosols.
This study does not investigate whether the SARS-CoV-2 RNA has the potential to be infectious, and restricted access to the hospitals during the peak outbreak limited the number of samples that could be taken. Nonetheless, the study supports the use of thorough sterilization of the potential hotspots for virus-laden aerosols, well-ventilated hospitals and avoidance of crowds to reduce the risk of infection.
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