“The variant circulating in the DRC is dramatically deadlier than the one that swept the globe in 2022. About 6% of people who get this type of mpox are dying from it—compared to a 0.2% death rate for the 2022 strain. Most of the deaths in the DRC outbreak are among children.”
Melody Schreiber, American journalist and author
“We live in an interconnected world so the spread of this virus can continue to happen, and that is something that requires strong surveillance.”
Dr. Maria Van Kerkhove, infectious disease epidemiologist, World Health Organization
In July 2022, the World Health Organization (WHO) declared that a mpox epidemic was a global emergency and sounded its highest alarm declaring the epidemic a Public Health Emergency of International Concern (PHEIC). Lasting from July 2022 to May 2023, this PHEIC affected nearly 100,000 people (primarily gay and bisexual men) in 16 countries and killed about 200 people.
For the second time in less than three years, the WHO declared another mpox epidemic as a PHEIC on August 14, 2024. The current mpox epidemic is very concerning because it is caused by the novel clade Ib—a much more virulent mpox strain.
Given the global alarm set off by the clade Ib mpox virus, my aim in this week’s Germ Gems post is to refresh our memories about this tenacious pathogen and to highlight what’s needed to thwart its advancement around the globe. (Mpox was the subject of two previous Germ Gems posts, “Monkeypox arrives in the U.S.: Concern? Yes. Panic? No.,” May 25, 2022, and “Monkeypox: Now a Global Concern. What You Need to Know,” August 3, 2022.)
What is mpox? The mpox virus is an enveloped double-stranded DNA virus of the Orthopox genus, which includes variola (smallpox virus), cowpox, and other viruses. In 1958, researchers discovered the mpox virus in two outbreaks among research monkeys in Copenhagen, Denmark. (Mpox virus was previously known as monkypox but researchers now believe its natural hosts are small African rodents not monkeys, hence its renaming). In 1970, scientists recorded the first human case of mpox in the Democratic Republic of Congo (DRC) in a 9-month-old boy who was suspected of having smallpox.
Initial symptoms of mpox include fever, headache, body aches, fatigue, and swollen lymph nodes, followed by a skin rash with lesions that look like blisters, pus-filled bumps, or open sores. This viral disease is spread through: (1) direct contact with infected wild animals; (2) close contact (sexual or intimate) with a person with mpox; and (3) contact with contaminated materials like sheets, clothing and needles.
Mpox clade II caused the 2022 PHEIC. (The fatality rate for clade II is less than 0.2%.) At that time, spread of clade II mpox was recognized as a major threat primarily to men who have sex with men (MSM) and prevention efforts (behavioral modification and vaccination) were aimed primarily at this at risk group.
Mpox clade Ib is the cause of the current PHEIC. This novel clade Ib stain is not only more virulent than other clades of the virus but it is also more lethal (mortality of the clade Ib virus can reach 10%) and disproportionately affects children. (What’s different with the current clade Ib virus is detailed in the August 20, 2024 Journal of American Medical Association article, “The Resurgence of Mpox in Africa.”)
The DRC is again the epicenter of African cases of mpox, but the clade Ib mpox virus is also rapidly spreading throughout Africa, including at least four previously unaffected African countries (Burundi, Kenya, Rwanda, and Uganda). On August 16, the first case of the more contagious mpox clade Ib was detected outside of Africa—in Sweden in a traveler who recently returned from Africa. And on August 22, Thailand reported the first case of clade Ib mpox in Asia in a traveler returning from Africa.
A sizeable burden of clade Ib mpox cases are seen in children. For example, in the DRC, more than 50% of reported cases are in children younger than five years of age. It seems likely therefore that new modes of transmission are occurring such as, household contact and heterosexual contact. Moreover, young children, pregnant women, and immunocompromised people are at greatest risk of poor outcomes from the clade Ib mpox.
Clade Ib mpox virus in the U.S. According to Centers for Disease Control and Prevention (CDC), since 2022, the U.S. has had outbreaks of clade II mpox, mostly among MSM but also in some nonbinary and transgender people. (More than 32,000 people have been infected with clade II mpox in the U.S. and 58 have died). To date, no cases of clade Ib mpox have been reported in the U.S.; the CDC is, however, monitoring the European case.
Mpox, what’s next? Sadly, the National Institutes of Health (NIH) recently reported that a key drug—Tpoxx—is ineffective as treatment of the more lethal mpox clade Ib. But the good news is that a two-dose Food and Drug Administration-approved mpox vaccine provided by the company Bavarian Nordic is effective.
The WHO has issued an urgent call for more funding and supplies of mpox vaccine. On August 20, the United States Agency for International Development announced an additional $35 Million in emergency health assistance for the clade Ib mpox outbreak, and France announced that it would donate 100,000 vaccine doses.
Several authoritative sources, such as the WHO, the CDC, and the NIH, provide on-line updated information on the management of mpox. But what’s most urgently needed now to prevent the declaration of yet another (third) mpox PHEIC is “a coordinated international response,”—a point emphasized in a August 18, 2024 article in the Lancet. As the Lancet article concluded: “The increasing and altered character of mpox cases are not just a problem in the countries where they arise, or in Africa generally. They are a global threat to health that demands the attention and coordinated response of leaders everywhere, that is the message of a PHEIC, and one for which the international community must be held accountable.”
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