Mpox, formerly known as monkeypox, is a viral disease that has recently garnered global attention due to its widespread human-to-human transmission. The infection is caused by the Mpox virus, an Orthopoxvirus belonging to the same family as the virus that caused smallpox. While the virus is not classified as a sexually transmitted disease (STD), intimate sexual contact has been the dominant route of transmission in the recent global outbreak. Understanding the difference between sexual transmission and STD classification is fundamental to accurately assessing risk.
The Distinction Between Sexual Transmission and STD Classification
Mpox is virologically defined as a zoonotic disease, meaning it historically circulated in animals before occasionally jumping to humans. Traditional STDs are infections whose primary mode of spread relies on the exchange of bodily fluids like semen or vaginal secretions during sex. The Mpox virus is not primarily transmitted through these sexual fluids, even though the virus has been detected in them. The current outbreak’s strong association with sexual activity stems from the prolonged, intimate skin-to-skin contact that occurs during sex. An infection is deemed sexually transmissible when sexual activity is one mode of spread, but an STD classification requires sexual contact to be the central mechanism of transmission. Because Mpox can spread through non-sexual close contact, like prolonged hugging or sharing contaminated bedding, it does not fit the narrow definition of an STD.
Primary Routes of Transmission
The primary route for human-to-human spread of Mpox is through direct, sustained skin-to-skin contact with the infectious rash, scabs, or bodily fluids of a person with the virus. This high-risk exposure frequently occurs during intimate or sexual activities, where even brief contact with a lesion is sufficient for transmission. The lesions themselves contain high concentrations of the virus, making contact with them the highest risk factor. Transmission can also occur via respiratory droplets during prolonged face-to-face contact, typically over several hours. Contact with contaminated materials, known as fomites, poses another risk; this includes touching items like towels, bedding, or clothing that have been in contact with a person’s infectious lesions.
Recognizing the Physical Signs
The initial symptoms of Mpox can be non-specific and resemble a flu-like illness, often appearing between one and three weeks after exposure. This prodromal phase may include fever, headache, muscle aches, fatigue, and notably, swelling of the lymph nodes. Unlike other rash illnesses, swollen lymph nodes are a distinguishing feature of Mpox.
The characteristic rash typically develops one to three days after the flu-like symptoms, though some people develop the rash first or only have localized lesions without a preceding fever. The lesions progress through a distinct series of stages over a period of two to four weeks. They begin as flat, discolored spots (macules), which then become raised, firm bumps (papules).
These firm papules then evolve into fluid-filled vesicles, which subsequently become opaque and pus-filled pustules. The lesions often have a central depression, a feature known as umbilication, and are deep-seated and painful. Finally, the pustules crust over, forming scabs that eventually fall off. A person is considered non-contagious only after all scabs have healed and a fresh layer of intact skin has formed underneath.
Strategies for Protection and Risk Reduction
Vaccination is the most effective proactive measure for individuals who are at risk of Mpox exposure. The JYNNEOS vaccine, a two-dose series, is currently recommended for pre-exposure prophylaxis (PrEP) in high-risk populations, such as men who have sex with men who have had multiple partners in a short period. The vaccine uses a non-replicating virus, making it safer for immunocompromised individuals.
If an individual is exposed to someone with confirmed Mpox, post-exposure prophylaxis (PEP) with the vaccine is recommended, ideally within four days of exposure to prevent the onset of the disease. Beyond vaccination, practical risk reduction involves temporarily avoiding close, sustained physical contact, including sex, with anyone who has a new or unexplained rash. Barrier methods like condoms offer limited protection, as the virus can be on skin outside of the covered area. Anyone who develops symptoms like a rash or fever should isolate immediately and seek testing to prevent further spread.