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What causes Mpox? Diagnosis, prevention, and treatment

Medically reviewed by Leslie Greenberg, MD
Board-Certified Family Physician
Updated Jun 10, 2024  •  Published Aug 16, 2023
Fact Checked

Overview: What is mpox?

Mpox is a rare but highly contagious viral infection similar to smallpox. Known initially as monkeypox, the World Health Organization changed the name to mpox during the worldwide outbreak in 2022. Normally, the mpox virus infects rodents and other animals in the Congo and West Africa, but it can pass the viral infection to humans, who can then transmit the infection to other people. Before 2022, mpox infections were very rare in the U.S. and only associated with foreign travel or contact with infected animals. This changed in 2022 when mpox infections spread rapidly throughout the U.S., Europe, and South America. As of July 2023, over 30,000 cases of mpox have been reported in the U.S. and almost 90,000 worldwide. Almost all of these mpox cases were due to direct contact with infected people. 

Unlike mpox infections in Africa, healthcare professionals believe the virus has mainly spread through sexual contact in the current mpox outbreak. People who are vaccinated against smallpox are mostly immune to mpox. However, the smallpox vaccine was discontinued in the 1980s, so the majority of younger adults are not immune. Like smallpox infections, mpox generally runs its course for about four weeks and then resolves, but, unlike smallpox, the fatality rate of the current outbreak is very low, about 1%. 

RELATED: Is monkeypox deadly?

Key takeaways:

  • Mpox is a rare infection that (outside of Africa) mostly affects men who have not been vaccinated against smallpox, particularly men who have sex with other men. However, the virus can infect anyone regardless of age, sex, race, or ethnicity.

  • Mpox is caused by the mpox virus, an orthopox virus very similar to variola, the smallpox virus.

  • Outside of Africa, risk factors for Mpox include being unvaccinated for smallpox, male sex, and having close contact with an infected person.

  • Symptoms of Mpox include fever, chills, headache, feeling sick, muscle aches, backache, fatigue, and swollen lymph nodes followed by a blistering and pustule-forming mpox rash that begins near the site of infection and spreads to other parts of the body. The lesions eventually turn to scabs or crusts and slough off. Loss of appetite, nausea, vomiting, and diarrhea are the most common digestive system complaints during an infection. In the current mpox outbreak, many people have unique symptoms such as rectal bleeding, rectal pain, swelling, and stool blood.

  • Mpox usually requires a medical diagnosis.

  • Mpox generally requires isolation and supportive treatment, but people at a higher risk of severe infection or complications may be treated with antiviral medications or the smallpox vaccine. Mpox typically resolves without treatment within four weeks of the initial infection. 

  • Treatment of Mpox may include isolation, supportive treatment, antiviral medications, smallpox vaccine, or immunoglobulin treatment. 

  • Mpox is preventable through vaccination and avoiding infected people.

  • Use coupons for Mpox treatments, like Tpoxx (tecovirimat), to save up to 80%.

What causes mpox?

Mpox is caused by the mpox virus, a virus very similar to the smallpox virus. Unlike smallpox, mpox is an animal virus on the African continent that mainly populates rats, squirrels, monkeys, pigs, hedgehogs, and other animals. The virus can spread from animals to humans. Animal-to-human transmission was the primary cause of mpox cases before the 2022 outbreak of mpox. Infections were largely limited to countries in West Africa. Outside of Africa, mpox cases involved people who traveled to Africa or animals exported from Africa. 

People living in Africa primarily catch the virus from contact with animals primarily by hunting or eating them. The mpox virus can also be caught from animals through bites, scratches, contaminated surfaces, and physical contact with an animal.

People can spread mpox to other people in three ways:

  • Respiratory droplets

During the early stage of the infection, respiratory droplets are full of the mpox virus. Mpox is not easy to catch like a cold or flu, but close contact, like kissing, oral sex, or constant face-to-face contact, can spread the infection.

  • Contact with lesions

The blisters and pustules that form on the skin are full of the mpox virus, so skin-to-skin contact is a common way to spread the disease. In the 2022 outbreak, sexual transmission through oral or anal sex is the primary transmission of the virus.

  • Contaminated surfaces

Both recently contaminated bed linens and clothes have been shown to spread the virus from person to person. 

RELATED: What exactly is a pandemic?

Risk factors for mpox

For people who do not live or travel to West African countries, the major risk factors for contracting a mpox infection are:

  • Being unvaccinated for smallpox 

  • Male sex

  • Men who have sexual contact with other men

  • Close or constant exposure to people with a mpox infection

Is mpox serious? When to see a doctor

Mpox is a contagious virus that can cause serious complications. At the very least, an infection must avoid spreading the virus, so see a doctor or other healthcare professional to be evaluated and receive advice.

How is mpox diagnosed?

Diagnosis of mpox requires testing. Mpox is easily mistaken for other skin infections such as chickenpox, syphilis, scabies, measles, herpes, and bacterial skin infections. Before running tests, the clinician will start with a history and physical but will be most interested in the symptoms. The three key symptoms are fever, swollen lymph nodes, and pustular or blistering skin lesions.

To confirm the diagnosis, the clinician will test for the virus using a polymerase chain reaction (PCR) test. This will require two separate samples from the mpox lesions or dry scabs. If neither is possible, the clinician may take samples using other body fluids or by swabbing the inside of the mouth or nose. Some clinicians may choose to culture the virus or examine a sample under an electron microscope. Antibody tests are not administered.

Is mpox contagious?

Mpox is very contagious. In the recent outbreak, most infections spread through sexual contact, but the virus can be transmitted from person to person in many ways, including:

  • Skin-to-skin physical contact, such as casual touching, cuddling, or sexual contact

  • Mouth-to-mouth contact, such as kissing

  • Mouth-to-skin contact, such as kissing skin or oral sex

  • Respiratory droplets through face-to-face contact, talking, breathing, or prolonged close contact

  • Contaminated surfaces such as bed linens, blankets, or clothing

People diagnosed with mpox should isolate themselves from other people for the duration of the infection. The virus is no longer transmissible when the last scab or crust has fallen off the skin.

Is mpox curable?

Mpox is not curable, but it usually resolves without treatment in a few weeks. The standard treatment is isolation and supportive care. Most people will be treated by a primary care doctor or a specialist in infectious diseases. 

People with mpox can live at home, but they need to stay at home, stay away from other people and pets in the home, regularly wash their hands and objects they touch, use N95 masks, cover all lesions, socially distance, and avoid crowds when going outside the house. Hospitalization is rare, but patients will be isolated from healthcare providers and other patients.

In some severe cases or with people at risk of complications, healthcare professionals may use antiviral drugs, vaccinia immunoglobulin, or smallpox vaccine. People at a higher risk for complications include young children, pregnant women, breastfeeding women, malnourished people, or people with weak immune systems. Severe disease is very rare, but mpox can be fatal when it is. 

Unvaccinated people who have been recently exposed to mpox may be given a smallpox vaccine. If it’s given early enough, the vaccine may prevent an infection or shorten its duration.

How to prevent mpox

The most effective way to prevent mpox infection is a smallpox vaccine. Most people younger than the age of 40 will not have been vaccinated, so at-risk groups can get a smallpox vaccine to gain immunity from mpox. The vaccine of choice is the JYNNEOS vaccine, a smallpox vaccine that does not contain live viruses and does not have many of the adverse effects of earlier vaccines. 

The Centers for Disease Control and Prevention have a national stockpile of smallpox vaccine. The CDC no longer imposes eligibility criteria on the use of the smallpox vaccine, so healthcare providers can provide a two-dose smallpox vaccine to anyone they consider at risk of developing a mpox infection. People who think they’re at risk can request a vaccine without having to prove they belong to an eligible group.

Who should get a smallpox vaccine to prevent mpox? According to the CDC, people in the following high-risk groups should consider getting a smallpox vaccine:

  • Anyone recently exposed to someone infected with mpox

  • Recent sexual contact with someone infected with mpox

  • Healthcare workers or lab workers at risk of exposure to the mpox virus

  • Men who have sex with other men

  • Sex workers

  • Sexual partners of sex workers

  • Anyone with an HIV infection

  • Anyone currently on HIV pre-exposure prophylaxis (HIV PreP)

  • Anyone recently diagnosed with a sexually-transmitted infection (STI)

  • Anyone who anticipates high-risk sexual contact or exposure to an infected person

RELATED: Immunization and vaccination statistics 2023

Most importantly, protect others from infection

People with mpox can live at home, but they should isolate to prevent the spread of mpox:

  • Stay at home except for emergencies or healthcare visits

  • Avoid crowds

  • Avoid contact with other people who share the home

  • Avoid contact with pets or other animals

  • Abstain from all sexual contact and intimacy with other people

  • Wear an N95 mask when around other people or outdoors

  • If possible, cover lesions when around other people or outdoors

  • Regularly wash and sanitize your hands

  • Regularly clean everything you touch: bedding, clothes, towels, door knobs, and anything else that other people might touch—when possible, use disinfectant

FAQs about mpox causes

How does mpox start in the skin?

Mpox can be spread through skin-to-skin contact with someone with a mpox rash. The mpox lesions are full of mpox virus. Once the virus is on the skin, it can enter the body through tiny cuts or breaks in the skin. 

Can you get mpox if you had chickenpox?

The virus that causes mpox is an entirely different virus from the one responsible for chickenpox. People who have had chickenpox or been vaccinated for chickenpox have no more immunity to mpox than those who have never had chickenpox.

Can you catch mpox from a bed?

Bedding is a known transmitter of the mpox virus, but it is not as efficient at passing the virus as skin-to-skin contact or close contact with an infected person. People diagnosed with a mpox infection should not share bedding, towels, or clothing with other people or pets in the home.

What’s next? Additional resources for people with Mpox

Test and diagnostics

Treatments

Scientific studies and clinical trials

Medically reviewed by Leslie Greenberg, MD
Board-Certified Family Physician

Leslie Greenberg, MD, is a board-certified practicing family physician with more than 25 years of doctoring experience. She was a psychology major at Northwestern University near Chicago, then graduated with an MD from the University of Nevada School of Medicine. She completed her family medicine residency at St. Joseph Hospital in Wichita, Kansas. She has trained more than 350 family medicine resident-physicians, been in private practice, and delivered babies for 22 years.

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