There has been a two-fold increase in the number of suspected mpox cases reported in the Democratic Republic of Congo so far this year as compared to 2020, which marked the year for the most reports of the virus, WHO has said.

Just as worrisome,  DRC has been the first country globally to see confirmed reports of sexual transmission of Clade 1 of the virus, which is known to be the most deadly with fatality rates as high as 10%. And the circle of mpox transmission more generally has expanded significantly, to include cases as far west as the capital Kinshasa and south Kivu in the eastern part of the country.

From 1 January to 12 DRC reported 12 569 suspected mpox cases, as compared to 6216 in 2020, the highest annual number previously reported.

“The reasons for this expansion, affecting men, women and children, remain unknown,” stated the WHO Disease Outbreak News, published Thursday.

Eleven of the 26 provinces of the Democratic Republic of the Congo are as endemic for mpox, but in recent years the number of provinces reporting mpox has been expanding, to 22 provinces as of November 2023, WHO stated.

Sexual transmission now reported in DRC of deadlier clade 1

Since 2022, an epidemic of the milder clade II of mpox has been ongoing globally, affecting many countries outside of Africa that had never reported mpox previously. “The spread of this epidemic was mainly driven by transmission via sexual contact among men who have sex with men,” WHO noted.

The first-ever globally confirmed case of sexual transmission of Clade 1 was reported in March. It involved a Belgium resident who tested positive for the virus during a visit to the DRC, where he had also had multiple sexual contacts at men’s clubs and elsewhere.

“Thereafter, sexual contacts of this case in the Democratic Republic of the Congo also tested positive for clade I MPXV [severe mpox infection], with closely related viral sequences. This is the first time that reported clade I MPXV infection is linked to sexual transmission within a cluster. Another outbreak in the country is also being reported with multiple cases of mpox among sex workers,” stated WHO.

In July, another case was reported in Kenge [Kwango province], involving a man who had sex with  men – and with apparently no links to the first cluster. Then in August, local transmission of the first severe mpox (MPXV) cases were confirmed in Kinshasa for the first time. Since then, some 102 suspected cases have been reported, two-thirds among men, and with a fatality rate for confirmed cases of 5.6%.

As of 22 November 2023, a total of 80 suspected and 34 confirmed cases of mpox (including 20 sex workers) of mpox have been reported in South Kivu – with no deaths. “Currently South Kivu province is grappling with conflict, displacement, food insecurity, and challenges in providing adequate humanitarian assistance, all of which have a profound impact on the local population, especially vulnerable groups, and might represent fertile ground for further spread of mpox.”

Patterns of transmission still porly understood

While human-to-human transmission of mpox through close contact has been reported since the 1970s, outbreaks were confined mostly to “small household or community outbreaks,” often around heavily forested areas and “presumed to be primarily due to zoonotic transmission.”

“These new features of sexual and unknown modes of transmission now raise additional concerns over the continuing rapid expansion of the outbreak in the country”  – and potential spread abroad, WHO stated, noting that the global outbreak of clade IIb mpox transmission between humans is ongoing in most WHO regions.

In addition, clade I mpox community outbreaks occur regularly in two other countries – Cameroon and the Central African Republic – as well as sporadically in others, including Sudan and South Sudan.

While transmission from animals to humans is also presumed to occur, the natural reservoir of the virus remains “unknown; while various small mammals such as squirrels and monkeys are known to be susceptible, they have rarely been linked to outbreaks,” WHO said.

Limited testing, few drugs and no immunization programmes

In terms of the risks of further sexual transmission, WHO note that “there are clubs in Kenge for men who have sex with men, some of whose members travel to visit other clubs within the country and outside the country, particularly in Europe and within Central Africa. In the city of Kinshasa, there are more than 50 such clubs. Some members of these clubs also reside outside the Democratic Republic of the Congo. This event is unusual and highlights the risk that MPXV clade I could also widely spread among sexual networks, as seen for clade II during the 2022-23 global outbreak.”

At the same time, DRC response capacities for mpox remains highly limited, WHO pointed out. “Surveillance and laboratory capacities remain suboptimal: only 9% (1106 / 12 569, as of week 44) of suspected cases this year have been tested by PCR. There are no immunization programmes for populations at risk of mpox in the Democratic Republic of the Congo outside of research projects.

Similarly, “access to the antiviral medication tecovirimat also remains limited to a few clinical research studies in the country.”

Following the 2022 declaration of the global mpox health emergency, involving clade II of the virus, developed countries launched an intensive vaccination campapign among groups at risk, to bring the epidemic under control. Indeed, WHO declared the global public health emergency to be over in May. 

However, the best-known mpox vaccine, MVA-BN, remains the monopoly of just one pharma company, Bavarian Nordic, which has demonstrated limited ability to rapidly expand production due to a manufacturing plant overhaul last year.

The manufacturer of TPOXX, the US based SIGA pharma company, pledged last year to make large quantities of the drug available for use by WHO and partners, including in developing countries.  The drug has been approved by the US Food and Drug Agency (FDA) and other regulators. However, major clinical trials on efficacy against severe mpox infection [MPXV] are yet to be undertaken, even though victims of severe forms of the virus are the most in need of supportive therapies, a group of Indian and Bangali researchers noted in a recent journal article, stating:

Mpox “only receives international attention when it spreads to high-income nations,” the researchers stated, noting that it is “thus becoming a risk to populations all over the world. There is an immediate and urgent need for conducting explorative researches to understand MPXV and the disease it causes (MPX), and develop effective and specific vaccines and antivirals.”

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