The Middle East Respiratory Syndrome (Mers) has killed four more people in Saudi Arabia bringing the number of deaths in the past week to 17.

Health officials admit they are worried by the timing, as the kingdom prepares to welcome around two million Muslims for the Hajj next month. Mers infections have been recorded in countries across the Middle East, Europe and Asia.

The virus first emerged in Saudi Arabia in 2012. The World Health Organization (WHO) says many of the recent cases are associated with an outbreak at a hospital in Riyadh.

Mers is caused by a coronavirus, a type of virus which includes the common cold and Sars (severe acute respiratory syndrome). Globally, at least 515 people have died as a result of Mers since September 2012, according to the WHO.