Can monkeypox virus be transmitted through the air? – Correspondence

Dear Editor,

The first “monkeypox” outbreak was detected in the UK on May 7, 2022, and it spreads rapidly around the world. On July 23, WHO classified the monkeypox outbreak as a Public Health Emergency of International Concern (PHEIC). To date, more than 53000 cases have been reported in 103 countries worldwide (https://www.monkeypoxmeter.com/). Most case reports suggest that the primary route of transmission of monkeypox to be contact transmission and sexual transmission, particularly among gay men [1,2]. Does monkeypox also spread by droplet transmission, like smallpox, or even by airborne transmission? This are problems that deserve our attention.

Monkeypox is so similar to smallpox that some experts believe one can learn to study monkeypox from the way it spreads. The virologist Donald Milton noted that in the 1947 smallpox epidemic in New York, a smallpox patient infected another patient seven floors away through the hospital's internal circulation system, and that a German hospital had a case in 1970 in which a patient transmitted the virus to other patients three floors away.” Airborne transmission” seems to be the only plausible explanation for these outbreaks, and scientists observed in the 2017 monkeypox outbreak in Nigeria that 2 healthcare workers in the prison who did not have direct contact with the patient were eventually infected.

Recently, the Centers for Disease Control and Prevention (CDC) abruptly changed its guidelines for travelers to prevent monkeypox, including “wearing a mask,” saying that “wearing a mask can help you prevent many diseases, including monkeypox.” This advice sparked a debate - can the monkeypox virus be transmitted through air? Although this travel recommendation was quickly removed, citing the need to avoid “confusion” about a disease that is primarily transmitted through direct contact, the CDC still said that “household contacts and healthcare workers” should consider wearing masks in countries where monkeypox is transmitted. This guideline also applies to “close contacts of monkeypox patients."

Currently, the CDC website recommends in its monkeypox information sheet for healthcare professionals that “patients with monkeypox should wear a surgical mask, especially if they have respiratory symptoms (e.g., cough, shortness of breath, sore throat). If this is not feasible (e.g., a child with monkeypox), other family members should consider wearing a surgical mask when a person with monkeypox is present” [[3], [4], [5]].

The main route of transmission of smallpox virus is well-known to be airborne droplet transmission. Donald Milton [6] once noted that natural infection with smallpox is thought to occur through “large droplets” (droplets) deposited on the mucous membranes of the upper respiratory tract and that this natural infection through respiratory “large droplets” has a higher risk of viremia, rash symptoms, and death than that caused by dermal inoculation and nasal inhalation. If this theory holds true, then the primary natural route of transmission of smallpox is not contacted by transmission through the skin or mucous membranes, but airborne droplet transmission. It is important to note that the monkeypox virus can be transmitted through saliva, but this is not the same as airborne transmission. CDC also stated that there are significant differences between airborne transmission and transmission through respiratory secretions.

Evidence on whether the monkeypox virus can be airborne is still lacking. A study conducted by Verreault et al. [7] explored the aerosol transmission susceptibility of monkeypox virus. This study used a rotating chamber with a volume of 10.7 L in which monkeypox virus was used as an aerosolized and airborne virus to assess by incubation and quantitative polymerase chain reaction (qPCR) over a 90-hour period. Results showed that the virus concentrations detected by incubation analysis decreased by 2 Log10 during the first 18 hours, while virus concentrations detected by qPCR analysis decreased by 1 Log10. However, the virus concentrations remained stable from 18 to 90 hours, suggesting that the monkeypox virus has the potential to remain infectious in aerosols for more than 90 hours.

CDC's shift in attitude toward the need to wear a mask to prevent monkeypox is reminiscent of the early discussions about whether the new coronavirus is airborne. The agency did not acknowledge until May 2021 that the new coronavirus could be “suspended in the air for a few minutes to a few hours.” More research is still needed to uncover whether the monkeypox virus is also transmitted through different forms of respiratory transmissions, such as droplets, aerosols, and air, but until that is known, to be prepared is necessary.

Ethical approval

As no animal or human subjects are involved in this study, therefore not require any ethical approval.

Sources of funding

No specific grants from the institute or any public, commercial or not-for-profit sectors received to carry out this study.

Author contribution

Screening and Data extracting, NW,YZ; Writing, NW,YZ; Manuscript revision, NWand LW; Manuscript finalization: LW.

Trial register number

• 1.Name of the registry:
• 2.Unique Identifying number or registration ID:
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Guarantor

Lichun Wang, MD, West China Hospital of Sichuan University, 37 Guoxue Lane.

Chengdu, 610041, People's Republic of China.

Provenance and peer review

Not commissioned, internally peer-reviewed.

Data statement

The data and information in this correspondence article is freely available in public domain. Moreover, available data is not sensitive and not of a confidential nature.

Declaration of competing interest

None.

Declaration of competing interest

None.