Mpox in Children and Adolescents

Résumé fourni par la source

Mpox is a zoonotic disease caused by the monkeypox virus (MPXV), a DNA virus of the Orthopoxvirus genus. First detected in humans in 1970 in the Democratic Republic of the Congo (DRC), mpox has historically been endemic to Central and West Africa, predominantly affecting children. Traditionally, 2 distinct clades of MPXV were recognized: clade I (formerly known as the Central African clade), associated with more severe disease, and clade II (the former West African clade), which causes milder disease.1 In 2022, a large multinational outbreak of MPXV was detected in nonendemic countries across Europe and the Americas,2 prompting the World Health Organization (WHO) to declare the outbreak a Public Health Emergency of International Concern. In contrast to earlier outbreaks, pediatric cases were rare and generally acquired through household contact or close contact with adult cases. Despite the increasing attention to mpox, data on its clinical presentation, disease burden, and optimal management in pediatric populations remain limited. In this article, experts collaborating on an international pediatric mpox registry under the VERDI consortium (https://verdiproject.org/) provide an up-to-date overview, with a focus on children and adolescents. We summarize the current epidemiology, clinical features, diagnostic approaches, treatment options and preventive strategies, including vaccination and infection control, while addressing the unique challenges posed by mpox in children and adolescents. EPIDEMIOLOGY MPXV was first identified in 1958 in a Danish laboratory during an outbreak among captive monkeys imported from Singapore. The first human case was reported in 1970 in a 9-month-old infant in the DRC.3 For decades, clades Ia and IIa were responsible for sporadic outbreaks in Central and West Africa, respectively, primarily following zoonotic transmission from infected animals, such as rodents or nonhuman primates, affecting mostly children. After 2010, the number of reported cases began to increase significantly, a trend that accelerated markedly in 2022 and 2023.4,5 Clade Ia has been associated with higher severity and mortality, with case fatality rates (CFR) reaching up to 12%, particularly among children under 5 years of age. In contrast, clade IIa has been linked to milder clinical courses, with CFR below 1%.1,3 Smallpox vaccination has shown cross-protection against mpox. Following the cessation of routine smallpox vaccination in the 1980s, population immunity declined markedly, particularly in younger generations, which has contributed to the reemergence and wider spread of mpox. In 2003, the first outbreak of mpox outside Africa was reported in the USA, caused by clade IIa.6,7 It was linked to imported rodents from Ghana that infected prairie dogs sold as pets. The outbreak affected 47 confirmed and probable cases, including several children who developed severe complications such as encephalitis and ocular involvement. No fatalities were reported. Nigeria experienced a substantial clade IIb outbreak in 2017, which subsequently became dominant over clade IIa.8 Some of these cases have been linked to international travel, resulting in imported infections to countries in nonendemic regions, such as the UK, Israel, Singapore and the USA between 2018 and 2021.4 A major epidemiological shift occurred in 2022, when the UK reported several mpox cases without travel links to endemic areas. Genomic analyses revealed that the causative strain belonged to clade IIb (lineage B.1), closely related to the strain circulating in Nigeria in 2017–2018 (lineage A). This led to an unprecedented global outbreak affecting over 110 countries, with more than 90,000 confirmed cases.2 The outbreak was primarily driven by sustained community transmission, particularly among men who have sex with men. Pediatric cases were rare, comprising less than 1% of global cases.9 The overall CFR was remarkably low (<0.1%), with severe disease mainly affecting immunocompromised individuals. During the 2022 international outbreak, exposure patterns varied by age group. Younger children were most commonly infected through direct skin-to-skin contact with caregivers or household members known to have mpox, whereas adolescents often acquired the infection through sexual contact—similar to adult transmission patterns.10,11 In contrast, outbreaks in African settings have demonstrated greater variability in transmission routes among children, including exposure to infected animals or skin-to-skin contact outside the household.12 Notably, acquisition in school settings during the 2022 outbreak appeared to be rare.13 In 2023–2024, a newly characterized clade Ib was identified in the DRC, demonstrating increased human adaptation and transmissibility, resulting in regional spread within Africa and travel-linked imported cases in countries such as France, Germany and Thailand.10,11 This resurgence prompted renewed global concern and led the WHO to declare mpox a Public Health Emergency of International Concern once again in August 2024. Historically, transmission in endemic countries primarily occurred through direct contact with infected animals, such as rodents or primates, or their bodily fluids. However, recent clades, Ib and IIb, harbor mutations that enhance MPXV adaptation to human hosts, enabling efficient and sustained human-to-human transmission through direct contact with an infected person’s lesions or body fluids, often in the absence of any zoonotic exposure. This has led to a sustained community transmission. Table 1 summarizes the characteristics of MPXV clades and lineages. TABLE 1. - Comparative Characteristics of Mpox Clades and Lineages Characteristic Clade Ia Clade Ib Clade IIa Clade IIb – Lineage A Clade IIb – Lineage B.1 Year identified 1970s 2023 1970s 2017 2022 Geographic distribution Central Africa (eg, DRC, CAR). Sporadic outbreaks DRC, spread to neighboring countries; isolated imported cases in Europe & Asia West Africa (eg, Nigeria, Ghana). Sporadic outbreaks (2003 USA) Nigerian 2017–19 outbreak Global outbreak (Europe, Americas, Asia) Main transmission route Zoonotic + limited human-to-human Sustained human-to-human (including community spread) + zoonotic Zoonotic Zoonotic and widespread human-to-human spread Human-to-human (primarily sexual contact) Age group affected Mostly children <15 years Children and young adults; moderate pediatric involvement Children and young adults Mostly adults; very few pediatric cases Adults (MSM); <1% children Clinical manifestations Severe systemic illness, rash, complications (eg, pneumonia, encephalitis) Fever, rash, lymphadenopathy, complications in children Milder generalized rash, limited complications Generalized rash, mild systemic symptoms Anogenital lesions, mild to moderate illness, low complication rate CFR 1–12%. Higher in children <5 years Scarce information. Suspected to be <1% <1% 3.6% (mostly in immunocompromised advanced HIV) <0.1% Stillbirth or miscarriage Reported Reported Insufficient data Insufficient data Not reported CAR, Central African Republic; CFR, case fatality rate; DRC, Democratic Republic of the Congo; MSM, men who have sex with men.Adapted from: Beiras CG et al. The Lancet. 2025;405:86–96.5 CLINICAL MANIFESTATIONS Mpox should be suspected in patients presenting with pox-like skin lesions and a history of known or potential exposure to MPXV, particularly if they have recently stayed in or traveled to areas with ongoing outbreaks.14 The incubation period typically ranges from 2 to 21 days. Classically, mpox presents with a prodromal phase lasting 1–5 days, characterized by fever, headache, asthenia, myalgia and lymphadenopathy, followed by the appearance of a vesiculopustular rash, resembling that of poxvirus infections. The rash typically progresses through successive stages—macules, papules, vesicles, pustules and crusts—over a period of 2–3 weeks.15,16 Risk of transmission persists until all lesions

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.