Impetigo, the school-sores infection, touched about 140 million people in 2010
Impetigo is a surface skin infection best known for honey-coloured crusts around a child's nose and mouth. It affected about 140 million people worldwide in 2010, most often children aged two to five, and although it usually clears within three weeks even untreated, it passes easily by touch and some strains now resist antibiotics.
Most cases come from the bacterium Staphylococcus aureus, with Streptococcus pyogenes sometimes involved, especially in the common crusting type. The English dermatologist William Tilbury Fox described and distinguished the disease around 1864. Its name is the Latin word for a skin eruption, rooted in impetere, to attack, and in some places it goes by school sores. Before antibiotics, doctors painted lesions with the antiseptic gentian violet, which worked well.
Around 70% of cases are nonbullous. A red spot near the nose or mouth bursts, weeps, and dries into a honey-coloured scab, leaving a red mark that usually fades without scarring; it itches rather than hurts. The bullous form, about 30%, mostly strikes children under two and raises painless fluid-filled blisters on the limbs and trunk. Ecthyma goes deeper, producing painful ulcers that crust into thick grey-yellow scabs and can scar.
Spread happens through direct contact with sores or with people carrying the bacteria in their noses, and nasal colonisation explains why some people get it repeatedly. Symptoms appear 1–3 days after streptococcal exposure and 4–10 days after staphylococcal, while dried streptococci floating in the air cannot infect unbroken skin. Day care, crowding, poor nutrition, diabetes, contact sports and skin already broken by insect bites, eczema or scabies all raise the odds, and it is more frequent in warm climates. More than 162 million children in low- and middle-income countries are affected, with Oceania especially hard hit. In Britain in 1991-1992, children under 4 had an annual incidence of 2.8%, falling to 1.6% across all children up to 15.
Antibiotic creams such as mupirocin or fusidic acid are the usual prescription, with tablets for widespread infection, and one seven-day course clears 95% of childhood cases. Concern about overuse led Britain's NICE in February 2020 to favour a 1% hydrogen peroxide cream for small patches in otherwise healthy people. In Fiji, where impetigo often follows scabies, mass doses of ivermectin are sometimes given to prevent it. Possible complications include cellulitis and a kidney inflammation called poststreptococcal glomerulonephritis; rheumatic fever does not appear to be linked.
Source: Impetigo
