Air and surface sampling for monkeypox virus in a UK hospital: an observational study

Abstract

Background: An outbreak of monkeypox virus infections in non-endemic countries was recognised on May 12, 2022. As of September 29, more than 67 000 infections have been reported globally, with more than 3400 confirmed cases in the UK by September 26. Monkeypox virus is believed to be predominantly transmitted through direct contact with lesions or infected body fluids, with possible involvement of fomites and large respiratory droplets. A case of monkeypox in a health-care worker in the UK in 2018 was suspected to be due to virus exposure while changing bedding. We aimed to measure the extent of environmental contamination in the isolation rooms of patients with symptomatic monkeypox.

Methods: We investigated environmental contamination with monkeypox virus from infected patients admitted to isolation rooms at the Royal Free Hospital (London, UK) between May 24 and June 17, 2022. Surface swabs of high-touch areas in five isolation rooms, of the personal protective equipment (PPE) of health-care workers in doffing areas in three rooms, and from air samples collected before and during bedding changes in five rooms were analysed using quantitative PCR to assess monkeypox virus contamination levels. Virus isolation was performed to confirm presence of infectious virus in selected positive samples.

Findings: We identified widespread surface contamination (56 [93%] of 60 samples were positive) in occupied patient rooms (monkeypox DNA cycle threshold [Ct] values 24·7-37·4), on health-care worker PPE after use (Ct 26·1-35·6), and in PPE doffing areas (Ct 26·3-36·8). Of 20 air samples taken, five (25%) were positive. Three (75%) of four air samples collected before and during a bedding change in one patient's room were positive (Ct 32·7-36·2). Replication-competent virus was identified in two (50%) of four samples selected for viral isolation, including from air samples collected during bedding change.

Interpretation: These data show contamination in isolation facilities and potential for suspension of monkeypox virus into the air during specific activities. PPE contamination was observed after clinical contact and changing of bedding. Contamination of hard surfaces in doffing areas supports the importance of cleaning protocols, PPE use, and doffing procedures.

Funding: None.

Figure

Plan of room A representing the sites of samples and Ct values *Air samples were collected over a period of 10 min at a rate of 50 L/min (500 L total). Ct=quantitative PCR crossing threshold value of monkeypox DNA detected.