Globally, the WHO says there have been 254 laboratory-confirmed cases of infection, including 93 deaths.
Saudi authorities have reported 299 cases, though some are awaiting final confirmation.
"The number of cases sharply increased since mid-March 2014," said Tarik Jasarevic with the WHO in Geneva, adding that most cases were in Saudi Arabia and the neighbouring United Arab Emirates.
As much as three-quarters of the new cases are instances of human-to-human transmission and mainly occurred within healthcare settings, affecting medics and some patients.
"WHO has offered its assistance to mobilise international expertise to Saudi Arabia and the United Arab Emirates to investigate the current outbreaks in order to determine the transmission chain of this recent cluster and whether there is any evolving risk," Jasarevic told dpa via email.
DPA