Note:
- The virus that causes monkeypox is similar to the one that causes smallpox. But monkeypox has much lower death and transmission rates.
- The most common way for someone to get monkeypox is from direct contact with an infected animal. Human-to-human spread is possible through large respiratory droplets or direct skin-to-skin contact.
- Most people with monkeypox make a full recovery. Death rates vary between outbreaks and have ranged from 0% to 10%. No one died in the last outbreak in the U.S.
Monkeypox is a viral infection. It’s similar to the virus that causes smallpox, and it leads to a similar rash. Fortunately, monkeypox is much less deadly than smallpox. And it does not spread from person to person as easily.
Monkeypox can infect both humans and animals, which is how it got its name. Researchers identified the first case in monkeys in the 1950s. Then they confirmed the first case of monkeypox in humans in the 1970s in Africa. Most of the time, monkeypox in humans happens from exposure to sick animals. Human-to-human spread is less common.
Most cases of monkeypox in humans have been in Africa. But there have been small clusters and outbreaks in countries where the virus is much less common, including the U.S.
What to know about recent monkeypox outbreaks
The biggest monkeypox outbreak outside of Africa happened in the U.S. in 2003, when 70 people came down with the illness. The outbreak started when people imported prairie dogs that were temporarily housed with infected rodents from Ghana. The virus did not spread far beyond the people who had direct contact with the animals, and nobody died from the infection.
In July 2021, one person in the U.S. developed monkeypox after returning from Africa. The same thing happened again in November 2021 (a person had recently traveled back to the U.S. from Africa). In both cases, no one else was infected.
In May 2022, authorities identified several small clusters of people with monkeypox across North America and Europe. They found the first case in the U.S. in someone who recently traveled from Canada. The CDC continues to monitor the country for potential new cases. The source of these clusters is not yet clear. But it may be related to very close, direct physical contact with someone who is infected. We discuss spread and transmission in more detail below.
How many monkeypox cases occur each year?
Most cases of monkeypox occur in Central and West Africa. In these regions, the virus is endemic, which means it exists naturally. The Democratic Republic of the Congo has had the most cases of monkeypox, where there are more than 1,000 cases each year. Nigeria has also had an increasing number of cases — over 400 infections have happened since 2017. There have been small outbreaks in other African countries.
Outbreaks rarely occur in countries outside of Africa, and they’re usually related to travelers. These outbreaks include:
- U.S.: 2003
- U.K: 2018 and 2021
- Israel: 2018
- Singapore: 2019
How is monkeypox transmitted?
Monkeypox is most commonly transmitted to humans from infected animals — either by direct contact with body fluids or through a bite. Scientists first discovered monkeypox in monkeys, but the virus also infects rodents and squirrels that live in Africa. We don’t know which animals are responsible for most cases of human infections.
Human-to-human transmission is less common, but it can happen. And it usually requires close contact with someone who is sick. The two main ways that monkeypox spreads between humans are through:
- Large respiratory droplets: Monkeypox spreads through bigger respiratory droplets than other viruses. This means it can only travel a few feet from the person who is infected. So experts believe someone needs to be very physically close to someone who is sick — and for a long period of time — to catch the virus this way.
- Contact with body fluids or infected skin lesions: The virus can be in bodily fluids and the fluid inside the skin pustules that form during infection. People can come into contact with infected material during direct physical contact with someone who is sick. Experts believe this can happen during sexual intercourse. It’s also possible someone can acquire infection from indirect contact, like through shared bed sheets.
Symptoms often show up 7 to 14 days after someone is exposed and infected. But it can be as short as 5 days — or as long as 21 days. This timeframe is also known as the “incubation period.”
Signs and symptoms of monkeypox
The most recognizable sign of monkeypox is a rash. It can begin and then spread to many areas on the body. It most commonly occurs on the face, arms, and legs (including on the palms and soles of the feet). But the rash can also appear on the trunk, genital area, as well as the eyes and mouth.
The rash changes in appearance as the infection progresses and then resolves. It can start off looking like red bumps. It turns into small blisters and then fluid-filled pustules that eventually scab over.
But there are some symptoms that usually start a few days before the rash, such as:
- Headaches
- Muscle aches
- Fever
- Chills
- Swollen lymph nodes
- Fatigue
The symptoms of monkeypox usually last 2 to 4 weeks.
How do you treat monkeypox?
Most people fully recover from a monkeypox infection without any specific treatment. But some people may need supportive care to help them. These include things like:
- Acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) to help with fever
- Intravenous (IV) fluids to help people at risk of dehydration, like very young children or older adults
A few of the medications for smallpox might be helpful for monkeypox, too. This is because these infections are similar and belong to the same family of viruses. But scientists have only tested them against monkeypox in animals, so we don’t know if they’re safe or effective in humans.
Monkeypox vaccine
There’s a vaccine that can protect people against monkeypox. The smallpox vaccine also offers some protection against monkeypox. But experts only recommend these vaccines for certain groups of people who are at high risk for coming into contact with monkeypox or smallpox. Examples include military personnel or laboratory employees who handle the viruses for research.
Researchers are still trying to figure out if these vaccines can prevent infection or more serious illness after someone has already been exposed.
How deadly is monkeypox?
The monkeypox death rate varies between countries and outbreaks. In some outbreaks, it has killed 1 out of every 10 people with the infection. In other outbreaks, it has not been deadly at all. For example, nobody died during the 2003 U.S. outbreak. The death rate may be higher in people who have weak immune systems — like very young infants or older adults. It may also be more serious when the level of initial exposure is higher — like when someone gets bitten by an infected animal, rather than just coming into contact with the rash. But overall, very few people die from monkeypox.
Monkeypox can sound like a scary infection, especially given its relation to smallpox. But it’s much less deadly than smallpox, and it does not spread as easily between humans. In fact, most human cases occur when someone comes in contact with an infected animal.
Most cases of monkeypox occur in African countries and do not lead to large outbreaks. Vaccines are available for people who have a high risk of coming into contact with the virus. Luckily, monkeypox is not a threat for most people in the U.S.
References
Centers for Disease Control and Prevention. (2021). About monkeypox.
Centers for Disease Control and Prevention. (2021). Signs and symptoms.
Centers for Disease Control and Prevention. (2021). Transmission.
Centers for Disease Control and Prevention. (2021). Treatment.
Centers for Disease Control and Prevention. (2022). 2022 United States monkeypox case.
Durski, K. N., et al. (2018). Emergence of monkeypox — West and Central Africa, 1970–2017. Morbidity and Mortality Weekly Report.
Maskalyk, J. (2003). Monkeypox outbreak among pet owners. Canadian Medical Association Journal.
World Health Organization. (2022). Monkeypox.
Written by: Katie E. Golden, MD | Reviewed by Karla Robinson, MD