Mpox: Symptoms, Causes, Treatment & Prevention

What Is Mpox and What Causes It?

Mpox is a viral disease caused by the monkeypox virus (MPXV), a member of the Orthopoxvirus genus that also includes the smallpox virus. The infection causes fever, swollen lymph nodes, and a characteristic skin rash that progresses through several stages over 2-4 weeks before healing.

Mpox was first identified in laboratory monkeys in 1958, giving the disease its original name "monkeypox." However, the virus is actually found primarily in rodents in Central and West Africa, where it has been endemic for decades. The first human case was documented in 1970 in the Democratic Republic of Congo, and since then, the disease has occasionally spread beyond Africa through international travel.

The global outbreak that began in 2022 marked a significant change in the epidemiology of mpox, with sustained human-to-human transmission occurring in countries where the virus had never been endemic. This outbreak primarily affected men who have sex with men, though the virus can infect anyone through close contact. The World Health Organization (WHO) declared mpox a Public Health Emergency of International Concern in response to this outbreak.

There are two distinct genetic clades of the monkeypox virus. Clade I (formerly known as the Congo Basin clade) has historically been associated with more severe disease and higher mortality rates. Clade II (formerly the West African clade) generally causes milder illness and has been responsible for most cases in the global outbreak. Understanding which clade is circulating helps public health officials assess risk and plan responses.

How Does the Virus Work?

The monkeypox virus is a large, double-stranded DNA virus that replicates within the cytoplasm of infected cells. After entering the body through broken skin, the respiratory tract, or mucous membranes, the virus travels to lymph nodes where it multiplies. This initial replication causes the swollen lymph nodes (lymphadenopathy) that are a hallmark of mpox infection.

From the lymph nodes, the virus spreads through the bloodstream (viremia) to other organs and the skin. The characteristic skin lesions develop as the virus infects skin cells, causing the progressive rash that moves through distinct stages. The immune system eventually controls the infection, and the lesions heal over several weeks.

What Are the Symptoms of Mpox?

Mpox symptoms typically begin with fever, headache, muscle aches, back pain, swollen lymph nodes, and fatigue. Within 1-3 days, a characteristic rash develops that progresses through stages: flat spots (macules), raised bumps (papules), fluid-filled blisters (vesicles), pus-filled lesions (pustules), and finally crusted scabs. The entire process takes 2-4 weeks.

The symptom progression of mpox follows a predictable pattern in most cases, though the severity can vary significantly between individuals. Some people experience only a few lesions with minimal discomfort, while others develop hundreds of painful sores that significantly impact daily activities. Understanding the typical symptom timeline helps patients know what to expect and when to seek medical attention.

The prodromal phase (early symptoms before the rash) usually lasts 1-4 days and includes constitutional symptoms such as fever, chills, headache, muscle aches, backache, and profound fatigue. During this phase, lymph nodes typically become swollen and tender, particularly in the neck, armpits, and groin. This lymphadenopathy is an important distinguishing feature that helps differentiate mpox from conditions like chickenpox or herpes.

The Characteristic Rash

The rash is the most recognizable feature of mpox and typically appears 1-3 days after the onset of fever. In the current outbreak, some patients develop the rash before or without experiencing other symptoms. The rash may begin on the face and spread to other parts of the body, or it may first appear in the genital or anal area, depending on how the virus was transmitted.

Each lesion goes through five distinct stages over approximately 2-4 weeks:

• Macules (Day 1-2): Flat, discolored spots that are often reddish or darker than surrounding skin
• Papules (Day 3-4): Raised, firm bumps that may feel like small peas under the skin
• Vesicles (Day 5-7): Fluid-filled blisters that are clear or slightly cloudy
• Pustules (Day 7-14): Lesions fill with pus and become yellowish-white, often with a depressed center (umbilicated)
• Scabs (Day 14-21+): Lesions crust over and eventually fall off, leaving new skin underneath

The lesions are typically deep-seated and firm, distinguishing them from the more superficial blisters of chickenpox. They often have a characteristic "umbilicated" appearance, meaning they have a small dimple or depression in the center. The lesions can be extremely painful, especially when located in sensitive areas like the genitals, anus, mouth, or throat.

Symptoms Specific to Sexual Transmission

When mpox is transmitted through sexual contact, the rash often first appears in the genital or anal area. Patients may experience severe rectal pain, anal bleeding, or pain during bowel movements (proctitis). Lesions in the throat can cause difficulty swallowing (odynophagia). These localized symptoms can be extremely debilitating and may be mistaken for sexually transmitted infections like herpes or syphilis.

How Is Mpox Transmitted?

Mpox spreads primarily through close skin-to-skin contact with an infected person's rash, scabs, or body fluids. This includes sexual contact, kissing, hugging, and prolonged face-to-face contact. The virus can also spread through contact with contaminated materials like bedding, towels, or clothing. A person is infectious from symptom onset until all lesions have completely healed.

Understanding how mpox spreads is crucial for preventing infection and limiting transmission to others. Unlike respiratory viruses that spread easily through the air, mpox requires relatively close and prolonged contact for transmission. The virus is present in high concentrations in the fluid from skin lesions and in respiratory secretions during close face-to-face contact.

Direct contact with the rash, lesions, or scabs of an infected person is the primary mode of transmission. The virus can enter the body through broken skin (including microscopic breaks not visible to the eye), mucous membranes (such as those in the mouth, eyes, nose, or genitals), or the respiratory tract during prolonged face-to-face contact. Sexual contact, including oral, anal, and vaginal sex, facilitates transmission because it involves intimate skin-to-skin contact.

Other Modes of Transmission

While less common, mpox can also spread through:

• Contaminated materials: Bedding, towels, clothing, and other fabrics that have touched an infected person's lesions can harbor the virus
• Respiratory droplets: Prolonged face-to-face contact can lead to transmission through respiratory secretions, though this is less efficient than skin-to-skin contact
• Vertical transmission: Pregnant individuals can transmit the virus to the fetus through the placenta or during delivery
• Animal-to-human: In endemic areas, the virus can spread from infected animals (particularly rodents) to humans through bites, scratches, or handling of infected animals

A person with mpox is contagious from the onset of symptoms until all lesions have crusted over, the scabs have fallen off, and fresh skin has formed underneath. This period typically lasts 2-4 weeks. There is no clear evidence that people without symptoms can spread the virus, though some research suggests the virus may be present in semen for several weeks after lesions have healed.

When Should You See a Doctor for Mpox?

Contact a healthcare provider if you develop a new, unexplained rash (especially in genital or anal areas), have had close contact with someone diagnosed with mpox, or experience symptoms like fever, headache, and swollen lymph nodes along with skin lesions. Seek immediate care for severe symptoms, difficulty breathing or swallowing, or if lesions affect your eyes.

Early medical evaluation is important for anyone who suspects they may have mpox. A healthcare provider can confirm the diagnosis through testing, provide guidance on managing symptoms, prescribe antiviral medication if needed, and help you understand how to prevent spreading the infection to others. Testing is done by swabbing a lesion and sending the sample for PCR (polymerase chain reaction) testing, which can detect mpox virus DNA.

Contact a healthcare provider promptly if you experience:

• A new, unexplained rash or sores anywhere on your body, particularly in the genital or anal area
• Symptoms consistent with mpox (fever, swollen lymph nodes, muscle aches) along with any skin lesions
• Known or suspected exposure to someone with confirmed mpox in the past 21 days
• A rash that resembles mpox after traveling to an area with ongoing mpox transmission

How Is Mpox Diagnosed?

Mpox is diagnosed by testing a sample from a skin lesion using PCR (polymerase chain reaction), which detects the virus's genetic material. A healthcare provider will swab the lesion and send the sample to a laboratory. Test results are typically available within 1-3 days. Clinical examination and symptom history also help confirm the diagnosis.

Accurate diagnosis is essential for appropriate treatment, infection control, and public health reporting. While the characteristic appearance of mpox lesions may lead a clinician to suspect the diagnosis, laboratory confirmation is necessary because several other conditions can cause similar symptoms.

The gold standard test for mpox is PCR performed on material from skin lesions. The healthcare provider uses a swab to collect fluid or cellular material from a lesion, ideally from a vesicle (blister) or pustule. The sample is then tested to detect monkeypox virus DNA. This test is highly sensitive and specific, meaning it accurately identifies true cases while rarely producing false positives.

What to Expect During Testing

When you seek testing for mpox, the healthcare provider will first take a detailed medical history, including questions about your symptoms, potential exposures, sexual history, and travel. They will examine your skin lesions and may also check for swollen lymph nodes. Before visiting a healthcare facility, it's helpful to call ahead so they can prepare appropriate infection control measures.

The swab collection is usually quick but may be slightly uncomfortable, especially if lesions are in sensitive areas. Results typically come back within 1-3 days, though timing varies by laboratory. During this waiting period, you should isolate to prevent potential spread to others.

How Is Mpox Treated?

Most people with mpox recover without specific antiviral treatment within 2-4 weeks. Treatment focuses on managing symptoms: pain medication for discomfort, keeping lesions clean and dry to prevent secondary infection, staying hydrated, and getting adequate rest. For severe cases or high-risk individuals, the antiviral medication tecovirimat (TPOXX) may be prescribed.

The management approach for mpox depends on the severity of illness and whether the patient has risk factors for severe disease. For most healthy individuals, mpox is a self-limiting illness that resolves on its own with supportive care. The immune system effectively clears the virus, and lesions heal without specific treatment.

Supportive Care at Home

Patients with uncomplicated mpox can typically recover at home with the following supportive measures:

• Pain management: Over-the-counter pain relievers like acetaminophen (paracetamol) or ibuprofen can help with fever, headache, and body aches. Lesions, especially in sensitive areas, may require stronger prescription pain medications.
• Wound care: Keep lesions clean and dry. Avoid scratching or picking at lesions, which can lead to secondary bacterial infection or scarring. Cover lesions with clean bandages or clothing to prevent spread.
• Hydration and nutrition: Drink plenty of fluids and eat nutritious foods to support immune function. If mouth or throat lesions make eating difficult, soft foods and liquids may be easier to tolerate.
• Rest: Your body needs energy to fight the infection. Get adequate sleep and avoid strenuous activity.
• Sitz baths: For lesions in the anal or genital area, warm sitz baths can provide relief from pain and help keep the area clean.

Antiviral Treatment

Tecovirimat (TPOXX) is an antiviral medication that can be used to treat mpox. It works by inhibiting a protein essential for the virus to spread from cell to cell. The medication is typically reserved for patients with severe disease, those at high risk for severe disease (such as immunocompromised individuals), or those with lesions in high-risk locations like the eyes or genitals.

Tecovirimat is taken orally twice daily for 14 days. Clinical trials for smallpox showed the medication is safe and effective against orthopoxviruses. Data from the mpox outbreak suggest it may shorten illness duration and reduce symptom severity, though formal clinical trials are ongoing.

What Is the Mpox Vaccine and Who Should Get It?

The JYNNEOS vaccine (also called Imvanex or Imvamune) is approved for mpox prevention and requires two doses given 4 weeks apart. Vaccination is recommended for people at higher risk of exposure, including those with multiple sexual partners or known contact with an infected person. Post-exposure vaccination within 4 days can prevent infection; within 14 days, it may reduce severity.

Vaccination is a key tool for preventing mpox and controlling outbreaks. The JYNNEOS vaccine contains a live but non-replicating modified vaccinia Ankara virus that stimulates an immune response against orthopoxviruses, including monkeypox virus. Because the virus in the vaccine cannot replicate, it is safe for immunocompromised individuals, unlike older smallpox vaccines.

Who Should Consider Vaccination?

Public health authorities recommend mpox vaccination for individuals at increased risk of exposure. This includes:

• Men who have sex with men (MSM) with multiple or anonymous sexual partners
• People who have had a sexually transmitted infection in the past 6 months
• Sex workers and their clients
• People who have had sexual contact with someone from a community experiencing mpox transmission
• Healthcare workers at high risk of occupational exposure
• Laboratory personnel working with orthopoxviruses
• Anyone who has had close contact with someone confirmed to have mpox (post-exposure vaccination)

Vaccination Schedule and Effectiveness

The standard vaccination schedule consists of two doses given 4 weeks apart. Full protection develops about 2 weeks after the second dose. However, even a single dose provides meaningful protection and can reduce the severity of illness if infection occurs. People who received smallpox vaccination in the past may have some existing protection and may only need one dose of JYNNEOS.

Post-exposure vaccination can be highly effective when given promptly after exposure:

• Within 4 days of exposure: May prevent infection entirely
• Within 14 days of exposure: May reduce symptom severity and duration

Vaccine Side Effects

Common side effects of the JYNNEOS vaccine include:

• Pain, redness, or swelling at the injection site
• Muscle aches and fatigue
• Headache
• Mild fever
• Nausea

These side effects are typically mild and resolve within a few days. Serious adverse events are rare.

How Can You Prevent Mpox?

Prevent mpox by avoiding close contact with infected individuals, not sharing personal items like bedding or towels with anyone who has symptoms, practicing good hand hygiene, and getting vaccinated if you're at higher risk. If you have mpox, isolate until all lesions have healed and inform close contacts so they can monitor for symptoms.

Prevention strategies for mpox focus on breaking the chain of transmission by reducing contact with the virus. Because mpox requires close contact to spread, avoiding exposure to infected individuals and contaminated materials is effective. For those at higher risk, vaccination provides an additional layer of protection.

Protective Measures for Everyone

• Avoid close contact with infected individuals: Do not touch the rash, lesions, or scabs of someone with mpox. Avoid kissing, hugging, and sexual contact with anyone who has or may have mpox.
• Do not share personal items: Bedding, towels, clothing, and eating utensils can harbor the virus if used by an infected person.
• Practice hand hygiene: Wash hands frequently with soap and water, especially after being in public spaces. Use alcohol-based hand sanitizer when soap is not available.
• Know the symptoms: Recognizing mpox early allows for prompt isolation and treatment, reducing spread to others.

If You Have Mpox

• Isolate at home: Stay in a separate room from household members if possible. Avoid close contact until all lesions have completely healed.
• Cover lesions: Wear clothing or bandages that cover all rash areas. Wear a well-fitting mask when around others.
• Do not share personal items: Use separate towels, bedding, clothing, and utensils. Wash these items separately with hot water and detergent.
• Notify contacts: Inform anyone who has had close contact with you so they can monitor for symptoms and seek vaccination if appropriate.
• Avoid contact with pets: Animals, particularly rodents and rabbits, can potentially become infected with mpox.

What Are the Possible Complications of Mpox?

Most people recover from mpox without complications, but some may develop secondary bacterial skin infections, scarring, permanent skin discoloration, eye complications (potentially affecting vision), pneumonia, or rarely, encephalitis (brain inflammation). Immunocompromised individuals, children, pregnant people, and those with certain skin conditions are at higher risk for severe outcomes.

While mpox is typically a self-limiting illness that resolves completely, complications can occur, particularly in certain populations. Understanding potential complications helps patients and healthcare providers recognize warning signs early and intervene appropriately.

Skin Complications

Secondary bacterial infection is one of the most common complications. When bacteria enter through broken skin at lesion sites, it can cause cellulitis, abscesses, or more severe infections. Signs of bacterial infection include increased pain, warmth, redness spreading beyond the lesion, pus with a foul smell, or fever that returns after initially improving. Bacterial infections are treated with antibiotics.

Scarring and skin discoloration can occur as lesions heal, particularly if they were deep, numerous, or became infected. Some patients develop permanent hyper- or hypopigmentation (darker or lighter patches of skin) at sites of former lesions.

Eye Complications

Lesions affecting the eyes or eyelids require urgent medical attention. Ocular mpox can cause conjunctivitis (inflammation of the eye lining), keratitis (inflammation of the cornea), and in severe cases, permanent vision loss. Any patient with eye symptoms should be evaluated immediately by an ophthalmologist.

Other Serious Complications

• Proctitis: Severe inflammation of the rectum causing pain, bleeding, and difficulty with bowel movements
• Pneumonia: Lung infection causing cough, shortness of breath, and respiratory distress
• Encephalitis: Brain inflammation causing confusion, seizures, or altered consciousness (rare)
• Sepsis: Overwhelming infection that spreads through the bloodstream

What Is the Outlook for Mpox?

The prognosis for mpox is generally excellent, with most people making a full recovery within 2-4 weeks. The case fatality rate for the Clade II virus circulating globally is less than 0.1% in healthy individuals. Immunocompromised patients and those with severe disease have higher risks but can still recover with appropriate medical care.

The outlook for mpox patients has improved significantly with better understanding of the disease, availability of antiviral treatment, and supportive care strategies. Most patients recover completely without lasting effects, though the weeks of illness can be painful and isolating. Having a support system and maintaining contact with healthcare providers can help patients navigate the recovery period.

After recovery, there is likely some immunity to reinfection, though the duration of this protection is not yet fully understood. Vaccination after recovery is generally not immediately necessary but may be recommended in the future based on evolving scientific understanding.