Coronavirus could linger in ill-ventilated rooms and crowded spaces, may spread via aerosols: Study
Traces of the new coronavirus could linger in the air in rooms that lack ventilation or in crowded spaces, say researchers according to a new study.
The study investigated the aerodynamic nature of SARS-CoV-2 (the virus that causes COVID-19) by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the COVID-19 outbreak in February and March 2020. Researchers tested the concentration of SARS-CoV-2 RNA in aerosols — fine airborne particles — at the two hospitals. They found that traces of its genetic material were detectable in rooms, including an indoor space with a large crowd and toilet.
The presence of airborne viral RNA suggests that SARS-CoV-2 has the potential to spread through aerosols, says the research team from Wuhan University, China, and The Hong Kong University of Science and Technology, Hong Kong, China, among other institutes. They, however, did not analyze whether this material has the potential to infect others.
The team detected “elevated levels of viral RNA” in locations such as a small toilet used by patients, and staff changing rooms. No viral RNA was detected in staff rooms after they had been disinfected. Low to undetectable levels were found in the hospitals’ well-ventilated patient wards. Based on their findings, the team suggests that measures such as routine disinfection and better ventilation could help to control the virus’s spread.
“The concentration of SARS-CoV-2 RNA in aerosols detected in isolation wards and ventilated patient rooms was very low, but it was elevated in the patients’ toilet areas. Levels of airborne SARS-CoV-2 RNA in the majority of public areas was undetectable except in two areas prone to crowding, possibly due to infected carriers in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions showing peaks in submicrometre and/or super micrometer regions, but these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures,” say researchers in their findings published in Nature.
“Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted via aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of the aerosolized virus,” says the team.
The researchers set up 'aerosol traps' in and around two hospitals in the city. They sampled airborne SARS-CoV-2 and its aerosol deposition at 30 sites in two COVID-19 designated hospitals and public areas in Wuhan. “The two hospitals are exclusively used for COVID-19 patient treatment during the outbreak but each with unique characteristics serving different purposes,” says the team.
The Renmin Hospital of Wuhan University represents Grade-A tertiary hospitals designated for treatment of severe symptom COVID-19 patients, while the Wuchang Fangcang Field Hospital is representative of the make-shift field hospitals which was renovated from indoor sports facilities or exhibition centers to quarantine and treat patients with mild symptoms.
The sampling locations were classified into three categories according to their accessibility by different groups: patient areas such as intensive care units (ICU), coronary care units (CCU), wardrooms, toilet, and staff workstations; medical staff areas (exclusively accessed by the medical staff who had direct contact with the patients); and public areas or venues open for the general public.
The highest concentration inpatient areas was observed inside the Fangcang Hospital patient mobile toilet room. The results suggest overall low risks in the well ventilated or open public venues but do reinforce the importance of avoiding crowded gatherings and implementing early identification and diagnosis of infected carriers for quarantine or treatment, says the team.
“The findings from this study provide the first real-world investigation on the aerodynamic characteristics of airborne SARS-CoV-2 in Wuhan implemented with strict quarantine and travel restrictions during the peak of COVID-19 outbreak,” the findings state.
The mode of respiratory transmission of SARS-CoV-2 is not completely understood. A study at a hospital detected SARS-CoV-2 RNA in 35% of aerosol specimens from the intensive care unit and in 12.5% of specimens obtained from a COVID-19 ward. Another study from the University of Nebraska Medical Center demonstrated SARS-CoV-2 genome in 63.2% of air samples from rooms of 11 patients infected with COVID-19, with some samples obtained at distances more than 6 feet from the patient, and in 66.7% of 12 air samples obtained from hallways outside the patients’ rooms.
According to the World Health Organization (WHO), the disease spreads primarily from person to person through small droplets from the nose or mouth, which are expelled when a person with COVID-19 coughs, sneezes or speaks. “These droplets are relatively heavy, do not travel far and quickly sink to the ground. People can catch COVID-19 if they breathe in these droplets from a person infected with the virus. This is why it is important to stay at least 1 meter (3 feet) away from others,” say experts.
The WHO says that these droplets can land on objects and surfaces around the person such as tables, doorknobs, and handrails. People can become infected by touching these objects or surfaces, then touching their eyes, nose, or mouth. “This is why it is important to wash your hands regularly with soap and water or clean with alcohol-based hand rub,” says the agency.