plague

A depiction of the flight of townspeople into the country to escape from the plague, in 1630. The European epidemics in the years from 1600 to 1750 were among the most devastating in human history. The new waves of the plague which struck northern Italy and Tuscany in 1630 were believed to have killed up to 70% of the population.

Term applied to any epidemic disease with a high mortality rate, but it usually refers to bubonic plague. This is a disease transmitted by fleas (carried by the black rat), which infect the sufferer with the bacillus Yersinia pestis. An early symptom is swelling of lymph nodes, usually in the armpit and groin; such swellings are called ‘buboes’. It causes virulent blood poisoning and the death rate is high.

Rarer but more virulent forms of plague are septicaemic and pneumonic; both still exert a formidable mortality. Outbreaks of plague still occur, mostly in poor countries, but never to the extent seen in the late Middle Ages. Recent outbreaks were reported from the Democratic Republic of Congo (2005, 2006), Algeria (2003), and India (2002). The 2005 outbreak affected 130 people, of whom 57 died.

Transmission Y. pestis persists worldwide in certain wild rodent populations and transmission is mainly by fleas. The flea ingests the bacteria after biting an infected individual. The bacteria then multiply, forming a blockage between the flea's oesophagus and midgut. Prevented from feeding, the hungry flea bites repeatedly and with each bite it regurgitates infected blood into the bite, transmitting the bacteria.

New diagnostic test In 2003 the Institut Pasteur in Madagascar developed a rapid diagnostic test for both pneumonic and bubonic plague antigens that was pilot tested by health workers in 26 sites in Madagascar. The trials were very promising – results appeared after 15 minutes instead of the usual 15 days; the test was sensitive, reliable, and easy to use at the patient's bedside. According to the WHO, the introduction of this test would save lives, as the mortality of the plague depends critically on how rapidly the disease is recognized.

History The first description of the plague dates from 40 BC in Libya. The Roman Empire was swept by plague in AD 251–260. After the Black Death in the 14th century, plague remained endemic for the next three centuries, the most notorious outbreak being the Great Plague of London in 1665, when about 100,000 of the 400,000 inhabitants died. Plague claimed 300,000 victims in Prussia in 1709. In the 1980s and 1990s there were cases of plague in Africa, Latin America, and India.