By Stan Deresinski, MD, FACP, FIDSA
Clinical Professor of Medicine, Stanford University
SYNOPSIS: A novel mpox clade has emerged in Africa and has the potential for a global epidemic.
SOURCE: AfricaCDC Centres for Disease Control and Prevention. Mpox situation in Africa. 30 July 2024. https://africacdc.org/news-item/mpox-situation-in-africa/
From the beginning of 2022 through July 28, 2024, 15 African Union Member States (AUMS) reported a total of 37,583 cases of mpox, among whom 1,451 patients (3.9%) were known to have died. There was a 78.5% increase in the number of new cases in 2023 when compared to 2022. Between the beginning of 2024 and July 28, 2024, 10 AUMS reported 14,250 cases (2,745 confirmed; 11,505 suspected), with 456 deaths (3.2%). This represents a 160% and 19% increase in the number of cases and deaths, respectively, in 2024 compared to the same period in 2023. The Democratic Republic of Congo (DRC) accounted for 13,791 cases (96.3%) as well as for 97% of deaths. Other member states reporting cases included Burundi, Cameroon, Central African Republic, Republic of Congo, Ghana, Liberia, Nigeria, Rwanda, Chad, and South Africa. On Aug. 13, 2024, the African CDC declared a public health emergency.
COMMENTARY
Prior to 2022, mpox cases generally resulted from spillover from zoonotic sources and were caused by one of two clades of the virus: clade I in the DRC and clade II in West Africa. Clade II generally caused relatively milder disease, while clade I was more severe and potentially lethal. In May 2022, a clade IIb variant, which is efficiently transmitted from person to person, most often during sexual contact, emerged to cause a global epidemic. To date, the number of documented cases in 116 countries has approached 100,000, with 184 deaths, and the clade I epidemic is continuing.
But evolution also continues. A new variant, clade Ib, has emerged in Africa and is the cause of the recent marked increase in the number of cases of mpox in the DRC and adjacent countries. Clade Ib appears to be more lethal than its clade Ia ancestor and is highly transmissible between humans, including by sexual contact. The dramatic increase in cases indicates the need for aggressive control measures. Among these necessary measures is widespread vaccination, but the worldwide supply of mpox vaccine is pathetically inadequate to the task.
At first, no clade I cases had been reported outside central and eastern Africa.1 But, as Shakespeare wrote in The Tempest, “What’s past is prologue.” Because of concern about spread from Africa, as occurred with the global clade II epidemic, the Centers for Disease Control and Prevention (CDC) recommends maintenance of a heightened index of suspicion in patients who recently have been in DRC or in adjacent countries (Republic of Congo, Angola, Zambia, Rwanda, Burundi, Uganda, South Sudan, or Central African Republic). On August 14, one day after the African CDC had done so, the World Health Organization declared mpox to represent a global public health emergency for the second time in two years. Then, on August 15, Sweden reported a case of clade I infection in a traveler from Africa.
The CDC recommends that all adults who have not had mpox but have sexual risk factors should receive mpox vaccination. This is especially important for those planning travel to countries with mpox transmission. There is no vaccination recommendation for travelers who do not meet current vaccine eligibility. Individuals who have been exposed to mpox are candidates for vaccination.
Of note is that on August 15, tecovirimat, the antiviral recommended for patients with mpox, was reported to have failed to improve the duration of lesions in adults and children with clade I infection in a clinical trial.2
REFERENCES
- Centers for Disease Control and Prevention. CDC Health Alert Network. Mpox caused by human-to-human transmission of monkeypox virus in the Democratic Republic of the Congo with spread to neighboring countries. Aug. 7, 2024. https://emergency.cdc.gov/han/2024/han00513.asp
- National Institutes of Health. News release. The antiviral tecovirimat is safe but did not improve clade I mpox resolution in Democratic Republic of the Congo. Aug. 15, 2024. https://www.nih.gov/news-events/news-releases/antiviral-tecovirimat-safe-did-not-improve-clade-i-mpox-resolution-democratic-republic-congo
