Plague

• Introduction
• Epidemiology
• Risk for travellers
• Transmission
• Signs and symptoms
• Treatment
• Prevention
• References
• Reading list
• Links

Introduction

Plague is a zoonotic infection with a spectrum of clinical manifestations caused by the Gram negative bacterium Yersinia pestis. The disease is most commonly transmitted by fleas, with several species of wild rodent being the natural hosts, although other mammals such as cats and dogs can also become infected. Plague is still reported consistently from several countries in Africa, Asia, South America and rural parts of the USA. Plague has spread from China at the end of the last century and extended to the rest of Asia, Europe, Africa and North and South America. In 1994 India reported more than 800 cases of pneumonic plague; however cultures did not confirm the presence of plague.

Epidemiology

(Data from the Travel Health Surveillance Section of the Health Protection Agency Communicable Disease Surveillance Centre)

Global Epidemiology

History

The first possible occurrence of plague was recorded in biblical times in 1320 BC and is described in the Old Testament book of Samuel. There have been three recorded worldwide pandemics throughout history. The first pandemic that was reported as being attributable to plague was the Plague of Justinian in 542-6 AD and was spread across Africa, Asia and Europe, killing millions (although exact details of this pandemic are unknown). The most famous plague pandemic however, occurred in the middle of the fourteenth century and was known as the Black Death. This pandemic was reported to have possibly originated from central Asia in 1346, spread westwards to Europe along the Silk Road, reaching the southern coast of England in 1348. The disease then spread northwards to the rest of the British Isles, northern France, Germany, and Scandinavia in 1349. The pandemic persisted for seven years in Europe but lasted for no longer than five or six months in any one region or town. It has been estimated that 25 million people worldwide died during the Black Death, from both bubonic and pneumonic forms of the disease.

Plague epidemics continued to occur in Europe after the Black Death but to not such a large scale. During the seventeenth century, there was The Great Plague of London, in which 70,000 people died from an estimated population of 460,000. The third pandemic began at the end of the nineteenth century in southern China killing approximately 100,000 and then spreading worldwide from seaports in Canton and Hong Kong, eventually killing 10 million by the 1920s.

Current picture

Plague naturally occurs in rodents, lagomorphs (rabbits and hares), and squirrels in many countries within tropical and sub-tropical areas of the world. In particular, northern and southern Africa, some parts of north America, and central, south and southeast Asia have reported cases of plague between 1970 and 2003 [1]. Plague is currently a notifiable disease under the International Health Regulations; the total number of cases of plague reported to the World Health Organization between 1989 and 2003, was 38,310 including 2845 deaths from 25 countries [2]. In 2002, the total number of reported plague cases in 13 countries was 1,925, of which 177 were fatal. In 2003, nine countries reported 2,118 cases including 182 deaths. These figures indicate a decrease when compared with the annual average figures (2,895 cases, 206 deaths) for the previous ten years (1992-2001), when 28,956 cases with 2064 deaths were reported from 22 countries. During that decade, 80.3% of cases and 84.5% of deaths were reported from Africa. Cases of plague have been reported nearly every year during that same period from eight countries: Democratic Republic of the Congo, Madagascar, United Republic of Tanzania, Peru, United States, China, Mongolia, and Viet Nam.

Since 1994, there have been three new outbreaks of human plague that occurred in three countries 30-50 years after no cases being reported. The first was in India in 1994, where over 5000 cases were reported resulting in disruption to travel and international trade, with devastating economic effects [3]. An outbreak of bubonic plague involving six cases occurred in Indonesia in 1997 [4]. The third was an outbreak in Algeria in 2003, where ten confirmed cases and one probable case were reported [5].

 

Plague in travellers from England and Wales

Plague does not occur in the UK. The last outbreak of indigenous plague in the UK was recorded in 1918 [6]. No cases are known to have been reported in the UK since then, neither indigenous nor imported.

 

Risk for Travellers

Plague is a rare disease in travellers. In the 1994 epidemic in India several states were involved but no travellers were affected. The risk is highest in those who may have contact with rodents such as field workers.

Transmission

Plague bacteria are carried in the gullet of fleas. The gullet becomes blocked by replicating bacteria, which forces the fleas to regurgitate bacteria while feeding on mammals.

The most important hosts for transmission of plague to man are the domestic black rat and the brown sewer rat. The disease is maintained in rural areas by hosts that include gerbils, squirrels and prairie dogs.

Direct spread between humans is possible in pneumonic forms of the disease by droplet infection.

Signs and Symptoms

Plague can have several clinical manifestations; bubonic plague is the most common. Other manifestations include septicaemic plague without bubo, pneumonic plague (primary or secondary to bacteraemia), meningitis, and pharyngitis.

Following an incubation period of two to five days, plague has a sudden onset of fever, chills, headache, malaise, myalgia and nausea. In bubonic plague, bacteria move from the site of inoculation to regional lymph nodes that enlarge and become painful swellings known as bubos. The bacteria can spread via the bloodstream resulting in septicaemia that if untreated, can lead to a rapid deterioration and death. In pneumonic plague the bacteria either infiltrate the lungs causing primary pneumonia, or secondary pneumonia occurs after bacteraemic spread in bubonic plague. This causes severe shortness of breath and cough with blood stained sputum, leading to respiratory failure. Pneumonic plague is rapidly fatal if untreated.

Treatment

Diagnosis of plague is made by detection of the bacillus in an aspirate of a bubo, sputum or blood. Prompt treatment is important to achieve clinical cure; therefore antibiotics are usually commenced on clinical diagnosis. The drugs of choice are streptomycin, tetracycline or chloramphenicol.

Prevention

Plague vaccine is no longer available in the UK and is rarely indicated. When needed for exceptional circumstances, e.g. for high- risk laboratory workers, it can be imported from the United States. Travellers should take steps to avoid contact with rodents by disposing of rubbish. Insect bite avoidance measures should be employed such as the use of repellent on skin and insecticide on clothing, to discourage flea bites.

Tetracycline, doxycycline or trimethoprim-sulphamethoxazole can be used as chemoprophylaxis in persons who will be in close contact with plague pneumonia.

References

1. Centers for Disease Control and Prevention (CDC). CDC Plague Home page [online] [cited 4 February 2005]. Atlanta: CDC; 10 November 2003. Available at http://www.cdc.gov/ncidod/dvbid/plague/index.htm .

2. Anon. Human plague in 2002 and 2003. Wkly Epid Rec 2004; 79 (33): 301-8. Available online at http://www.who.int/wer/2004/en/wer7933.pdf .

3. Matteelli A, Saleri N. Respiratory Diseases. In: Keystone JS, Kozarsky PE, Freedman DO, Nothdurft HD, Connor BA. Travel Medicine. Philadelphia: Elsevier Ltd.; 2004.

4. Anon. Human plague in 1997. Wkly Epid Rec 1999; 74 (41): 337-48. Available online at http://www.who.int/docstore/wer/pdf/1999/wer7441.pdf

5. WHO. Plague in Algeria - Update 2. Disease Outbreak News [online] [cited 4 February 2005] Geneva: WHO; 2003. Available at http://www.who.int/csr/don/2003_07_10/en/ .

6. Health Protection Agency (HPA). General information - plague. [online] [cited 4 February 2005]. London: HPA; 2003. Available at http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAutoList

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Reading List

Cliff A, Haggett P, Smallman-Raynor M. The Classic Plagues. In: World atlas of epidemic diseases. New York: Arnold; 2004.

Smith MD. Plague. In: Cook GC, Zumla A (editors.) Manson's Tropical Diseases 21st edition. 2003 Elsevier Science Ltd Edinburgh: Elsevier Science Ltd; 2003

Links

Health Protection Agency http://www.hpa.org.uk/webw/HPAweb&Page&HPAweb
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