Middle East Respiratory Syndrome (Mers)
Mers is caused by a new type of coronavirus, a type of virus which includes the common cold and Sars (severe acute respiratory syndrome).
First cases emerged in the Middle East in 2012, and the first death in Saudi Arabia in June that year.
It is not known for certain how it is transmitted. It is possible the virus is spread in droplets when an infected person coughs or sneezes.
Patients have a fever, cough and breathing difficulties, but Mers can also cause pneumonia and kidney failure.
Approximately 36% of reported patients with Mers have died - there is no vaccine or specific treatment.