HONG KONG - China has sealed off a remote western town of 10,000 people after two people died of pneumonic plague.

Below are some facts about plague:

WHAT IS PLAGUE?

- Plague circulates mainly among small animals and fleas. It is caused by the bacterium Yersinia pestis and can also infect humans.

It is transmitted between animals and humans by the bite of infected fleas, direct contact, inhalation and rarely, ingestion of infectious materials. Plague can be a very severe disease in people, with a mortality rate of between 30 and 60 percent if left untreated.

WHAT DO WE KNOW ABOUT THE BACTERIA?

- Y. pestis is easily destroyed by sunlight and drying. Even so, when released into air, the bacterium can survive for up to one hour. It is endemic in many countries in Africa, the former Soviet Union, the Americas, and Asia.

WHAT ARE ITS SYMPTOMS?

- Infected persons usually start with flu-like symptoms after an incubation period of 3 to 7 days. They experience fever, chills, head and body-aches and weakness, vomiting and nausea. Plague manifests itself in three forms depending on the route of infection: bubonic, septicaemic and pneumonic.

WHAT IS BUBONIC PLAGUE?

- Bubonic plague is the most common form of plague. This occurs when an infected flea bites a person or when materials contaminated with Y. pestis enter through a break in a person's skin. Patients develop swollen, tender lymph glands (called buboes) and fever, headache, chills, and weakness. Bubonic plague does not spread from person to person.

WHAT IS SEPTICEMIC PLAGUE?

- Septicemic plague occurs when plague bacteria multiply in the blood. Patients have fever, chills, prostration, abdominal pain, shock, and bleeding into the skin and other organs. Septicemic plague does not spread from person to person.

WHAT IS PNEUMONIC PLAGUE?

- It is the most virulent and least common form of plague. Pneumonic plague occurs when Y. pestis infects the lungs. This type of plague can spread from person to person through the air. Transmission can take place if someone breathes in aerosolized bacteria, which could happen in a bioterrorist attack.

Pneumonic plague is also spread by breathing in Y. pestis suspended in respiratory droplets from a person or animal with pneumonic plague. Becoming infected in this way usually requires direct and close contact with the ill person or animal.

Pneumonic plague may also occur if a person with bubonic or septicemic plague is untreated and the bacteria spread to the lungs.
TREATMENT AND PREVENTION

- Rapid diagnosis and treatment is essential to reduce complications and risk of death. Effective treatment methods include antibiotics and supportive therapy.

People need to be aware of the areas where plague is active and to take precautions against flea bites and handling carcasses in plague-endemic areas. People should avoid having direct contact with infective tissues or being exposed to patients with pneumonic plague.

Sources: Centers for Disease Control and Prevention, the World Health Organization.

(Reporting by Tan Ee Lyn; Editing by Sanjeev Miglani)

China Medicine