Fact Check- Monkeypox is not the same disease as Leprosy

A widely shared social media post likening the current monkeypox outbreak to biblical-era leprosy outbreaks has some users confused, others amused. The post says but does not provide any evidence that monkeypox, a viral disease, and leprosy, a bacterial infection, are actually the same illness. They are not.

The Facebook post (here) shared more than 12,000 times, states, “THIS IS SIMILAR TO THE DAYS OF NOAH" and describes ancient interactions with animals or snakes that led to disease transmission or venomous bites, contrasting that period with the present. Today, people vaccinate and treat animals for diseases they might carry, the post continues, “because we know how dangerous and what bacteria and virus they animals have."

Highlighting the analogy between past and present, the post adds, “This is what monkeypoxs really is. It’s leprosy and it’s in the bible… ”

Responses to the post include strings of laughing emoji, and “So two completely different diseases are the same? Mmmmkay” as well as “Amen!” and “Plagues coming in the last days.” Another user writes, “Leprosy is caused by a bacterium called Mycobacterium leprae, not the monkeypox virus. Reported for false information (to no one’s surprise.)”

Leprosy, also known as Hansen’s disease, is indeed caused by Mycobacterium leprae, a bacterium in the same family as the tuberculosis bacterium. Leprosy is the oldest disease known to be associated with humans, with evidence of it dating back more than 4,000 years, according to science website The Conversation (here).

The leprosy-causing bacteria can incubate for three to five years before symptoms appear, and the main manifestations of the disease are nerve damage that can be permanent and crippling, as well as disfiguring lesions of skin tissue. The disease is hard to transmit from person to person, according to the Microbiology Society, although it can be transmitted by respiratory droplets, such as those in a cough (here).

The leprosy-causing bacteria are also widespread among armadillos, and modern cases in the Americas are often linked to exposure to those animals (here).

Monkeypox is caused by a virus in the same family as the smallpox virus, and was first identified in a 9-month-old baby in the Democratic Republic of Congo in 1970, according to the World Health Organization (here). Prior to the current outbreak, the disease was typically associated with having direct contact with an animal carrying it, such as the African green monkey, and onward transmission from person to person was considered unusual (here).

The disease is primarily transmitted between people by direct contact with the skin lesions that monkeypox causes, and the fluid they contain, including by handling items such as bedsheets contaminated by those fluids. It can also be transmitted by droplets of “respiratory secretions” like saliva and mucus, such as in a cough, according to the U.S. Centers for Disease Control and Prevention (here).

Symptoms typically appear within three weeks of exposure, and include painful skin lesions, fever and other flu-like symptoms that usually resolve within two-to-four weeks.


Misleading. An analogy focused on the fact that bacterial leprosy and viral monkeypox can both be transmitted from animals to humans could be misunderstood to suggest they are the same illness, which they are not.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts  here .