SARS-CoV-2 lingers on in hospital rooms, toilets

Air samples of hospitals show frequent contamination with SARS-CoV-2 RNA, including toilets, staff areas, and the public hallways, a systematic review has found — suggesting that these areas deserve careful consideration for prevention of COVID-19 transmission. 

Nonetheless, these samples rarely contained viable viruses.

Among the 24 cross-sectional observational studies reviewed, 17.4 percent of the 471 air samples collected from close patient environments tested positive for SARS-CoV-2 RNA. [JAMA Netw Open 2020;doi:10.1001/jamanetworkopen.2020.33232]

In particular, the intensive care unit (ICU) settings were significantly more likely be contaminated than non-ICU settings (25.2 percent vs 10.7 percent; p<0.001). Moreover, the rate of positivity was regardless distance from patients (2.5 percent vs 5.5 percent for ≤1 m vs >1–5 m, respectively; p=0.22). 

“The concentration of SARS-CoV-2 RNA in aerosols detected in isolation wards and in areas where patients were receiving ventilation was very low,” the researchers noted. “[Of note,] the level of severity of patients’ infections was not associated with increased air contamination.”

“However, a higher concentration of viral RNA was found in patient toilets, public areas, and in some medical staff areas,” they reported.

When categorized according to hospital areas, the rate of contamination was highest in air samples of public hallways (33 percent), followed by toilets (33.3 percent), staff areas (12.3 percent), and clinical areas (8.3 percent).

“Toilets and staff rooms are often small and poorly ventilated … Toilet flushing may lead to the aerosolization of RNA in small and nonventilated toilets or bathrooms,” suggested the researchers.

In terms of distribution, SARS-CoV-2 RNA concentrations ranged from a median of 1 × 10³ copies/m³ in clinical areas to 9.7 × 10³ copies/m³ in the air of toilets/bathrooms.

In addition, concentrations per titre of SARS-CoV-2 were also high in protective equipment (PPE) removal and patient rooms, with mostly particles of <1 μm in size for PPE removal rooms and >4 μm in size for staff offices.

“As the World Health Organization recently acknowledged, airborne transmission could occur in crowded and closed environments in the community. This raises the question of whether similar transmission could occur in the hospital,” the researchers pointed out.

“The available data suggest that COVID-19 requires particular conditions to be transmitted through the air (such as AGPs*), leaning toward the effectiveness of surgical face masks in most circumstances,” they continued.

On the other hand, AGPs on the respiratory tract would call for respirators such as N95 or FFP2 to prevent SARS-CoV-2 from spreading and to protect healthcare workers, explained the researchers.

Nonetheless, among the five studies which attempted 81 viral cultures in total, only seven cultures (8.6 percent) were able to isolate viable virus from the air samples — all from close patient environments.  

“[These data] suggest that most samples did not contain enough infectious virus,” said the researchers.

However, they also noted that sampling methods — which could affect viral infectivity — varied widely across the studies. Hence, these points should be taken into account in future analysis for better comparability of data, they suggested.

*AGPs: Aerosol-generating procedures