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.
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