Viable monkeypox virus was found in almost all environmental samples from the patient’s room in the first week of infection

In a recent study published in medRxiv* Prepress server Researchers investigated the presence of viable monkeypox virus (MPXV) in a room occupied by an infected male patient admitted to the National Center for Infectious Diseases (NCID), Singapore.

Stady: Monkeypox virus is viable in a patient room environment. Image Credit: Marina Demidiuk / Shutterstock


MPXV continues to spread globally, with more than 16,000 MPXV cases and five deaths reported in 75 countries in five World Health Organization (WHO) regions. Subsequently, the World Health Organization declared the 2022 MPXV outbreak a global public health emergency. Studies have found that contact with wild animals in endemic areas (Semi-African tribes in forested areas) and close physical contact with infected individuals increases the risk of MPXV infection.

Epidemiological studies have shown that direct physical contact results in prolonged throat positivity for MPXV even after skin lesions have resolved, raising concerns about its aerosol-based transmission. However, there is a lack of data on patterns of MPXV transmission, especially systematic studies investigating human-to-human transmission of MPXV.

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In this study, researchers took longitudinal samples of air, surfaces, water, and dust in an airborne infection isolation (AIIR) room occupied by an MPXV patient who developed skin lesions and fever. The room was cleaned daily with 10,000 parts per million (ppm) bleach and had 12 HEPA filter changes per hour. The team performed environmental sampling on injury days 7, 8, 13 and 21. In addition, they performed air sampling on day 15 of injury using four NIOSH and two SASS samples.

The researchers used SASS and Coriolis samples for AIIR air sampling on days 7 and 8 of MPXV infection, with samples set at 0.8 and 0.9 m on the left and right sides of the patient, respectively. On days 13 and 21, the researchers placed an additional set of SASS and Coriolis air samples 2.5 meters from the patient. They placed all air samples on a cart about 1.2 meters off the ground. While the SAAS sampler operated for 2 hours at a flow rate of 300 L (l)/min, the Coriolis sampler worked at 100 L/min for 1.5 hours. Samples Particle samples (PM) with sizes PM1, PM 2.5, PM4 and PM 10 were collected in virus transfer medium (VTM).

The researchers collected all surface samples from the AIIR, including the room, toilet, and waiting room, using sterile nylon swabs pre-moistened with universal VTM. Furthermore, the team used sterile transparent stockings to collect dust samples from linen floors, the room, and toilets. They sent all study samples for testing to the Biosafety Level-3 (BSL-3) laboratory at the Institute of Environmental Health in Singapore. Finally, the researchers pre-processed these samples to extract MPXV deoxyribonucleic acid (DNA). They subjected viral DNA to quantitative real-time polymerase chain reaction (PCR) to estimate the number of viral copies. They cultured viruses for selected MPXV samples and observed a cytopathic effect (CPE).


The researchers detected MPXV DNA in the patient’s nasopharyngeal swab and perianal lesions on day 5 of infection when he was admitted to hospital. The frequency of skin lesions was highest in the buttocks, followed by the back and extremities (23 vs 15 vs four), but they disappeared eight days after injury. The patient was discharged from hospital on day 23 of infection with MPXV.

The team collected 179 environmental samples, of 56, 100, 16 and seven samples of air, surface, dust and water. Viral contamination in the air persisted for 21 days, and the peak viral load was 1.25 × 104 Copies/swab on the eighth day of air sampling. Dust samples had MPXV DNA up to day 21, with the highest viral load at day 7 in toilet floor dust samples, equivalent to 5.94 × 107 Copy / virus sample. It also fell to the lowest contamination level by day 21 of infection. The team noted that water samples collected from Sink P-traps were positive for MPXV DNA until day 13.


The researchers recovered viable MPXV in nearly all air samples from the patient’s room, although non-culturable, extensive surface contamination of the patient’s chair, toilet seat, and dust from bed linen in the first week of infection, with a gradual decrease subsequently. While detection of MPXV DNA across sampling days showed continued viral shedding throughout the course of the illness, recovery of viable virus from the chair and toilet seat correlated with the location of the skin lesions. Similarly, viable MPXV in surface and dust swabs indicates the potential for fomite-based transmission, especially in home settings.

Environmental contamination decreased from the second week of infection when the patient stopped developing new skin lesions. This discovery highlighted the importance of disinfecting chair and toilet surfaces and floors and taking precautions when handling linens. The researchers found MPXV only in particles with sizes greater than 4 micrometers, nullifying the possibility of MPXV transmission by breathing or, in this case, speaking. This could be due to 12 one-way air changes per hour of a HEPA filter or high ventilation rates. Therefore, future studies should examine direct breathing samples in the environment with typical atmospheric conditions in order to better understand the respiratory source of MPXV transmission.

However, the presence of live MPXV in the dust samples indicated pest infestation as a potential source of air pollution. The dose of the vaccine and the susceptibility of the host to a particular mode of transmission are likely to influence the transmission of all viruses. Therefore, future studies should evaluate the dynamics of MPXV transmission, including the infectious dose required to cause disease.

Previous studies suggested that pathogens capable of aerosol transmission should be associated with a high reproductive number (R .).0). However, whooping cough transmitted through droplets has a much higher R value0 It is a pathogen that causes tuberculosis transmitted by aerosols. Given this and the extraordinary abilities of MPXV to mutate, large-scale studies should evaluate all possible modes of MPXV transmission, especially in hospital settings, to mitigate its spread.

*Important note

medRxiv publishes preliminary scientific reports that are not subject to peer review, and therefore should not be considered conclusive, guide clinical practice/health-related behavior, or be treated as established information.