You can recognize potential monkeypox infection based on the similarity of its clinical course to that of ordinary discrete smallpox.
After infection, there is an incubation period which lasts on average 7-14 days. The development of initial symptoms (e.g., fever, malaise, headache, weakness, etc.) marks the beginning of the prodromal period.
A feature that distinguishes infection with monkeypox from that of smallpox is the development of swollen lymph nodes (lymphadenopathy). Swelling of the lymph nodes may be generalized (involving many different locations on the body) or localized to several areas (e.g., neck and armpit).
Shortly after the prodrome, a rash appears. Lesions typically begin to develop simultaneously and evolve together on any given part of the body. The evolution of lesions progresses through four stages—macular, papular, vesicular, to pustular—before scabbing over and resolving.
This process happens over a period of 2-3 weeks. The severity of illness can depend upon the initial health of the individual, the route of exposure, and the strain of the infecting virus (West African vs. Central African virus genetic groups, or clades). West African monkeypox is associated with milder disease, fewer deaths, and limited human-to-human transmission. Human infections with the Central African monkeypox virus clade are typically more severe compared to those with the West African virus clade and have a higher mortality. Person-to-person spread is well-documented for Central African monkeypox virus.
Infection with monkeypox virus begins with an incubation period. A person is not contagious during this period.
- Incubation period averages 7−14 days but can range from 5−21 days.
- A person does not have symptoms and may feel fine.
Persons with monkeypox will develop an early set of symptoms (prodrome). A person may sometimes be contagious during this period.
- The first symptoms include fever, malaise, headache, sometimes sore throat and cough, and lymphadenopathy (swollen lymph nodes).
- Lymphadenopathy is a distinguishing feature of monkeypox from smallpox.
- This typically occurs with fever onset, 1–2 days before rash onset, or rarely with rash onset.
- Lymph nodes may swell in the neck (submandibular & cervical), armpits (axillary), or groin (inguinal) and occur on both sides of the body or just one.
Following the prodrome, lesions will develop in the mouth and on the body. Lesions progress through several stages before falling off. A person is contagious from the onset of the enanthem through the scab stage.
Pitted scars and/or areas of lighter or darker skin may remain after scabs have fallen off. Once all scabs have fallen off a person is no longer contagious.