Mpox, previously known as monkeypox, is a viral disease that can spread between people through close contact, causing a distinctive rash along with flu-like symptoms. Most people recover fully within a few weeks, but understanding how the illness spreads and recognizing its symptoms early can help protect yourself and others.

Understanding Mpox Around the World

Mpox is caused by the monkeypox virus, which belongs to the same family of viruses that causes smallpox, though mpox is typically much milder. The disease has been present in certain parts of Africa for decades, but recent years have shown that it can spread to other regions of the world. The virus was first identified in laboratory monkeys in 1958, which is how it got its original name, though scientists now understand that the true animal hosts are likely rodents and other small mammals found in African forests.^[2]

There are two main types of mpox virus, known as clades, which are simply different genetic branches of the same virus. Clade I is found mainly in Central Africa and has historically caused more severe illness. Clade II is found in West Africa and tends to cause milder disease. Each of these clades has further divisions called subclades, labeled with letters like Ia, Ib, IIa, and IIb.^[1]

Before 2022, cases of mpox outside of Africa were rare and usually connected to travel or imported animals. However, a global outbreak of clade IIb began in 2022 and continues today, affecting countries around the world. More than 102,000 cases of clade IIb mpox have been reported worldwide since 2022, with 1,700 cases reported in the United States alone in 2023.^[4] Meanwhile, an outbreak of clade I has been affecting the Democratic Republic of the Congo and neighboring countries since 2023, raising international concern.^[2]

The first documented human case of mpox occurred in 1970 in what is now the Democratic Republic of the Congo, when doctors initially suspected the patient might have smallpox. Since smallpox vaccination programs ended after that disease was eradicated, fewer people have immunity that might also protect against mpox, which has allowed the virus to become more clinically relevant in recent decades.^[8]

How People Get Infected

Mpox spreads primarily through close physical contact with someone who has the disease. The virus can be transmitted in several ways, and understanding these routes helps explain why certain precautions are important. Direct contact with the infectious rash, blisters, scabs, or body fluids of an infected person is one of the main ways the virus spreads. This includes touching the lesions themselves or materials contaminated by them.^[1]

Close intimate contact is a significant mode of transmission. This includes activities like cuddling, kissing, or sexual contact. During the 2022 global outbreak, many cases were detected among men who have sex with men, though it’s important to understand that anyone can catch mpox through close physical contact with an infected person, regardless of sexual orientation.^[2]

Respiratory transmission is possible during prolonged, face-to-face contact with someone who has mpox, especially if they have sores in their mouth or throat. Unlike some respiratory viruses that spread easily through the air, mpox requires extended close proximity rather than brief encounters. The virus can also spread by touching objects that an infected person has used, such as clothing, bedding, towels, or eating utensils that haven’t been properly cleaned.^[4]

Animal-to-human transmission happens in regions where the virus exists in wildlife populations. People can catch mpox through bites or scratches from infected animals, handling infected animal meat during preparation, or consuming undercooked meat from infected animals. Various small mammals found in African regions, including certain squirrels, rats, monkeys, and other rodents, can carry the virus.^[8]

Pregnant women who have mpox can pass the virus to their unborn baby through the placenta, a situation called vertical transmission. The virus can also be transmitted to newborns during or shortly after birth. This is concerning because mpox during pregnancy has been associated with serious outcomes including preterm birth, pregnancy loss, and stillbirth.^[1]

Who Is Most at Risk

Anyone can get mpox, but certain groups of people may face higher risk of exposure or more severe illness. Healthcare workers who care for mpox patients without proper protective equipment are at increased risk, as are household members of people infected with the virus. People in regions where mpox occurs naturally in animal populations face risk through contact with infected wildlife.^[12]

During the current global outbreak, cases have been particularly common among men who have sex with men, though this pattern doesn’t mean the disease is exclusive to this group. The virus spreads through close physical contact rather than any particular sexual orientation or identity. Public health experts emphasize that anyone engaging in close intimate contact with multiple partners may have higher exposure risk.^[19]

Certain individuals are more likely to experience severe complications from mpox. Young children, especially those under one year of age, are at higher risk for serious illness. People with weakened immune systems face particular danger, including those with advanced HIV infection, people undergoing cancer treatment, organ transplant recipients, or anyone taking medications that suppress immune function. Pregnant women are also at increased risk for both severe disease and adverse pregnancy outcomes.^[17]

People with certain skin conditions may experience worse outcomes. Those with a history of atopic dermatitis or eczema, conditions that cause chronic skin inflammation and disruption of the skin barrier, are at particular risk. The mpox virus can spread more extensively across damaged skin, leading to more severe and widespread infection.^[4]

Recognizing the Symptoms

The symptoms of mpox typically begin between 3 and 21 days after exposure to the virus, with an average onset around two weeks. The illness usually lasts between two to four weeks total, though the duration can vary between individuals. Not everyone experiences all possible symptoms, and the pattern of symptom development can differ from person to person.^[14]

Many people first experience flu-like symptoms before the characteristic rash appears. These early symptoms can include fever, which may range from mild to quite high. Severe headaches are common, along with muscle aches and back pain that can be quite uncomfortable. A distinctive feature of mpox compared to some other viral illnesses is swollen lymph nodes, which may be felt as tender lumps in the neck, armpits, or groin. People often feel exhausted and may have chills. Some develop a sore throat, runny nose, or cough.^[3]

The rash typically appears one to four days after the flu-like symptoms begin, though some people develop a rash without experiencing other symptoms first. In other cases, people may only have a rash with no fever or other signs of illness. The rash is the most distinctive feature of mpox and goes through several stages over the course of the illness.^[4]

Initially, the rash appears as flat, red spots on the skin. These spots then become raised bumps. The bumps evolve into fluid-filled blisters that look somewhat like chickenpox or pimples. These blisters then fill with pus, becoming what doctors call pustules. Eventually, the pustules crust over and form scabs. Finally, these scabs fall off, leaving fresh skin underneath. This entire process typically takes two to four weeks.^[11]

The location of the rash can vary considerably. During the recent global outbreak, the rash has often started in the genital area, anus, or around the mouth, particularly in cases transmitted through intimate contact. However, it can also begin on the face, hands, or feet before spreading to other parts of the body. Some people develop a widespread rash covering much of their body, while others may have only a few bumps or blisters in one area.^[3]

The rash can appear inside the body as well as on the skin’s surface. Lesions may develop inside the mouth, throat, vagina, or rectum. When present in the rectal area, they can cause inflammation called proctitis, which leads to severe pain, bleeding, or discharge. Genital lesions can cause painful urination. Eye involvement is particularly concerning as it can lead to vision problems if not properly treated.^[17]

Protecting Yourself and Others

Prevention strategies for mpox involve avoiding contact with infected people or animals and, for eligible individuals, vaccination. If someone you know has been diagnosed with mpox or shows symptoms, avoid close contact with them, including sexual and other intimate contact. Don’t share personal items like bedding, towels, clothing, or eating utensils with someone who might have the disease.^[22]

Vaccination is available for mpox and is recommended for certain groups. While no vaccine has been developed specifically for mpox, the smallpox vaccine has been found effective because the viruses are closely related. People at high risk of exposure, such as healthcare workers treating mpox patients, close contacts of confirmed cases, and people who may be exposed through intimate contact with multiple partners, should consider vaccination. Studies suggest smallpox vaccine may be up to 85% effective against mpox.^[24]

In regions where mpox occurs naturally in animal populations, additional precautions are important. Avoid contact with animals that could harbor the virus, including rodents and primates. Don’t handle sick or dead animals, and avoid eating or preparing meat from wild animals without proper cooking. Bushmeat should be cooked thoroughly if consumed at all.^[8]

Regular hand washing with soap and water is a simple but effective prevention measure, especially after being in public spaces or around someone who might be sick. If soap and water aren’t available, alcohol-based hand sanitizer can be used. Avoid touching your face, especially your eyes, nose, and mouth, with unwashed hands.^[16]

If you develop symptoms consistent with mpox, isolate yourself from others as much as possible until you can be evaluated by a healthcare provider. Cover any rash or lesions with clothing or bandages to prevent spreading the virus. Wear a well-fitting mask when you must be around other people. These measures protect household members, pets, and others from potential exposure.^[20]

How the Virus Affects the Body

Mpox is caused by an orthopoxvirus, which means it belongs to a specific genus of large, complex viruses with a double-stranded DNA genome. These viruses are relatively large for viruses, measuring about 200 to 250 nanometers, and have a characteristic brick-like shape when viewed under an electron microscope. They’re surrounded by a protective envelope made of lipoproteins.^[8]

When the monkeypox virus enters the body, typically through broken skin, the respiratory tract, or mucous membranes, it begins infecting cells and replicating. Unlike many viruses that rely heavily on the host cell’s machinery, poxviruses carry most of the genetic instructions they need to reproduce, though they still require the host cell’s ribosomes to translate their messenger RNA into proteins. This self-sufficiency is one reason poxviruses are so successful at infecting cells.^[8]

After initial infection, the virus spreads through the lymphatic system, which is part of the body’s immune system. This explains why swollen lymph nodes are such a common early symptom—the nodes become enlarged as immune cells gather to fight the infection. From the lymphatic system, the virus enters the bloodstream, a phase called viremia, allowing it to spread throughout the body.^[8]

The characteristic rash develops as the virus infects skin cells and triggers an immune response. The progression from flat spots to raised bumps to fluid-filled blisters reflects the virus multiplying in skin cells and the body’s inflammatory response. The fluid inside the blisters contains virus particles, which is why direct contact with the rash is so efficient at spreading infection. As the immune system gains control, the lesions eventually scab over and heal, typically without scarring unless secondary bacterial infection occurs.^[11]

In most healthy individuals, the immune system successfully controls and clears the infection within a few weeks. The body produces antibodies, specialized proteins that recognize and neutralize the virus, providing some degree of immunity against future infections. However, people with compromised immune systems may struggle to control viral replication, leading to more severe and prolonged illness.^[17]

Complications can arise when the virus affects vital organs or allows secondary infections to develop. The virus can cause inflammation of the lungs (pneumonia), heart (myopericarditis), or brain (encephalitis). Bacterial infections can occur in open skin lesions, potentially leading to sepsis, a dangerous whole-body response to infection. Eye involvement can result in corneal scarring and vision loss if not treated promptly.^[10]