Contagious infection due to the mite, Sarcoptes scabei.
More common in crowed living conditions (eg nursing homes)
Female burrows into skin and lays up to 40 eggs (female dies in 1-2 months), hatch in 1 week, reach maturity in 3 weeks cycle starts again
Characterised by insidious onset of pruritic (becomes intense), pustules, vesicles and linear burrows. Itch is worse at night