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

Background Human monkeypox (MPXV) virus infection, an emerging zoonotic disease caused by an orthopoxvirus, leads to smallpox-like disease. Human MPXV infection was first reported in 1970 in the Democratic Republic of Congo (DRC). Before April 2022, MPXV cases were endemic and seldom reported outside African regions; but recent global outbreaks of MPXV are concerning. We aimed to investigate the epidemiology of emerging human monkeypox virus infection including the number of suspected, confirmed, and fatal cases as well as risk factors for contracting monkeypox infection. Design We performed a systematic review of peer-reviewed literature by following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. An electronic database search (PubMed, online Willey library, science direct) was undertaken. For monkeypox related studies, we included 25 peer-reviewed articles from 2018 and 2022 and data were extracted to inform current evidence on the cases and public health risk factors for developing infection, and public health advice. Results Our reports show a rapid rise of MPVX cases in highly endemic African regions after the 1970s, spread to other countries, and increased median age from young children to young adults. Cessation of smallpox vaccination might be one of the factors responsible for the findings. Till 2022 genomic sequences of ten MPXV strains, associated with the recent countrywide outbreak, have been determined. While West African Clade is mostly implicated in the recent viral surge, data were insufficient to determine which mutation contributed to increased transmissibility. In DRC, sleeping on the floor was significantly (odds ratio [OR] 6.1, 95% confidence interval [CI] 1.2-31.6) associated with contracting MPVX while eating or processing animal foods was not a significant risk factor. In the United States, cleaning cages, bedding sick animals (OR 5.3, 95% CI 1.4-20.7), or touching infected animals (OR 4.0, 95% CI 1.2-13.4), daily sick animal exposure (OR 4.0, 95% CI 1.2-13.4) were associated with contracting MPVX infection. Conclusion Recent global outbreaks, the rising incidence in young adults and endemic zones might result from smallpox vaccine cessation. Increased risk with sick animal exposure or sleeping on the floor suggests high infectivity from animal excretions. Increasing awareness, strict surveillance, and contact tracing can contain global outbreaks. Ring vaccination approach to exposed people can also be a strategy. Future studies should investigate to determine measures for rapid laboratory diagnosis, maintaining lab safety, and also transmissibility.