Epidemiology
Plague is caused by infection with the bacterium Yersinia pestis, usually found in small mammals and their fleas. It is not found in the UK, but occurs in several countries in Africa, Asia, South America and the USA. Between 2010 and 2015, there were 3248 cases reported worldwide.
Annually, most human cases occur in Africa, with Madagascar considered to be the most highly endemic country.
See WHO map of global cases.
In Madagascar, a seasonal upsurge in plague cases (mostly the bubonic form) usually occurs each year between September and April. However, in 2017, the season began earlier than usual, is predominantly pneumonic and is affecting areas that do not usually experience plague. These include major urban centres such as Antananarivo (the capital city) and Toamasina (the port city).
Reported case numbers change frequently, but as of 18 October 2017, more than 840 clinically compatible cases (suspected, probable and confirmed) have been reported across 18 of 22 regions.
Two visitors to Madagascar who participated in the Indian Ocean Basketball Club championship in late September were also diagnosed with plague; 1 was a fatal case.
Transmission
Rodents are the main reservoir of infection and people are most commonly infected through rodent flea bites. People are less commonly infected by scratches or bites from infected domestic cats, by direct handling of infected animal tissues, or through laboratory exposure.
An important route of transmission is the inhalation of respiratory droplets or small particles from a patient with pneumonic plague.
Symptomsfata
People infected with plague usually develop acute febrile disease with other non-specific systemic symptoms after an incubation period of 1 to 7 days.
There are 3 main forms of plague depending on the route of infection: bubonic, pneumonic and, more rarely, septicaemic. Other forms of plague disease such as meningitis and pharyngitis are seen but are rare.
Bubonic plague is the most common form of plague and is caused by the bite of an infected flea. The bacteria travel from the site of the bite to a lymph node which becomes inflamed and painful. This is called a ‘bubo’.
Pneumonic plague is the most severe form of plague, and is usually rare. It may result from spread to the lungs from advanced bubonic plague. However, any person with pneumonic plague may transmit the disease via droplets to other people. Untreated pneumonic plague, if not diagnosed and treated early, can be fatal.
Septicaemic plague occurs when infection spreads through the bloodstream. This may be a progression of untreated bubonic plague or can occur as the primary infection. It can cause bleeding, tissue necrosis and shock.
Treatment
Antibiotic treatment is effective against plague, but early diagnosis and treatment is vital to reduce mortality.
Diagnosis
If health professionals suspect a case of plague, they should discuss this with their local microbiology, virology or infectious disease consultant. Expert advice should be sought from the PHE Imported Fever Service.
Notification
All forms of plague are statutorily notifiable. Upon suspicion of a plague diagnosis, the local health protection team should be notified immediately.
Prevention and advice for travellers
All travellers to Madagascar should seek advice 4 to 6 weeks before travelling. They should and be aware of the risks and the potential outcome of infection, and the measures they can undertake to reduce these risks. There is no vaccine to protect against plague.
Prevention measures include:-
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a DEET based insect repellent to protect against flea bites
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avoid contact with dead animals, infected tissues or materials
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avoid close contact with patients with symptoms of pneumonic plague
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avoid crowded areas where cases of pneumonic plague have been recently reported
Unwell travellers who have been to areas where plague occurs, and who may have had contact with rodents or fleas or anyone with symptoms or diagnosed with pneumonic plague, should seek prompt medical advice with details of their travel history and activities.
See NaTHNaC advice.
See WHO factsheet.
