A black plague pandemic that struck the United Kingdom and the rest of Europe last year has left doctors scratching their heads.
How did the infection spread?
What are the symptoms?
The BBC’s health editor, Dr Tom Walker, explains how the pandemic affected doctors.
What is the history of black plague?
Black plague is a highly contagious and lethal infection, caused by the bacterium Clostridium difficile.
It usually occurs in warm, humid conditions.
It can cause mild or moderate symptoms, including a fever, chills, a runny nose and sore throat.
The symptoms are most common in elderly or disabled people.
The disease causes a severe infection, including pneumonia, and usually begins in early to mid-April.
Black plague can spread from infected surfaces to people, especially if they are not immunised.
Where can I get more information?
Read our interactive map of the black plague in England.
Black Plague: A guide to the Black Plague.
The BBC Black Plague programme is available to watch on BBC iPlayer, iPlayer Plus or on mobile devices.
You can also follow BBC Trending on Twitter.
Where to find more black plague information.