Abstract and Introduction
Introduction
Monkeypox (mpox) is a zoonotic disease caused by Monkeypox virus (MPXV), an Orthopoxvirus; the wild mammalian reservoir species is not known. There are two genetic clades of MPXV: clade I and clade II (historically found in central and west Africa, respectively), with only Cameroon reporting both clades.[1] Human cases have historically been reported from 1) mostly rural, forested areas in some central and west African countries; 2) countries reporting cases related to population migration or travel of infected persons; and 3) exposure to imported infected mammals.[2] The annual number of cases in Africa has risen since 2014 and cumulatively surpassed reports from the previous 40 years for most countries. This reemergence of mpox might be due to a combination of environmental and ecological changes, animal or human movement, the cessation of routine smallpox vaccination since its eradication in 1980, improvements in disease detection and diagnosis, and genetic changes in the virus.[2] This report describes the epidemiology of mpox since 1970 and during 2018–2021, using data from national surveillance programs, World Health Organization (WHO) bulletins, and case reports, and addresses current diagnostic and treatment challenges in countries with endemic disease. During 2018–2021, human cases were recognized and confirmed in six African countries, with most detected in the Democratic Republic of the Congo (DRC) and Nigeria. The reemergence and increase in cases resulted in its being listed in 2019 as a priority disease for immediate and routine reporting through the Integrated Disease Surveillance and Response strategy in the WHO African region.* In eight instances, patients with mpox were identified in four countries outside of Africa after travel from Nigeria. Since 2018, introductory and intermediate training courses on prevention and control of mpox for public health and health care providers have been available online at OpenWHO.†,§ The global outbreak that began in May 2022¶ has further highlighted the need for improvements in laboratory-based surveillance and access to treatments and vaccines to prevent and contain the infection, including in areas of Africa with endemic mpox.
Annual mpox case and death counts during 2018–2021 were compiled from national surveillance data, WHO bulletins, and published case reports or outbreak investigations, and were verified with country surveillance teams; these data are presented with human mpox case report data since 1970. Since 2018, cases occurred in six African countries: Cameroon, Central African Republic (CAR), DRC, Nigeria, Republic of the Congo (ROC), and Sierra Leone (Table 1) (Figure). DRC reported >3,000 suspected cases per year, with a peak of 6,216 cases and 222 deaths in 2020. During 2018–2021, the number of confirmed mpox cases in CAR (79) from seven localities represented a notable increase compared with previous years, and an average of nine annual mpox outbreaks have occurred in CAR since 2018. In addition, nine cases were confirmed in Cameroon, where no human case of mpox had been documented since 1989; in a 2018 case, the virus shared genetic similarity with a clade II strain previously isolated from Nigeria,[1] and additional cases were reported in different regions of the country in 2020 and 2021. Two cases each in ROC and Sierra Leone were reported during 2018–2021.
Figure.
Reported confirmed human mpox cases — worldwide, 1970–2021
Source: World Health Organization as of December 6, 2022.
After 39 years without reports, Nigeria experienced a reemergence of cases caused by Clade II beginning in August 2017; this outbreak culminated in May 2018 with 122 confirmed or probable cases among 17 states and included seven deaths.[3] The country has continued to report mpox cases, with most concentrated in the southernmost states, including in urban settings since the outbreak period. In 2020, during the COVID-19 pandemic, the number of cases reported in Nigeria declined sharply (eight cases reported); however, case reports rose again in 2021. Nigeria has had a number of patients with MPXV and HIV coinfections, including four of the seven fatal cases in 2018. In addition, clinicians noticed atypical presentation that included lesions first appearing on the genitals and the absence of a febrile prodrome.[3,4] Five cases were reported in a prison in 2017, highlighting the need for infection prevention and control in high-density settings, such as correctional facilities and shelters, to prevent person-to-person transmission.[3]
During 2018–2021, eight independent travel-associated cases of mpox occurred outside Africa in persons traveling from Nigeria (Table 2). The patients were all men aged 30–50 years, and three reported that the rash first appeared in the groin area.[5–7] In one instance, secondary transmission resulted in an infection in a health care provider, and in another instance, in two family members. Each travel-associated case required public health resources to identify community contacts (including airline passengers in some cases) and health care contacts, and to establish care and treatment under strict infection prevention and control measures in health care and some residential environments.[6]
In 2021, WHO conducted a survey of orthopoxvirus testing capacity in 127 global laboratories. Among these, 78 (61%) reported working with orthopoxviruses for diagnostic (50), research (52), vaccine development (15), or manufacturing (four) purposes; and 38 (30%) worked with MPXV. Laboratories working with orthopoxviruses were present in the European (30 laboratories), Americas (21), African (11), Eastern Mediterranean (two), Southeast Asian (three), and Western Pacific (11) regions.
Morbidity and Mortality Weekly Report. 2023;72(3):68-72. © 2023 Centers for Disease Control and Prevention (CDC)
