RIYADH (AFP) - Saudi health authorities announced on Sunday a new death caused by the Middle East respiratory syndrome (Mers) coronavirus, bringing to 53 the number of fatalities in the kingdom from it.

The Health Ministry gave no details on the latest death in the country most affected by the disease that first appeared in the Gulf state in September 2012.

Mers has so far cost 64 lives worldwide, according to a Nov 4 update by the World Health Organisation (WHO).

Experts are struggling to understand Mers, for which there is no vaccine.

It is considered a deadlier but less-transmissible cousin of the severe acute respiratory syndrome (Sars) virus that erupted in Asia in 2003 and infected 8,273 people, 9 per cent of whom died.

Like Sars, Mers appears to cause a lung infection, with patients suffering from a temperature, cough and breathing difficulty.

But it differs in that it also causes rapid kidney failure, and the extremely high death rate has caused serious concern.

In August, researchers pointed to Arabian camels as possible hosts of the virus.