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On May 18, and the confirmed a single case of monkeypox in a patient who had recently traveled to Canada. Cases have also been .

Monkeypox isn’t a new disease. The , when the virus was isolated from a child suspected of having smallpox in the Democratic Republic of Congo (DRC). Monkeypox is unlikely to cause another pandemic, but , fear of another major outbreak is understandable. Though rare and usually mild, monkeypox 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 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 monkeypox?

Monkeypox belongs to the Poxviridae family of viruses, which includes smallpox. This electron microscopic image shows a monkeypox virion, obtained from a clinical sample associated with the 2003 prairie dog outbreak. It is a thin section image from of a human skin sample. On the left are mature, oval-shaped virus particles, and on the right are the crescents and spherical particles of immature virions.

A cousin of smallpox

is caused by the monkeypox virus, which belongs to a subset of the Poxviridae family of viruses called Orthopoxvirus. This subset includes the smallpox, and cowpox viruses. While an , African rodents are suspected to play a part in transmission. The monkeypox virus has only been isolated twice from an animal in nature. is currently only available at Laboratory Response Network labs in the U.S. and globally.

The name “monkeypox” comes from the of the illness in animals in 1958, when two outbreaks occurred in monkeys kept for research. However, from monkeys to humans, nor are monkeys major carriers of the disease.

Epidemiology

Since the first reported human case, monkeypox has been found in , 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 .

The was in 2003, from an outbreak in Texas linked to a shipment of animals from Ghana. There were also travel-associated cases in in Maryland.

Because monkeypox is closely related to smallpox, the smallpox vaccine can against infection from both viruses. Since smallpox was officially eradicated, however, for the U.S. general population were stopped in 1972. Because of this, monkeypox has been in unvaccinated people.

Transmission

The virus can be through contact with an infected person or animal or contaminated surfaces. Typically, the virus enters the body through broken skin, inhalation or the mucous membranes in the eyes, nose or mouth. Researchers believe that human-to-human transmission is mostly through inhalation of large respiratory droplets rather than direct contact with bodily fluids or indirect contact through clothes. Human-to-human transmission rates for monkeypox have been .

are worried the virus may currently be spreading undetected through community transmission, possibly through a new mechanism or route. Where and how infections are occurring are still under investigation.

Signs and symptoms

Monkeypox lesions on a child in Liberia in 1971

After the virus enters the body, it starts to through the body via the bloodstream. Symptoms usually don’t appear until one to two weeks after infection.

Monkeypox produces smallpox-like skin lesions, but are usually milder than those of smallpox. Flu-like symptoms are common initially, ranging from fever and headache to shortness of breath. One to 10 days later, a rash can appear on the extremities, head or torso that eventually turns into blisters filled with pus. Overall, symptoms usually last for two to four weeks, while skin lesions usually scab over in 14 to 21 days.

While monkeypox is rare and usually non-fatal, of the disease kills . The form of the virus currently circulating is thought to be milder, with a fatality rate of less than 1%.

Vaccines and treatments

is primarily focused on relieving symptoms. According to the CDC, no treatments are available to cure monkeypox infection.

Evidence suggests that the smallpox vaccine can help prevent monkeypox infections and decrease the severity of the symptoms. One vaccine known as is licensed in the U.S. to prevent monkeypox and smallpox.

Vaccination after exposure to the virus may also help decrease chances of severe illness. The CDC currently recommends smallpox vaccination only in people who have been or are likely to be exposed to monkeypox. are at high risk.

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