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Clinical Recognition

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.

Monkeypox Disease

Incubation period

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.

Prodrome

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.

Rash

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.

Enanthem Through the Scab Stage

Stage Stage Duration Characteristics
Enanthem
  • The first lesions to develop are on the tongue and in the mouth.
Macules 1−2 days
  • Following the enanthem, a macular rash appears on the skin, starting on the face and spreading to the arms and legs and then to the hands and feet, including the palms and soles.
  • The rash typically spreads to all parts of the body within 24 hours becoming most concentrated on the face, arms, and legs (centrifugal distribution).
Papules 1−2 days
  • By the third day of rash, lesions have progressed from macular (flat) to papular (raised).
Vesicles 1−2 days
  • By the fourth to fifth day, lesions have become vesicular (raised and filled with clear fluid).
Pustules 5−7 days
  • By the sixth to seventh day, lesions have become pustular (filled with opaque fluid) – sharply raised, usually round, and firm to the touch (deep seated).
  • Lesions will develop a depression in the center (umbilication).
  • The pustules will remain for approximately 5 to 7 days before beginning to crust.
Scabs 7−14 days
  • By the end of the second week, pustules have crusted and scabbed over.
  • Scabs will remain for about a week before beginning to fall off.

Rash resolved

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.

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