Mpox outbreaks chronology: From initial cases to WHO’s latest health emergency

Mpox, a viral disease first identified in 1958 and affecting mainly Central and West Africa, has shown a complex and evolving pattern of outbreaks (Image courtesy: https://www.who.int/)

The World Health Organization (WHO) has declared the escalating mpox outbreak in the Democratic Republic of the Congo (DRC) and several neighboring African countries a Public Health Emergency of International Concern (PHEIC). This declaration follows alarming reports of a significant surge in cases and the emergence of a new, rapidly spreading variant of the mpox virus, Clade 1b. Mpox viral disease has a long and complex history that highlights its evolving threat to public health.

Timeline of Mpox outbreaks

Early history and identification
1958: Mpox was first identified in Denmark when a pox-like disease outbreak occurred in a colony of macaques being kept for research. This initial identification led to the naming of the virus.

1970: The first human case of mpox was recorded in the Democratic Republic of the Congo (DRC) in a 9-month-old boy. This marked the beginning of the recognition of mpox as a human disease, particularly in regions where smallpox had recently been eliminated.

Spread in Africa

1970-2021: Over the decades following the first human case, mpox circulated increasingly within human populations in endemic areas of Central and West Africa. During this period, most cases were reported from rural, rainforest regions of the Congo Basin, particularly in the DRC. Human cases were also reported in 11 African countries, including Benin, Cameroon, the Central African Republic, Gabon, Côte d’Ivoire, Liberia, Nigeria, the Republic of the Congo, Sierra Leone, and South Sudan.

The disease generally spread through direct contact with wild animal species that carry the virus, including a range of rodents and primates, although the exact animal reservoir of the virus remains unknown. Human-to-human transmission occurred but was typically limited due to the requirement for close physical contact for the virus to spread.

Emergence of two distinct clades

Throughout this period, two distinct types of mpox were identified:

Congo Basin (Central African) Clade: Known to potentially cause more serious disease.
West African Clade: Typically associated with milder disease and a lower case fatality rate.

Outbreak in 2022 and the global spread

May 2022: An atypical outbreak of mpox was reported in the WHO European Region, where several Member States detected cases that were not linked to countries where the disease is endemic. This was the first time that a significant number of cases were reported outside of Africa.

July 23, 2022: As the outbreak expanded to include countries beyond the WHO European Region, the World Health Organization declared mpox a Public Health Emergency of International Concern (PHEIC).

Decline

Late 2022 - Early 2023: The outbreak began to subside significantly due to concerted action by governments, health authorities, and impacted communities. The majority of cases were identified among men who have sex with men (MSM), who sought care in sexual health clinics. Despite the decline in cases, WHO and health authorities emphasized the importance of avoiding complacency.

May 10, 2023: In recognition of the progress made in tackling the outbreak, the IHR Emergency Committee on mpox recommended lifting the PHEIC status. All cases detected during this outbreak were identified as the milder West African clade.

Ongoing outbreaks and emerging variants

2024: The DRC experienced a resurgence of mpox, with a significant surge in cases surpassing the totals from previous years. The situation worsened with the emergence of a new variant, Clade 1b, which spread primarily through sexual networks. This new variant has also been detected in neighboring countries, including Burundi, Kenya, Rwanda, and Uganda, raising concerns about its potential impact.

The DRC continues to face a high case fatality rate (CFR) for mpox, with the rate increasing from 4.5 percent in 2023 to 4.9 percent in 2024. The WHO declared the situation in the DRC and neighboring countries as a Public Health Emergency of International Concern (PHEIC) once again, highlighting the urgent need for a coordinated international response.

(Source: World Health Organization website)