Mpox Testing Strategy, November 2024

1. BACKGROUND AND RATIONALE

Mpox is an emerging zoonotic disease caused by the mpox virus, a member of the Orthopoxvirus genus closely related to the variola virus that causes smallpox. Mpox was first discovered in 1958 when outbreaks of a pox-like disease occurred in monkeys kept for research. The first human case was recorded in 1970 in the Democratic Republic of the Congo (DRC) during a period of intensified effort to eliminate smallpox and since then the infection has been reported in a number of African countries. Mpox can spread in humans through close contact, usually skin-to-skin contact, including sexual contact, with an infected person or animal, as well as with materials contaminated with the virus such as clothing, beddings and towels, and respiratory droplets in prolonged face to face contact. People remain infectious from the onset of symptoms until all the lesions have scabbed and healed. The virus may spread from infected animals through handling infected meat or through bites or scratches. Diagnosis is confirmed by polymerase chain reaction (PCR) testing of material from a lesion for the virus’s DNA. Two separate clades of the mpox virus are currently circulating in Africa: Clade I, which includes subclades Ia and Ib, and Clade II, comprising subclades IIa and IIb. Clade Ia and Clade Ib have been associated with ongoing human-to-human transmission and are presently responsible for outbreaks in the Democratic Republic of the Congo (DRC), while Clade Ib is also contributing to outbreaks in Burundi and other countries.

In 2022‒2023 mpox caused a global outbreak in over 110 countries, most of which had no previous history of the disease, primarily driven by human-to-human transmission of clade II through sexual contact. In just over a year, over 90,000 cases and 150 deaths were reported to the WHO. For the second time since 2022, mpox has been declared a global health emergency as the virus spreads rapidly across the African continent. On 13 Aug 2024, Africa CDC declared the ongoing mpox outbreak a Public Health Emergency of Continental Security (PHECS), marking the first such declaration by the agency since its inception in 2017.7 This declaration empowered the Africa CDC to lead and coordinate responses to the mpox outbreak across affected African countries. On August 14, 2024, the WHO declared the resurgence of mpox a Public Health Emergency of International Concern (PHEIC) emphasizing the need for coordinated international response.

As of August 2024, Mpox has expanded beyond its traditional endemic regions, with new cases reported in countries including Sweden, Thailand, the Philippines, and Pakistan. Sweden has confirmed its first case of Clade 1 variant, which has been rapidly spreading in Africa, particularly in DRC. The emergence of this new variant raises concerns about its potential for higher lethality and transmission rates outside Africa.