What is Mpox, How Does It Spread and Is There a Vaccine? All You Need to Know
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 dangerous, mutated strain of the virus has been detected in at least six 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 has been about 3% to 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 mpox disease hasn’t been identified, rodents are suspected of playing a part in transmission. The World Health Organization changed the name of the disease to mpox in 2022 to curb what it called racist and stigmatizing language surrounding the infection.
What does mpox do?
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 now?
Children and adolescents have been most affected in the outbreak that’s now spreading in Africa, with more than 60% of known fatal cases under the age of 5. 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 almost 5%. Stemming the spread is also proving difficult in a region where other diseases such as Ebola, cholera 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 15,000 cases in 2024 through Aug. 4, surpassing its infections in all of last year. At least 50 confirmed cases have been reported recently in other regional countries, although that’s likely an undercount.
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 mpox 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.
How does it spread?
Mpox doesn’t usually spread easily between people. Close 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, rectum and anus. Tests on various patient specimens, including saliva, rectal swabs and semen, have found traces of the virus. 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.
What about prevention?
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. Bavarian Nordic A/S, maker of the Imvanex vaccine also known as Jynneos, said it has pledged to donate doses for African countries. Immunization typically entails two injections administered four weeks apart.
What’s being done at the international level?
The Africa Centres for Disease Control and Prevention invoked a public health emergency of continental security, the first time the agency has used the power since gaining it in 2023. WHO Director-General Tedros Adhanom Ghebreyesus on Aug. 14 designated the outbreak in central Africa a public health emergency of international concern, paving the way for global cooperation to stop the spread of the virus. The last time the WHO declared such an emergency was for the 2022 mpox outbreak.
