This infection – also known as bubonic plague – is caused by the bacterium Yersinia pestis. In 2013 there were 783 cases reported worldwide, including 126 deaths, the three most endemic countries in recent years being Madagascar, the Democratic Republic of Congo and Peru.

The reservoir for the bacillus is the black rat (Rattus rattus), and less importantly the brown (sewer) rat (Rattus norvegicus). Y. pestis multiplies in the gastrointestinal tract of rat fleas, which may remain infectious for up to six weeks and convey the disease to humans:

Symptoms usually begin 2–8 days after infection with fever, headache, lassitude, and aching limbs. About two-thirds of patients contract bubonic plague in which enlarged glands (BUBOS) appear in the groin, axillae and neck. Haemorrhages may be present beneath the skin causing gangrenous patches and occasionally ulcers, hence the historic term ‘Black Death’. Pneumonic plague is due to person-to-person transmission and results in CONSOLIDATION of the lung; death often ensues on the fourth or fifth day.

Treatment is with antibiotics including tetracycline or doxycycline. Plague remains (together with CHOLERA and YELLOW FEVER) a quarantinable disease. Contacts should be disinfected with insecticide powder; clothes, skins, soft merchandise, etc. which have been in contact with the infection can remain infectious for several months; suspect items should be destroyed or disinfected with an insecticide. Ships from an endemic or epidemic area are checked for presence of rats; the rationale of anchoring a distance from the quay prevents access of vermin. (See also EPIDEMIC; PANDEMIC; NOTIFIABLE DISEASES.)