Plague

What is plague?

Plague, sometimes called Black Death, is a communicable disease that affects rodents, some animals and humans. It is caused by a bacterium called Yersinia pestis. There are three main forms of plague infection: bubonic, pneumonic and septicaemic. Plague in human is a serious disease with a case-fatality ratio of 30% - 60% for the bubonic type, and is always fatal for the pneumonic type when left untreated.

Patients with bubonic plague typically experience a sudden onset of illness characterised by fever, headache, chills, malaise and painful swelling of the affected regional lymph nodes. The swollen lymph node is called a ‘bubo’. This is the common form of plague and is termed bubonic plague.

The infection can progress to septicaemic plague when the Yersinia pestis invade the blood stream. The infection can be spread to other organs and cause serious complications.

Patients with pneumonic plague typically present with fever, chills, headache, body pains, weakness and chest discomfort, cough with blood-stained sputum, difficulty in breathing and may die rapidly if not treated immediately. The patient is highly infectious in this most serious form of plague.

The incubation period of bubonic plague is usually 2 – 6 days while the incubation period for primary pneumonic plague is usually 1 – 4 days.

How does it spread?

Plague is transmitted from an infected animal (mainly rodent) to humans through the bite of infected animal's fleas. People can also contract plague when cuts or other breaks in their skin come into contact with the body fluid or tissue of infected animals, or through inhalation of infected respiratory droplets. Bubonic plague is not usually transmitted directly from person to person unless there is contact with pus from suppurating buboes. Pneumonic plague is highly contagious. It can spread between humans by inhalation of respiratory droplets from an infected person.

Where is plague found?

As an animal disease, plague is found in all continents, except Oceania. Plague epidemics have occurred in Africa, Asia and South America. Since the 1990s, most human cases have occurred in Africa. The three most endemic countries are the Democratic Republic of Congo, Madagascar and Peru.

How is it treated?

Plague patient should be isolated and treated with appropriate antibiotics.

How can you prevent it?

At present, no plaque vaccine is commercially available.

Travellers should avoid visiting plague-affected areas. If travel to such areas is necessary, travellers should take heed of the preventive measures below:-

• Prevent flea bites by wearing long-sleeved shirts and trousers, and applying insect repellent/insecticide. DEET-containing insect repellent can be applied to exposed skin and clothing, while insecticide containing permethrin can be applied to clothing, not the skin. Travellers can refer to the CHP's tips for using insect repellents ;
• Avoid going to rural areas, camping or hunting;
• Never touch rodents, dead animals and their tissues or contaminated materials;
• Avoid close contact with patients, especially those with cough or chest infection;
• Avoid going to crowded areas in regions where cases of pneumonic plague have been recently reported.

In case of sudden symptoms of fever, chills, painful lumps, or shortness of breath with coughing and/or blood-tainted sputum after visiting plague-affected areas, travellers should seek medical care immediately and inform doctor about their travel history.

Travellers should consult doctor immediately after contact or exposure to pneumonic plague patients or other high risk exposures (such as bites from fleas or direct contact with body fluids or tissues of potentially infected animals) for prompt assessment of the need for preventive medication. Travellers should avoid self-administration with antibiotics, unless recommended by medical professionals.