Clinical manifestations and outcomes of human mpox infection from 1970 to 2023: A systematic literature review

Mpox is an important emerging infectious disease spreading rapidly with a changing geographical, clinical, epidemiological, virological, and clinical manifestations. The identification of clade I virus, the variant associated with severe disease and higher risk of death outside Africa in August 2024 is alarming. It is vital to document its changing epidemiology, clinical manifestations, and outcome to better understand how to prevent and treat the disease. We aimed to describe the clinical features and disease outcome of patients with mpox from 1970 to 2023. We performed a systematic search of peer-reviewed publications and grey literature using PubMed, MEDLINE, CINAHL, and EMBASE, published between 1973 and 2023. Thirty-seven articles met the inclusion criteria. We pooled data from 19 studies with at least 10 cases to enhance the appreciation of the review findings. A clear distinction was observed regarding the age, gender, sexual orientation, and HIV status distribution of mpox cases before and after May 2022. From May 2022 onwards, a high prevalence of mpox, almost exclusively, was observed among individuals identifying as men who have sex with men (MSM) 20–40 years with high-risk sexual behaviour and/or HIV immunosupression. No change in the common clinical manifestations – mucocutaneous rash, fever, lymphadenopathy, headache, and generalized malaise, typically during prodrome. However, certain symptoms such as myalgia/arthralgia, oropharyngitis, proctitis, and depression/anxiety were typically reported from May 2022 onwards. We could not establish from the review if the observed symptomatology change was real or resulting from an observation bias. Notably, a clear change in symptomatology was observed among individuals with immunosuppression who do not necessarily experience the prodromal stage and present with significantly more and larger mucocutaneous lesions that sometimes coalesced to form ulcers. Our pooled data report a CFR of 8.3 % before May 2022 and 1.2 % from May 2022 onwards. We show that mental health in patients with mpox has not received the attention required. There is a need for a strategic and strong approach to revamp mpox services to improve clinical suspicion and treatment, protect individuals most at risk including healthcare workers in high risk areas.