Mpox is mutating to become more contagious in Africa, alarming some health experts

Public health officials are concerned about a new strain of mpox (formerly called “monkeypox”) that could be spreading more easily between humans. The infectious viral disease, which is related to smallpox, causes a distinct rash of lesions and bumps and can sometimes be fatal.

In late June, health authorities first rang alarm bells over a strain of mpox spreading through the Democratic Republic of Congo. Specifically, the new strain has been circulating in the North and South Kivu provinces of Congo. Scientists believe it mutated from the lineage called clade I that impacted the U.S. and other Western countries between 2022 and 2023. "There is a critical need to address the recent surge in mpox cases in Africa," Rosamund Lewis, the World Health Organization’s (WHO) technical lead for mpox said in a media briefing.

Less than two weeks later, on July 11, the WHO reiterated that mpox remained a global health threat, with 26 countries reporting cases to the agency in July. This year, there have been more than 11,000 cases reported, and 445 deaths, with children the most affected in the Democratic Republic of the Congo. According to WHO, South Africa has also recently reported 20 cases of mpox — including three deaths, the first cases reported in South Africa since 2022. WHO said all of the cases were men, and most self-identified as men who have sex with men. None had reported cases of international travel, which suggested that community transmission is ongoing.

In a media briefing, Dr. Michael Ryan, Executive Director of WHO's Health Emergencies Programme, said it was a concern that public health officials don’t have “a complete understanding of the dynamics of community transmission at this time in the likes of Congo.”

“We're always worried about a disease crossing a border — be it in Africa or around the world — and we saw how mpox spread quite rapidly around the world in the previous event,” Ryan said, referring to 2022. “But also what I would say in relation to that previous event was how certainly impressed I was with the way in which governments reacted — but more importantly the way in which the communities affected reacted.”

Mpox first originated in wild animals in the jungles of west and central Africa. On occasion, it has made the jump to humans. The first known human case of mpox was detected in 1970 in a 9-year-old boy in a remote part of Congo. According to the CDC, mpox can cause symptoms like painful rashes that can appear all over a person's body. The other symptoms are similar to influenza, and include swollen lymph nodes, muscle aches, backaches, headaches, fever, fatigue and chills. Eventually, lesions form and progress through several stages before falling off.

"The lesions in my sensitive areas and underwear zone became really painful to the point where I couldn't sleep," 30-year-old Matt Ford explained to Self magazine in 2022. "I'd describe the sensation as a dull, chronic pain that became jolts of intense pain if I moved the wrong way; I am not sure I've experienced anything quite like it."

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Notably, mpox spreads through direct contact with body fluids or sores on the body of someone who has mpox. It can also spread through materials that have touched body fluids or sores that have been in contact with someone who's infected — for example, clothing or bedsheets. It can spread through respiratory droplets when people have close face-to-face contact. Before the new strain, experts said this was not the main mode of transmission. According to data from the WHO, 91.4 percent of cases have been linked to sexual contact.

But now the new strain appears to spreading more easily between humans, raising questions about its mode of transmission.

“It’s a phenomenon,” William Schaffner, a professor of infectious disease at Vanderbilt University Medical Center, told Salon. “And the thought is that somehow, because of its rapid spread in the Congo, it may have acquired an enhanced transmissibility genetic component fairly recently.”

But the exact science behind it remains unclear and more research needs to be done. Amesh Adalja, an infectious disease expert and senior scholar at Johns Hopkins University Center for Health Security, told Salon in a phone interview that the new strain appears to have additional mutations that make it more transmissible between humans.

“It appears that the clade I virus has evolved to another subform. We call it clade 1b and that clade of the virus seems to have additional mutations in it that may make it more efficiently spreading than other versions of mpox between person to person,” Adalja said. “And the concern is that makes it harder to control, because it's spreading with greater ease, and there's some suggestion of increased severity.”

However, Adalja emphasized in the bigger picture, this doesn’t affect the efficacy of vaccines or antivirals. Indeed, there are vaccines for monkeypox. As Salon previously reported, in 2022, the U.S. released the Jynneos vaccine against monkeypox from the Strategic National Stockpile, but supply was limited. Moreover, those who received the smallpox vaccine before it stopped being regularly given in the 1970s will likely have protection against mpox.

There are always ways to test for it. In a media statement, the CDC said “viral sequencing from this cluster is reported to contain a deletion in a specific part of the genome that might impact how well the CDC clade I PCR test works.” However, they said the FDA-cleared CDC non-variola orthopoxvirus (NVO) PCR test and additional PCR tests that target other viral genes will still be able to detect the virus. Since the mode of transmission isn’t airborne, Adalja said he’s not so worried about mpox and doesn’t believe mpox has “pandemic potential” in the United States.

“I don't think a virus that spreads through contact has the ability to cause a pandemic,” he said. “Bodily contact, skin-to-skin contact is constraining for any type of pathogen — when something can spread through the air, it's difficult to do anything about it, as we saw during COVID-19.”

However, both experts agreed that the humanitarian crisis in the Congo needs to be contained.

“From a humanitarian point of view, we are very concerned about the patients that are being affected in the Congo; diagnostic resources are more limited there, particularly when you get to rural areas, treatment is more limited,” Schaffner said, adding there has not been a large rollout of the vaccine in that country. “One of the ways to protect the rest of the world is to come to grips in a more effective way with the source, we call that source control, and if we could control what's happening in the Congo and surrounding countries, then the risk of exporting this illness to numerous other countries around the world diminishes very substantially.”