The Changing Global Epidemiology of Re-emerging Human Monkeypox Virus Infection: A Systematic Review

Human monkeypox virus (MPVX) infection represents an emerging zoonotic disease caused by an orthopoxvirus, resulting in a condition reminiscent of smallpox. More recent developments have witnessed a notable surge in global MPVX outbreaks, eliciting significant concerns. We aimed to investigate the epidemiological factors of the emerging human monkeypox virus infection, including the number of suspected, confirmed, and fatal cases, as well as the risk factors for contracting monkeypox infection. We performed a systematic review of peer-reviewed literature by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An electronic database search (PubMed, Wiley Online Library, and Science Direct) was undertaken. For monkeypox-related studies, we included 25 peer-reviewed articles from 2018 and 2022, and data were extracted on the current evidence on the cases and the risk factors for MPVX infection, to develop public health advisories. Our reports show a rapid rise of MPVX cases in the highly endemic African regions after the 1970s, spread to other countries, and an increase in the median age from young children to young adults. The cessation of smallpox vaccination might have been one of the factors responsible for these findings. As of 2022, the genomic sequences of ten MPVX strains associated with the recent countrywide outbreak have been determined. While the West African Clade has been primarily implicated in the recent viral surge, data were insufficient to determine which mutation contributed to increased transmissibility. In the Democratic Republic of the Congo (DRC), sleeping on the floor was significantly associated with contracting MPVX, while eating or processing of animal foods was not a significant risk factor. In the United States, cleaning the cages and bedding of sick animals, touching infected animals, and daily exposure to sick animals were associated with an increased probability of contracting the MPVX infection. Recent global outbreaks and the rising incidence of MPVX infections among young adults in the endemic zones might be a result of the cessation of the smallpox vaccine. The increased risk associated with exposure to sick animals or sleeping on the floor suggests high infectivity from animal excretions. Increasing awareness, strict surveillance, and contact tracing can help contain global outbreaks. The ring vaccination approach for exposed individuals is another potential disease containment strategy. Future studies should investigate measures for rapid laboratory diagnosis, maintaining lab safety, and transmissibility.