Two Saudi health workers who had been in contact for patients with Middle East respiratory syndrome (MERS) coronavirus infections are among three new cases reported to the World Health Organisation, the UN agency has said.

The WHO said the female health staff, from the Saudi regions of Assir and Riyadh, both had mild symptoms of MERS, while a third new case in a 67-year-old woman from Riyadh was more severe, with that patient being treated in hospital.

A study by international team of infectious diseases experts who went to Saudi Arabia in May to analyse an outbreak concluded that MERS infection is a "serious risk" in hospitals because it is easily transmitted in healthcare settings.

The virus, which can cause coughing, fever and pneumonia in those it infects and is often fatal, emerged in last year and has since spread from the Gulf to France, Germany, Italy, Tunisia and Britain.

Globally to date, there have been a total of 94 laboratory-confirmed cases including 46 deaths, according to latest WHO figures. The vast majority of cases have been in Saudi Arabia.

The Geneva-based WHO said clinics and hospital caring for patients suspected or confirmed with MERS infection "should take appropriate measures to decrease the risk of transmission ... to other patients, health care workers and visitors".

The United Nations health agency last week issued travel and health advice for the millions of pilgrims who flock to the holy Saudi cities of Makkah and Madinah for the annual haj, saying the risk of MERS infection among them was "very low."