Two people in China have been diagnosed with plague, the latest cases of a disease more commonly associated with historical catastrophe.

Plague is caused by the bacterium Yersinia pestis and can arise in three forms – a lung infection, a blood infection and a form that affects the lymph nodes, called bubonic plague.
The latter form is perhaps the most famous, and was behind several pandemics including the Black Death of the late middle ages, which is estimated to have killed up to 60% of the European population.
The two new cases being treated at a hospital in Beijing are of the pneumonic form, which is even more serious than bubonic plague.