The global eradication of smallpox more than 40 years ago was one of the greatest achievements in public health history, vanquishing a cause of death, blindness and disfigurement that had plagued humanity for at least 3,000 years. However, its success led to the end of a global vaccination program that provided protection against related diseases. Those include mpox, which has spilled over from its animal hosts to infect humans in West and Central Africa with increasing frequency since the 1970s. Now a mutated strain of the mpox-causing monkeypox virus has been detected in several African countries, leading the World Health Organization as well as continental health authorities to declare a health emergency.
What’s mpox?
Mpox is a less contagious cousin of smallpox with generally milder symptoms, although it still can be lethal. While about 30% of smallpox patients died, the fatality rate for mpox ranges from less than 0.1% to as high as 6%. The disease was discovered at the Statens Serum Institut in Copenhagen in 1958, where it was spreading in monkeys kept for research. That led to its former designation: monkeypox. Although the main animal source of the monkeypox virus hasn’t been identified, rodents are suspected of playing a part in transmission. The WHO changed the name of the disease to mpox in 2022 to curb what it called racist and stigmatising language surrounding the infection.
What are the symptoms of mpox?
In a multinational outbreak in 2022, mpox tended to follow a pattern starting with fever, muscle aches, fatigue, headache, swelling of the lymph nodes and other flu-like symptoms. Within a few days of fever onset, patients develop a rash that can develop into fluid-containing pustules or lesions that may appear on various parts of the body, including the genital and anal regions. These lesions can be painful and may lead to complications, especially if they occur in sensitive areas such as the mouth or rectum. If a lesion forms on the eye, it can cause blindness. The illness typically lasts two to four weeks, according to the WHO, and patients are infectious from the time symptoms start until the sores heal. Mortality is higher among children and young adults, and people with weak immune systems are especially at risk of severe disease. Infection during pregnancy poses severe risks to the mother along with the threat of congenital infection and pregnancy loss. Rare complications include inflammation of the heart muscle and brain, as well as seizures.
What’s different about the latest mpox outbreak?
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Children and adolescents have been most affected in the outbreak that’s now spreading in Africa, with youth under the age of 15 accounting for two-thirds of mpox cases and 82% of deaths. The current variant is also reported to be spreading faster through sexual contact, like the milder strain known as clade IIb that erupted globally in 2022. A report in June found 29% of confirmed cases of the new strain were among sex workers. However, mpox isn’t considered a sexually transmitted disease because it also spreads via other forms of close contact. The current variant is related to a more virulent strain called clade I; the rate of deaths among reported cases in the Democratic Republic of Congo is over 3%. Stemming the spread is also proving difficult in a region where other diseases such as Ebola, cholera, measles and malaria have devastated communities and left health systems fragile. In the DRC, renewed fighting has increased the number of displaced people living in crowded camps. Sexual violence makes it harder to respond to a disease that’s already freighted with shame and stigma. The DRC has some 17,500 cases in 2024 through mid-August, surpassing its infections in all of last year. More than 100 cases have been reported Burundi and three other African nations, although that’s likely an undercount. The first-known infections outside Africa related to the DRC outbreak were reported by Sweden and Thailand in mid-August.
What else is unusual?
There have been multiple chains of human-to-human transmission, with genetic changes in the circulating virus further complicating diagnosis. While Africa is the only continent where monkeypox virus is endemic, this variant has spread beyond previously known areas. Another concern is that some mpox patients may also have HIV, since Africa has the highest number of people living with the immune-system impairing virus.
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How does it spread?
Monkeypox virus doesn’t usually spread easily between people. Close skin-to-skin contact with the virus from an infected person or animal — such as touching a lesion or contaminated object — is the main pathway. The pathogen enters the body through broken skin, the respiratory tract or the mucous membranes in the eyes, nose, mouth, vagina, rectum and anus. Tests on various patient specimens, including saliva, rectal swabs and semen, have found traces of the virus. A 2022 study from the UK found that more than half of infections were spread by infected individuals who hadn’t yet developed mpox symptoms. Emerging evidence suggests that people incubating the disease may transit monkeypox virus for up to four days prior to symptom onset. There are no confirmed instances of airborne transmission and common household disinfectants can kill it.
How is it treated?
The illness is usually mild and most people recover within a few weeks; treatment is mainly aimed at relieving symptoms. The CDC says smallpox vaccine, antivirals and vaccinia immune globulin can be used to treat mpox as well as control it. Early results from a patient study indicate that the antiviral drug tecovirimat isn’t effective against the clade I monkeypox strains.
What about prevention? Is there an mpox vaccine?
Public health experts say limiting the spread will require global surveillance, coordination and concerted community support, all of which will need financing. Perhaps most importantly, Africa needs adequate supplies of vaccines, the first of which are expected to arrive in early September. Governments including the US, Japan, and Germany have pledged donations totaling more than 4 million doses. Bavarian Nordic A/S, maker of the Imvanex vaccine also known as Jynneos, and Emergent BioSolutions Inc., which makes an older inoculation called ACAM2000, have also announced donation plans. These vaccines, along with KM Biologics’ LC16, were developed for smallpox. During the 2022 outbreak, two injections of the Jynneos shot were found to be up to 85% effective at preventing mpox in adults. LC16 and ACAM2000 are administered as single doses using a bifurcated needle — a 60-year-old device that pricks the skin multiple times to help stimulate an immune response.
What’s being done at the international level?
The WHO announced in late August a preparedness and response plan, and sought US$135 million ($176.4 million) to cover the first six months of the plan starting in September. The funds will be used to improve surveillance and diagnostics, helping scientists get a better grasp of how the virus has changed and what exactly is driving the spread. Money raised will also help countries plan response strategies, minimize animal-to-human transmission, and procure vaccines.
