Saudi Arabia has confirmed seven new cases of Middle East Respiratory Syndrome (MERS), adding up to 36 infections in five days, a sudden increase of a disease that kills about a third of the people infected and has no cure.
MERS, a SARS-like novel coronavirus that emerged in Saudi Arabia two years ago, has infected 231 people in the kingdom, of whom 76 have died, the Health Ministry said on its website.
Meanwhile, another cluster of cases has been detected in the United Arab Emirates, and a Malaysian who was recently in the Gulf has been confirmed as infected, his country said.
MERS has no vaccine or anti-viral treatment, but international and Saudi health authorities say the disease, which originated in camels, does not transmit easily between people and may simply die out.
Health experts have warned, however, that MERS has the potential to mutate eventually.
The number of officially confirmed Saudi cases has jumped suddenly over the past two weeks.
Saudi authorities last week issued several statements aimed at reassuring the public that there was no immediate cause for concern at the latest outbreak and that it had not met international definitions of an epidemic.
On Sunday they said that foreign experts would arrive in the kingdom soon to help the government seek a cure for the disease.
Saudi Arabia, the birthplace of Islam, is expected to receive a surge of pilgrims in July during the faith's annual fasting month of Ramadan, followed by millions more in early October for the Haj.
Last week Malaysian health authorities said a Malaysian citizen had been confirmed as having the disease after he returned from pilgrimage in Saudi Arabia.
Rumours of unreported cases have circulated on Saudi social media feeds in recent weeks. Last week, the kingdom's cabinet asked Saudi news organisations to report only those cases that are officially confirmed by the Health Ministry.
Most of the new infections are in Saudi Arabia's port city of Jeddah, where 30 people have been infected since Monday, seven of them fatally. Another six new cases, one of them fatal so far, were discovered in the capital Riyadh.
Last week, another cluster of cases was discovered in the neighbouring United Arab Emirates, and Yemen reported its first case.
The UAE state news agency WAM said late on Saturday that it had recorded 12 new cases of coronavirus infections that were discovered during "routine checks" on people who had come in contact with infected individuals.
WAM quoted the health authority as saying that the patients were being kept in hospital and "did not pose a danger to the public or to patients". It expected the patients to be rid of the MERS virus within 10 to 14 days.