Monkeypox has almost nothing to do with monkeys. Here's why the disease was given its misleading name.

• Cases of monkeypox spreading outside of its normal area in Africa are causing concern.
• The disease was first spotted in monkeys in 1958, which gave it its name.

More than a hundred confirmed cases of monkeypox in humans have been identified outside of African countries since early May.

Monkeypox cases outside of Africa are rare, so this outbreak has raised alarm bells around the world.

In spite of its name, monkeypox in humans doesn't have much to do with monkeys. Here's how the disease got its misleading name.

Why is it called monkeypox?

Humans aren't the only primates that can catch monkeypox. Monkeys can catch it, too, and that's where the disease got its name.

The virus that causes monkeypox was first spotted in 1958 among a colony of monkeys used for research that was imported to Denmark. The disease caused lesions that were similar to those seen in smallpox — a cousin of monkeypox — so the scientists called it monkeypox.

More than a decade later, in 1970, the first human case of monkeypox was identified. It was diagnosed in a child in the Democratic Republic of Congo.

"The name of this virus is a terrible misnomer. But we're not changing it today," Andrea McCollum told Insider.

McCollum is an epidemiologist with the US Centers for Disease Control and Prevention who has been investigating monkeypox outbreaks for years in several African countries.

Are monkeys involved in human monkeypox?

The short answer is no: Monkeys likely have nothing to do with the disease humans are getting.

Monkeypox is a zoonotic disease, which means that humans catch the virus from animals that are sick.

Humans are thought to be exposed to the virus occasionally only by close contact with the ill animals — for instance, through scratches, bites, or the preparation of bush meat. Human-to-human transmission can happen, but is thought to be rare.

We don't know exactly which species carry monkeypox in the wild. Scientists believe they are contained within West and Central Africa.

But primates aren't likely to be the primary source of human infections. One or several species of small rodents found in West and Central Africa are probably to blame, the World Health Organization said.

"People who are living in forested areas that come into contact with those small animals occasionally get infected," said Jimmy Whitworth, an infectious-disease expert and professor at the London School of Hygiene and Tropical Medicine. "That's the normal way in which we see human cases."

This hypothesis is supported by an outbreak of monkeypox in the US in 2003. The cases were linked back to prairie dogs that had been exposed to a Gambian pouched rat imported from West Africa.

This latest monkeypox outbreak, happening away from identifiable vector animals in West Africa, is concerning officials. Humans in Europe and North America — some with no recent travel history in the countries where monkeypox is endemic — now appear to be transmitting the disease to each other. Transmission seems to be happening via close skin-to-skin contact with infected lesions on their bodies.