Monkeypox 2022 outbreak in non-endemic countries: Open questions relevant for public health, nonpharmacological intervention and literature review

Abstract

Starting from mid-May 2022, cases of human monkeypox started to rise in several non-endemic countries. By mid-July, more than 17000 confirmed/suspect cases have been reported by at least 82 countries worldwide, with a regular incremental trend. In order to contain the disease diffusion, risk evaluation is crucial to undertake informed decisions and effective communication campaigns. However, since orthopoxvirus infections so far have attracted low attention, due to the eradication of smallpox 40 years ago, and to the confinement of human monkeypox almost exclusively to endemic areas, several unresolved issues concerning natural history, ecology and pathogenesis remain. To this respect, we identified some open questions and reviewed the relevant literature on monkeypoxvirus and/or related orthopoxviruses. The results will be discussed in the perspective of their relevance to public health decisions, particularly those related to non-pharmacological interventions.

Keywords: animal reservoir; monkeypox; orthopoxvirus; prevention measures; seroepidemiology; spillover; subclinical infection; zoonosis.

Figure 1

Number of confirmed monkeypox cases. (A). Cumulative number of confirmed cases worldwide. (B). Number of newly reported confirmed cases per week, by continent/subcontinent. Source of original data https://www.monkeypox.global.health/, accessed on July 25, 2022.

Figure 2

Ecology of Monkeypoxvirus. (A) The virus is endemic in over 11 countries of Equatorial Africa, where its circulation is primarily maintained through spread among sylvatic animals, including primarily rodents such as rope squirrel, tree squirrel, Gambian pouched rat and dormice. Monkeys can also be infected. Occasional transmission to humans occurs from animals encountered during hunting, preparation and consumption of bush meat, forest exploration and agricultural activities. Human-to-human transmission is less frequent. (B) In non endemic countries, an outbreak of human MPX cases is currently going on, characterized by sustained human-to-human transmission, occurring through intimate contact with body (including genital) secretions, cutaneous lesions, respiratory droplets and contaminated fomites. Transmission from humans to sylvatic/peri-domestic rodents, or to domestic pets, has not been documented so far, but could represent a potential risk for MPXV endemization in the fauna of new countries outside of Africa. Created with BioRender.com.