The gene of the complement-binding protein, an important anti-inflammatory factor of orthopoxviruses, is deleted from the genome of Western African strains of monkeypox virus

Monkeypox: A comprehensive review of a multifaceted virus

In May 2022, the world witnessed the re-emergence of the zoonotic disease monkeypox. While this was not the first epidemic of this disease, what differentiated the outbreak was the rapid global spread and increase of cases, which led the WHO to declare monkeypox a global health emergency. Although the disease spreads mainly through inadequately cooked meat of various rodent species, this virus also shows droplet, respiratory, sexual, and even vertical transmission. Monkeypox further multiplies in lymphoproliferative organs and presents with a classical smallpox-like rash, fever, headache, and muscle aches. Diagnosis is confirmed with a polymerase-chain-reaction test and is managed largely supportively with possible usage of some antivirals and immunoglobulins. Moreover, some pre-exposure and postexposure prophylactic vaccines have been developed. This paper aims to conduct an in-depth review of the historical epidemics, transmission, pathophysiology, clinical presentation, and management of the monkeypox disease.

Poxviruses and the evolution of host range and virulence

Poxviruses as a group can infect a large number of animals. However, at the level of individual viruses, even closely related poxviruses display highly diverse host ranges and virulence. For example, variola virus, the causative agent of smallpox, is human-specific and highly virulent only to humans, whereas related cowpox viruses naturally infect a broad spectrum of animals and only cause relatively mild disease in humans. The successful replication of poxviruses depends on their effective manipulation of the host antiviral responses, at the cellular-, tissue- and species-specific levels, which constitutes a molecular basis for differences in poxvirus host range and virulence. A number of poxvirus genes have been identified that possess host range function in experimental settings, and many of these host range genes target specific antiviral host pathways. Herein, we review the biology of poxviruses with a focus on host range, zoonotic infections, virulence, genomics and host range genes as well as the current knowledge about the function of poxvirus host range factors and how their interaction with the host innate immune system contributes to poxvirus host range and virulence. We further discuss the evolution of host range and virulence in poxviruses as well as host switches and potential poxvirus threats for human and animal health.

Human monkeypox: an emerging zoonotic disease

Zoonotic monkeypox virus is maintained in a large number of rodent and, to a lesser extent, nonhuman primate species in West and central Africa. Although monkeypox virus was discovered in 1958, the prototypic human cases were not witnessed until the early 1970s. Before this time, it is assumed that infections were masked by smallpox, which was then widely endemic. Nevertheless, since the 1970s, reported monkeypox virus infections of humans have escalated, as have outbreaks with reported human-to-human transmission. This increase is likely due to numerous factors, such as enhanced surveillance efforts, environmental degradation and human urbanization of areas where monkeypox virus is maintained in its animal reservoir(s) and, consequently, serve as a nidus for human infection. Furthermore, viral genetic predispositions enable monkeypox virus to infect many animal species, represented in expansive geographic ranges. Monkeypox virus was once restricted to specific regions of Africa, but its environ has expanded, in one case intercontinentally--suggesting that human monkeypox infections could continue to intensify. As a zoonotic agent, monkeypox virus is far less sensitive to typical eradication measures since it is maintained in wild-animal populations. Moreover, human vaccination is becoming a less viable option to control poxvirus infections in today's increasingly immunocompromised population, particularly with the emergence of HIV in Sub-Saharan Africa. An increased frequency of human monkeypox virus infections, especially in immunocompromised individuals, may permit monkeypox virus to evolve and maintain itself independently in human populations.