Aug. 3 – An outbreak of pneumonic plague has hit the town of Ziketan in China’s western province of Qinghai, killing two and leading to the full quarantine of its estimated 10,000 residents.

According to the Centers for Disease Control and Prevention (CDC) website, pneumonic plague occurs when the bacteria, Y. Pestis, infects the lungs and spreads from person to person through the air.

The disease is also spread by breathing in Y. pestis suspended in respiratory droplets from an infected 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, reports the CDC.

Y. pestis is easily destroyed by sunlight and drying but will survive for as long as one hour when released into the air. It is the same bacteria that occurs in bubonic plague or the Black Death that killed millions in Europe during the Middle Ages.

The plague has already killed two people. The first victim was a 32-year-old herdsman followed by his 37-year-old neighbor. Eleven people, mostly relatives of the first victim, have been infected and are now being monitored in the hospital. According to the WHO, people infected with pneumonic plague can die within 24 hours of infection if left untreated.

Local authorities are aslo tracking other people who have had contact with the victims. The Qinghai health bureau advises that anyone who has visited the town and its surrounding areas since July 16 and developed a fever or a cough should seek treatment at a hospital, reports the AP.