As experts learn more about mpox outbreaks, news and information changes. For the latest on mpox, please visit the Centers for Disease Control and Prevention

Monkeypox, renamed mpox to reduce stigma, is a rare infectious disease caused by a virus in the Orthopoxvirus genus, which also causes smallpox. Mpox, however, is less contagious and causes a milder illness than smallpox.

Mpox disease is typically geographically focused in tropical rainforest areas in central Africa and western African countries. As of November 30, 2022, almost 30,000 cases of mpox have been reported in the United States. While the recent outbreak of this rare disease raises concern, mpox is most often a self-limited illness with a low fatality rate.

What is monkeypox (mpox)?

Mpox is a viral zoonosis, which means it is a virus passed from infected animals to humans. While the virus is similar to what causes smallpox, it is transmitted very differently from the virus that causes COVID-19. Mpox has been reported in humans in several central and western African countries where it is considered endemic, or constantly present in that area. Mpox has also been reported in people throughout the world as sporadic clusters, usually related to international travel to endemic areas or imported infected animals.

The first cases of mpox were identified and named in 1958 when outbreaks of an unknown illness causing lesions was reported in groups of monkeys used for research. Mpox was first described as causing infection in a human in 1970 in the Democratic Republic of the Congo, where—in addition to west Africa—most present-day infections continue to be reported.

Over time, outbreaks have occurred in Africa and in other countries. In 2003, the first mpox outbreak happened in the United States. It was linked to contact with prairie dogs sold as household pets, which had been infected from co-habitant Gambian giant rats imported from Ghana. This outbreak resulted in approximately 50 reported human cases. Since then, sporadic cases have been reported in travelers from Nigeria to other countries, including the United States in July and November 2021.

Since early May 2022, cases and clusters of mpox have been reported across many geographical areas—in endemic and non-endemic countries—for the first time. Current Infection rates are much smaller in number (in the thousands) than the COVID-19 pandemic, which has affected people in the millions. However, the sharp rise in numbers since the first report in May 2022 has resulted in the World Health Organization (WHO) declaring mpox a Public Health Emergency of International Concern (PHEIC) on July 23, 2022.

Currently, data indicates that most cases of mpox in the U.S. are among gay men, bisexual men, or men who have sexual intercourse with other men, and it disproportionately affects minority groups. Even so, anyone who has been in close physical contact with someone who has mpox is at risk of contracting the illness, regardless of sexual orientation or gender.

Transmission

Mpox is contagious and while most cases have historically been zoonotic, aka occurring after close or direct contact with infected animals such as rodents and primates, human-to-human transmission can occur and is the primary driver behind the current outbreak, mostly through intimate contact with someone who has mpox.

Transmission occurs through contact with bodily fluids, such as fluid-filled skin lesions, saliva, or respiratory droplets, prolonged face-to-face contact, hugging, kissing or massage, or through anal, oral, or vaginal intercourse or intimate contact with genitalia. You can also catch mpox through contact with materials, like clothes or bed sheets, contaminated with the virus. It is not known whether mpox can be spread by vaginal fluids, semen, urine or feces.

People with mpox may transmit it to animals through close contact like petting, hugging, licking, sharing sleep areas, and sharing food. Animals may pass mpox to people as well–mainly via exposure to infectious fluids or scabs. A pregnant person can also spread the virus to their fetus.

Incubation period

Following transmission, the virus spreads to local lymph nodes and can then go on to infect other organs. This incubation period lasts about one to two weeks, after which symptoms develop.

Symptoms

Symptoms of mpox include fever, rash, tiredness, chills, itching, headache, muscle aches, swollen lymph nodes, rectal pain, rectal bleeding, rectal cramping, pus or blood in the stool, nausea or vomiting, abdominal pain, conjunctivitis, and lesions.

Mpox lesions are similar to chickenpox. Lesions usually start in the mouth and throat before appearing on the skin and other parts of the body. The rash evolves from macules (lesions with a flat base) to papules (slightly raised, firm lesions) then vesicles (lesions filled with clear fluid) to pustules (lesions filled with yellow fluid). After this phase, pustules will begin to dry up, scab, and fall off. Once the lesions scab over, the infected person is no longer considered infectious.

Symptoms of mpox generally last two to four weeks, but severe cases can occur with long-lasting effects.

How serious is mpox?

The recent outbreak of mpox cases is mostly in countries that have not historically reported mpox. Catching mpox remains a low public health concern overall. The CDC has issued travel recommendations which include avoiding travel if displaying mpox symptoms, and what to do if you develop mpox. There remains much to be learned from the current outbreak, but guidance has been developed on steps to take to prevent contracting mpox.

Is mpox fatal?

The historical mpox death rate has been reported as exceeding 10%, with more recent data showing mortalities less than 5%. Children and those with weakened immune systems may be most susceptible to the disease and its complications. The current outbreak has caused 19 fatalities in the United States, to date.

What to do if you think you have mpox

Always contact your healthcare provider with any concerns or symptoms. If you believe you have been exposed to and or are sick with mpox, you should limit your exposure to other people until assessed and cleared by healthcare professionals or public health officials. Possible human cases will be reported to state health departments, who will go on to contact the CDC.

Be cognizant if you develop a rash and have traveled to central or west African countries (or other parts of the world where confirmed cases have been reported) during the month before your symptoms appear—or if you have been in contact with someone with confirmed or suspected mpox.

The rash associated with mpox can be mistaken with other more well-known diseases, so a lab-based test is important for a definitive diagnosis. The gold-standard test is detection of viral DNA by polymerase chain reaction (PCR), with samples obtained from the skin, fluid, or scabs collected from skin lesions or biopsy.

Mpox treatment

Mpox is often a self-limited infection requiring only supportive care to manage symptoms and treatment of any possible secondary bacterial infections that may occur.

An antiviral medication known as tecovirimat (TPOXX) received FDA approval in 2018 to treat smallpox, but there is currently very limited data on its efficacy in humans to treat mpox. A recently published case series on individuals infected with mpox, including one patient treated with tecovirimat, has suggested it may shorten the duration of illness and viral shedding. Two trials of tecovirimat among patients with mpox are currently being conducted.

The CDC holds a non-research expanded access Investigational New Drug (EA-IND) protocol which allows for tecovirimat use during this outbreak, and may be recommended for people at higher risk of getting severely ill or with severe disease.

The antiviral Tembexa (brincidofovir) was approved by the FDA in 2021 to treat smallpox in adults, children, and neonates and may be approved for emergency authorization on an individual basis, but only if severe illness, risk of serious illness progression, or unsuccessful treatment and worsening illness with tecovirimat occurs.

Another antiviral, cidofovir, which is available via injection, may be considered, but it’s efficacy against mpox is unknown.

Vaccinia immune globulin (VIG) is a final potential treatment option, but data is lacking and would be purely investigational.

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Mpox prevention

Preventing mpox infection is best accomplished by avoidance of contact with those known to be infected and any contaminated materials, practicing good hand hygiene, and limiting contact with both dead or live wild animals—including eating or preparing wild game, or using products derived from wild animals from Africa.

Vaccination against smallpox has proven to be approximately 85% effective in preventing mpox, so those with prior smallpox vaccination that become infected may present with a milder form of illness and perhaps contribute to the lower fatality rate observed present-day. Due to the eradication of smallpox based on broad vaccination campaigns, these first-generation vaccines are no longer available, and smallpox vaccination is not widely provided.

There are currently two licensed vaccines for smallpox, Jynneos and ACAM2000, both of which are part of the U.S. Strategic National Stockpile (SNS). Jynneos is also licensed for mpox, and was FDA approved in 2019. This vaccine is administered as two subcutaneous injections, separated by four weeks. Jynneos may also be considered for post-exposure prophylaxis to minimize the potential development and/or severity of disease, and the first dose is recommended to be administered within 4 days from exposure to prevent disease; if administered between 4 to 14 days from exposure, vaccination may decrease disease severity but will unlikely prevent it.

On June 28, 2022, the Biden-Harris Administration announced a plan to roll-out a national mpox vaccine strategy to provide Jynneos for individuals at higher risk of exposure. ACAM2000 can also be requested by states and territories to supplement the available Jynneos supply. The CDC is currently recommending vaccination for people exposed to mpox or people more likely to get mpox, which includes those with known sexual partners in the past 2 weeks diagnosed with mpox or those with multiple sexual partners in the past 2 weeks in an area with known mpox.