Air detection of monkeypox virus in a dedicated outpatient clinic room for monkeypox infection diagnosis

Abstract

Background

The World Health Organization (WHO) reported an outbreak of monkeypox virus (MPXV) in Western countries on May 12^th, 2022. In early October, WHO counted 68 900 cases in the world outside Africa. MPXV spreads all around the environment of infected patients through direct contact with lesions, body secretion, or liquids. Interrogations about MPXV spreading through respiratory secretions have been reported but appear bewildering. Thus, we investigated for virus identification in the air around infected patients to move forward with unresolved questions.

Methods

We collected air samples using the AerosolSense™ device in a dedicated room where monkeypox suspected patients were examined in our quaternary hospital's outpatient infectious disease clinic. Samples were analyzed with a MPXV PCR to determine the presence of viral DNA in the air.

Results

The study took place from July 26^th to August 5^th, 2022. We obtained seven four-hours-bioaerosol samples during the study period. Over the seven sessions sampled, six air samples were positive with a median Ct value of 36 (min-max: 32.0 – 38.0). Forty patients were present during the investigation; 17 (43%) were diagnosed monkeypox positive; 13 clinically and four virologically with a median Ct of 21 (min-max: 18.0 – 35.0). During the session, where no patients were diagnosed with monkeypox, air collection was also MPXV negative.

Conclusion

This investigation reports the presence of MPXV DNA in air samples collected in a room dedicated to monkeypox-infected patients' examination and testing. Thus, we highlight the importance of personal protective equipment worn by consulting patients and healthcare workers and surface decontamination to avoid infection transmission.

Dear Editor,

We read with interest the article by Raccagni et al. reporting, in the context of the recent worldwide outbreak,^{1 , 2 , 3} monkeypox virus (MPXV) infection occurred among individuals who got the smallpox shot. Healthcare workers (HCWs) are eligible for smallpox vaccination to prevent infection.⁴ In addition, to protect them from an occupational disease, Personal Protective Equipment (PPE) is required, mainly to avoid MPXV infection. MPXV is transmitted by direct contact with wounded skin or mucous membranes of a person with a monkeypox infection. The virus might also spread through large respiratory droplets, from mucus or saliva, during close face-to-face contact. Previous studies of monkeypox outbreaks show that spreading MPXV through respiratory secretions is unlikely.⁵

However, a MPXV transmission from a patient to a healthcare worker in the United Kingdom has been reported; authors hypothesized that transmission probably occurred through contact with contaminated bedding of a monkeypox-confirmed patient who presented active skin lesions.⁶

In this study, we investigated whether the MPXV could be detected from air sampling in the consultation room of the monkeypox diagnostic center set up within the Infectious Diseases department of Saint-Louis Hospital, Paris, France.

The investigation was carried out in a 130 ft² consultation room. This space benefits from one large window that can be opened, allowing fresh air to come in. In addition, a ventilation system ensures air renewal through several vents allowing air to pass in/out for blowing and aspiration. Bio cleaning was performed between each consultation.

One AerosolSense™ sampler (ThermoFisher Scientific™) was set in the room and settled 100 cm above the floor on a dedicated surface, as depicted in Fig 1 . The sampler collects air thanks to an omnidirectional sampling head at a rate of 200 L/minute. A collection substrate is in a sample cartridge inside the sampler. The air sample is sent to the collection substrate through an accelerated slot impactor. Air is drawn through the sampler and particles are trapped on the collection substrate. After the sampling cycle, the sample cartridge was removed and sent to the Virology laboratory for PCR testing. Particles were eluted by squeezing the sample cartridge sponge in a tube containing 2 ml of phosphate buffer saline. After a heat inactivation step of clinical and air samples (12 minutes at 70°C), nucleic acids were extracted using MagNA Pure LC 2.0 Instrument (Roche, Meylan, France). MPXV-specific real-time polymerase chain reaction (PCR) assay was performed on an ABI 7500 Real-Time PCR System (Thermo Fisher Scientific™, Waltham, MA) as described previously. ⁷ Results of MPXV detection were reported with cycle threshold (Ct) values. Results with Ct values higher than 40 were considered negative.

Fig. 1.

Outpatient clinic with the AerosolSense™ sampler.

We performed air and patients sampling during seven days, from July 26^th to August 5^th, 2022. The air sampling took place continuously, during sessions of four hours each day. Patient samples (oropharyngeal, skin, or genital) were collected during the consultation if the clinical diagnosis of monkeypox was not obvious clinically.

HCWs wore PPE composed of N95 Filtering Facepiece Respirators while consulting patients in the MPXV dedicated room. In addition, patients were required to wear surgical masks, except during oropharyngeal sampling. Finally, patients and HCWs had to perform hand hygiene before and after each consultation.

Patients’ characteristics and results are presented in Table 1 . Seven bioaerosol samples were taken during the study period. Throughout the sampling periods, 40 patients visited the clinic for suspected MPXV infection, and five different HCWs took care of these patients as medical assistants, nurses, and physicians.

Table 1.

Patients' characteristics, clinical and virological Monkeypox virus status. Air samples were taken during a four-hour period that the patients were in the examination room.

Date	Patient number	Sex	Age	MPXV infection	Type of diagnosis	Type of samples tested	MPXV PCR Result	MPXV PCR Ct value	Air sampler result	Air PCR MPXV Ct value
July 26th	1	M	32	no	-	oropharyngeal	negative		positive	35
	2	M	54	no	-	-	-
	3	M	36	yes	clinical	-	-
	4	M	39	yes	clinical	-	-
	5	M	44	no	-	-	-
	6	M	31	no	-	skin lesion	negative
	7	M	36	no	-	-	-
	8	M	35	yes	clinical	-	-
July 27th	9	M	35	yes	virological	oropharyngeal	positive	35	positive	35
	10	M	29	no	-	skin lesion	negative
	11	M	30	no	-	skin lesion	negative
	12	M	34	no	-	skin lesion	negative
	13	M	34	yes	clinical	-	-
	14	M	34	yes	clinical	-	-
	15	M	49	no		skin lesion	negative
July 29th	16	M	34	yes	clinical	-	-		positive	38
	17	M	41	yes	clinical	-	-
	18	M	45	no	-	skin lesion	negative
	19	M	37	no	-	-	-
	20	F	45	no	-	skin lesion	negative
August 1st	21	M	33	yes	clinical	-	-		positive	32
	22	M	38	no	-	skin lesion	negative
	23	F	19	no	-	vulva lesion	negative
	24	M	40	no	-	skin lesion	negative
	25	M	25	yes	clinical	-	-
	26	M	22	yes	clinical	-	-
	27	M	54	yes	virological	penis lesion	positive	18
	28	M	29	yes	virological	skin lesion	positive	21
August 3rd	29	M	28	yes	virological	oropharyngeal	positive	20	positive	37
	29	M	28	yes	virological	anal lesion	positive	22
	30	M	35	yes	clinical	-	-
	31	M	51	no	-	skin lesion	negative
	32	M	41	no	-	skin lesion	negative
August 4th	33	F	25	no	-	skin lesion	negative		positive	37
	34	M	44	yes	clinical	-	-
	35	M	24	yes	clinical	-	-
	36	M	32	-	-	-	-
	37	M	28	no	-	skin lesion	negative
August 5th	38	F	33	no	-	-	-		negative	-
	39	M	37	no	-	-	-
	40	M	34	no	-	-	-

Over the seven sampled sessions, six samples were positive with a median Ct value of 36 (min-max: 32.0 – 38.0). Of the forty patients examined; 17 (43%) were diagnosed monkeypox-positive; 13 clinically and four virologically with a median Ct of 21 (min-max: 18.0 – 35.0). One session sampled did not show the presence of MPXV in the bioaerosol, corresponding to the only session during which no patients were diagnosed with monkeypox.

Neither HCWs nor monkeypox-negative consulting patients reported MPXV symptoms during the study period or within the following 21 days.

Thus, we report the presence of viral DNA in the air, although patients wore surgical masks, reinforcing the importance of the HCWs being suitably protected, and wearing N95-type masks.

MPXV can spread in the immediate environment of infected people.⁸ Medical literature reports a case of human-to-human transmission of MPXV through contact with contaminated bedding⁶ questioning the possibility of MPXV airborne transmission, even though no such transmission route has been reported during the current outbreak. A recent publication reported evidence of MPXV infectious particles in hospitalized patients' rooms on surfaces and one air sample in the PPE doffing area.⁹

Even though we identified the presence of MPXV particles among air samples, we cannot confirm if they were infectious or not. However, no HCWs in contact with these patients declared monkeypox symptoms during the 21 days following exposure. Of note, HCWs all wore PPE, including N95 Filtering Facepiece Respirators, gloves, and protective glasses and performed hand hygiene before and after care. In addition, we noticed that no monkeypox-negative patients, examined on the days during positive air samples, were found to have contracted MPXV infection although they only wore surgical masks. Additional studies could be performed with cultures of MPXV from air samples with high viral loads to determine its ability to be infectious.

To our knowledge, we report the first air sampling taking place in an outpatient consultation room in a quaternary healthcare facility receiving patients with suspected monkeypox infection. The viral particles detected could have been spread through the air from the skin, genital or oropharyngeal lesions, or respiratory secretions.

The presence of viral fragments identified in bioaerosols suggests that greater attention should be paid to the possibility of a respiratory human-to-human transmission, to avoid HCWs infection or hospital-acquired infection, especially for immunocompromised patients who are numerous in a quaternary healthcare facility.