Plague is an infectious disease caused by a bacterium called Yersinia Pestis.
The disease is transmitted to humans by the bite of an infected flea. The animal reservoir is usually a rodent. In Europe during the Middle Ages, plague was responsible for more than 200 million deaths in three major pandemics. The name still conjures fears despite the fact we now have modern antibiotics able to successfully treat the disease.
Failure to recognise the symptoms and delayed treatment can still result in serious illness or death.
Human disease is mostly bubonic plague where the infected individual presents with swollen lymph nodes (often in the groin). Gastrointestinal symptoms are common. Pneumonic plague may follow respiratory exposure to droplets from an infected person. This form is much less common but has a much higher mortality (>50%) versus 5% for bubonic plague.
Plague exists in the natural in wild rodents in Asia, Africa and the Americas. There are occasional reports in humans. About 5-7 cases of plague are reported annually in the USA. Domesticated dogs and cats may carry infected fleas into the home. The last recorded outbreak of local plague in the UK was reported in 1918 and no cases, either local or imported, have been reported since then. No cases were reported in travellers in a large outbreak in India in 1994 when over 5,000 suspected cases and 53 deaths were reported.
Approximately 1,500 cases are reported to the World Health Organisation (WHO) annually with mortality rates less than 10%. Very few cases are reported in major cities. Most occur in small rural villages in agricultural areas where rodents and farm produce co-exist. According to the WHO, the three most endemic countries globally are the Democratic Republic of the Congo, Madagascar and Peru.
Australia does not have endemic plague.
Plague vaccine is not commercially available in most countries. A vaccine has been available in the past and its use is limited to laboratory workers involved in plague research. It has limited efficacy.
