Mpox (formerly called monkeypox) typically starts with flu-like symptoms about 8 days after exposure, though this incubation period can range anywhere from 3 to 21 days. During that window, you feel completely fine. Then the first signs appear, usually before any rash, giving you an early signal that something is off.
What Happens Inside Your Body First
After the virus enters through broken skin, mucous membranes, or respiratory droplets, it begins replicating quietly at the site where it got in. From there, it travels to your nearest lymph nodes, which act as immune system checkpoints. The virus multiplies in those lymph nodes and then enters your bloodstream, spreading to other organs. This silent phase is the incubation period, averaging about 8 days based on data from both the 2022 global outbreak and earlier outbreaks going back decades.
You’re not contagious during most of this phase, and nothing feels wrong. The trouble starts once the virus has spread widely enough to trigger your immune system’s alarm response.
The First Symptoms You’ll Notice
Before any rash appears, most people go through a prodrome, a short stretch of general illness that can last one to four days. The CDC lists the typical early symptoms as fever, fatigue, headache, sore throat, cough, and swollen lymph nodes. Muscle aches and back pain are also common early complaints.
Swollen lymph nodes are one of the more telling early signs. They most commonly show up in the neck, armpits, or groin and can feel tender or noticeably enlarged. This feature is especially useful for distinguishing mpox from chickenpox and other rash illnesses, which don’t typically cause prominent lymph node swelling.
Not everyone follows this script, though. During the 2022 outbreak, some people developed a rash as their very first symptom, with little or no fever beforehand. Others had only a single sore in the genital or anal area and no body-wide symptoms at all. So while the classic pattern is flu-like illness followed by rash, the virus doesn’t always announce itself that way.
How the Rash Develops
The rash is the hallmark of mpox, and it follows a predictable sequence of stages. It begins as flat, discolored spots on the skin. Within a day or two, those spots rise into firm, round bumps. The bumps then fill with clear fluid, becoming blister-like, before the fluid turns cloudy and pus-filled. Finally, the lesions crust over into scabs that eventually fall off. The entire cycle from first spot to scab separation takes roughly two to four weeks.
All the lesions in a given area tend to be at the same stage at the same time, which is another way doctors differentiate mpox from chickenpox (where old and new lesions appear side by side in different stages). The spots can be painful or intensely itchy, and lesions near the eyes, mouth, genitals, or anus can be particularly uncomfortable.
Where the rash shows up first depends partly on how you were exposed. In the 2022 global outbreak, many cases started with sores in the genital or anal region, sometimes with only a handful of lesions total. Classically, mpox rash spreads across the face, palms, and soles of the feet before covering larger areas of the body. Both patterns are legitimate presentations of the same virus.
How Clade Affects What You Experience
There are two major genetic branches of the mpox virus, and they cause somewhat different illnesses. Clade II, the strain responsible for the 2022 global outbreak, tends to cause milder disease. The rash may be limited to a few sores around the mouth or genital area, and deaths have been very rare in the United States.
Clade I, which has circulated primarily in Central Africa, is more likely to cause severe illness. The rash can cover much of the body, including the face and torso. Mortality rates for Clade I have ranged from 1 to 10 percent, with the highest risk in children and people with weakened immune systems. In the Democratic Republic of the Congo, over half of reported Clade I cases have been in children, who tend to develop more severe disease than adults. A newer sublineage called Clade Ib has drawn international concern because of its ability to spread through close contact in ways that mirror the 2022 Clade II outbreak.
Signs That Set Mpox Apart
Because mpox starts with generic symptoms like fever and fatigue, it’s easy to confuse it with the flu, chickenpox, herpes, or syphilis in the early days. A few features help distinguish it:
- Swollen lymph nodes are common in mpox but unusual in chickenpox and smallpox.
- Lesions at the same stage in a given area suggest mpox rather than chickenpox, where crops of lesions appear at different times.
- Deep, firm bumps that feel like they’re embedded in the skin, rather than superficial blisters, are characteristic of mpox.
- Location of the first sore in the genital, anal, or oral area, especially after close physical contact with someone who had similar symptoms, raises the likelihood considerably.
The World Health Organization considers someone a suspected case if they develop an unexplained acute rash or swollen lymph nodes, particularly with lesions in the genital or anal region, and common causes like herpes, syphilis, and chickenpox don’t fully explain the picture. A confirmed diagnosis requires a lab test, usually a swab of a lesion sent for PCR testing.
When You Become Contagious
You can spread the virus from the time your first symptoms appear until every last scab has fallen off and fresh skin has formed underneath. The lesions themselves are the most contagious element: the fluid inside is packed with virus. Close skin-to-skin contact, especially with open sores, is the primary route of transmission. Sharing bedding, towels, or clothing that touched active lesions can also spread it. Large respiratory droplets during prolonged face-to-face contact are a less common but documented route.
The contagious window typically lasts two to four weeks, matching the time it takes for all lesions to fully heal. Isolation is recommended for the entire duration, which can feel long, but it’s the most reliable way to prevent passing the virus to someone else.