On Aug. 14, 2024, the World Health Organization declared mpox a public health emergency of international concern. There have been over 15,600 cases and over 530 deaths reported in the Democratic Republic of the Congo and neighboring countries in Africa. The disease had previously caused a global outbreak from 2022 to 2023.
Mpox – previously called monkeypox – isn’t a new disease. The first confirmed human case was in 1970, when the virus was isolated from a child suspected of having smallpox in the Democratic Republic of Congo (DRC). Though usually mild, mpox can still potentially cause severe illness. Health officials are concerned that more cases will arise with increased travel.
I’m a researcher who has worked in public health and medical laboratories for over three decades, especially in the realm of diseases with animal origins. What exactly is happening in the current outbreak, and what does history tell us about mpox?
A cousin of smallpox
Mpox is caused by the monkeypox virus, which belongs to a subset of the Poxviridae family of viruses called Orthopoxvirus. This subset includes the smallpox, vaccinia and cowpox viruses. While an animal reservoir for monkeypox virus is unknown, African rodents are suspected to play a part in transmission. The monkeypox virus has only been isolated twice from an animal in nature. Diagnostic testing for mpox is currently only available at Laboratory Response Network labs in the U.S. and globally.
The name “monkeypox” comes from the first documented cases of the illness in animals in 1958, when two outbreaks occurred in monkeys kept for research. However, the virus did not jump from monkeys to humans, nor are monkeys major carriers of the disease.
The virus that causes mpox belongs to the Poxviridae family of viruses, which includes smallpox.
CDC/ Cynthia S. Goldsmith
Epidemiology
Since the first reported human case, mpox has been found in several other central and western African countries, with the majority of infections in the DRC. Cases outside of Africa have been linked to international travel or imported animals, including in the U.S. and elsewhere.
The first reported cases of mpox in the U.S. was in 2003, from an outbreak in Texas linked to a shipment of animals from Ghana. There were also travel-associated cases in July and November 2021 in Maryland. The outbreak of mpox that began May 2022 is ongoing.
Because mpox is closely related to smallpox, the smallpox vaccine can provide protection against infection from both viruses. Since smallpox was officially eradicated, however, routine smallpox vaccinations for the U.S. general population were stopped in 1972. Because of this, mpox has been appearing increasingly in unvaccinated people.
