In May 2022, an outbreak of monkeypox began in Europe and North America. While so far this outbreak has mainly affected gay and bisexual men, anyone can get monkeypox through close personal contact.

 

What is monkeypox?

Monkeypox is caused by a virus related to smallpox; both are members of the orthopox family. It typically produces flu-like symptoms, swollen lymph nodes and a rash.

Monkeypox is not a new disease. It was first discovered in laboratory monkeys in 1958, and the first human case was identified in 1970 in the Democratic Republic of Congo. Before the current outbreak, it was mostly seen in Central and West Africa, though cases have periodically been detected elsewhere, mostly among travelers. Two isolated cases were reported in the United States in 2021, and in 2003, an outbreak that involved nearly 50 people in the Midwest was linked to pet prairie dogs.

How is monkeypox transmitted?

The monkeypox virus is transmitted from animals, primarily rodents, and from person to person through close contact. This can include skin-to-skin contact, kissing and contact with contaminated clothing, bed linens, towels or surfaces. It also can be transmitted through respiratory droplets at close range, but it does not spread over longer distances like the coronavirus that causes COVID-19. It is not known whether monkeypox is directly sexually transmitted in semen, vaginal fluid or feces, but it can spread via contact with sores during sex (like herpes and syphilis). Mother-to-child transmission can occur during pregnancy or close contact during or after birth. Experts think transmission happens mainly—or perhaps only—when people are symptomatic.

Who is at risk for monkeypox?

Before the latest outbreak in non-endemic countries, monkeypox was often acquired through contact with infected animals (for example, via bites or handling wild game), and it was not thought to spread easily from person to person. Most affected people in the current outbreak are gay, bisexual and other men who have sex with men. Many cases have been liked to large events, including a Pride festival in the Canary Islands, and saunas.

However, anyone—including women and children—can get monkeypox through close personal contact. Household members and health care workers caring for people with monkeypox should take precautions.

What are the symptoms of monkeypox?

Monkeypox has an incubation period of up to three weeks before symptoms start, and the illness usually lasts two to four weeks. It typically causes flu-like symptoms, such as fever, fatigue, headache and muscle aches, as well as swollen lymph nodes. Its characteristic feature is a rash that can appear on the face, in the mouth or elsewhere on the body. The sores, which may be painful or itchy, typically start out as flat red spots and progress to firm, raised lesions that fill with clear fluid and then pus.

Monkeypox lesionsCourtesy of the University of Malaga

The sores may resemble common sexually transmitted infections (STIs) or chickenpox. Like syphilis lesions, they often appear on the palms of the hands and soles of the feet. In the current outbreak, many men have presented with lesions on the genitals or in the anal area. Some have only a small number of lesions and have not reported accompanying flu-like symptoms. Some have tested positive for other STIs in addition to monkeypox.

How severe is monkeypox?

Most people with monkeypox recover without treatment. But the sores can leave scars, and people with more severe disease may develop complications, including bacterial infection of the lesions, sepsis (blood infection), pneumonia, encephalitis and vision loss due to lesions in the eyes. Severe outcomes are more common among children, pregnant people and immunocompromised people. People on antiretroviral therapy with well-controlled HIV do not appear to be at greater risk, but those with unsuppressed HIV and a low CD4 count may have worse outcomes.

There are two main monkeypox strains in Africa, one of which has a fatality rate of around 10% and the other around 1%. The milder form is circulating in Europe and North America. There have been no deaths so far in the current outbreak.

How is monkeypox treated?

People with mild to moderate monkeypox usually do not need treatment beyond supportive care, such as bed rest, over-the-counter medications for flu-like symptoms and keeping lesions clean. Some people may need stronger pain management. For more severe cases, antiviral medications used to treat smallpox can also be used for monkeypox, including tecovirimat (TPOXX), cidofovir (Vistide) and brincidofovir (Tembexa). Vaccinia immune globulin (smallpox antibodies) is another option.

Is there a vaccine for monkeypox?

Smallpox vaccination can prevent monkeypox as well. In fact, cases have risen in recent decades since routine vaccination was discontinued after smallpox was eradicated in 1980. In the United States, routine smallpox vaccination was halted in 1972, meaning most people around age 50 or older have been vaccinated. Protection appears to be long-lasting, though immunity may wane over time.

An older live vaccinia virus vaccine (ACAM2000) can cause side effects, especially in people with compromised immunity or skin conditions. In 2019, the Food and Drug Administration approved a new, safer non-replicating smallpox and monkeypox vaccine (Jynneos, also known as Imvanex and Imvamune). The United Stated maintains a national stockpile of smallpox vaccines, but these are mostly the older version, and Jynneos is in short supply.

Monkeypox can be contained through ring vaccination or targeted vaccination of close contacts of an infected person. The Jynneos vaccine is now being given to high-risk contacts of known cases and health care workers. Because monkeypox has a long incubation period, vaccines can be administered before or to two weeks after exposure, but it works best if given within four days. Experts do not recommend vaccination for the general population, but some are considering vaccinating groups at higher risk, especially gay and bi men with multiple sex partners.

How is monkeypox prevented?

People with monkeypox should isolate for three weeks. Close contacts, including sex partners, family members and housemates, are at greatest risk. Monkeypox is infectious until the sores heal completely and scabs fall off.

Cover sores with clothing or bandages to lower the risk of transmission. Because the virus may be transmitted through respiratory droplets during face-to-face contact, cover coughs and sneezes; wearing a well-fitted mask can help prevent transmission to close contacts. Avoid sharing sex toys or personal items like toothbrushes; wash your hands often; promptly wash clothes, towels and bed linens in hot water; and disinfect surfaces that come into contact with sores. It is not known whether condoms can prevent transmission via semen. Health care workers caring for monkeypox patients should use standard infection control precautions.

At this time, most experts do not recommend canceling events or closing venues where people have close contact, including sex. However, people with a rash or other symptoms should refrain from sex and other close contact, seek medical care, get tested and cooperate with contact tracing. Those who think they may have been exposed should self-monitor for symptoms for three weeks.

See these resources for more information:
CDC: Monkeypox
CDC: Social Gatherings, Safer Sex and Monkeypox
World Health Organization: Monkeypox
UK Health Security Agency: Monkeypox

Last Reviewed: June 13, 2022