The UN health agency will host the emergency meeting on Tuesday to discuss the worrying spread of the virus, which in less than two years has killed 126 people in Saudi Arabia alone, spokesman Tarik Jasarevic told reporters in Geneva.
The WHO's emergency committee has already met four times to discuss the mysterious corona virus, which surfaced in mid-2012.
"The increase in the number of cases in different countries raises a number of questions," Jasarevic said, without giving further details of the aim of the new talks.
The WHO experts will brief reporters at the end of the teleconferenced meeting on Tuesday evening, he said.
The Middle East Respiratory Syndrome coronavirus (MERS-CoV) is considered a deadlier but less-transmissible cousin of the SARS virus that broke out in Asia in 2003, infecting 8,273 people and killing nearly 800 of them.
Like SARS, it appears to cause a lung infection, with patients suffering from a temperature, coughing and breathing difficulties.
But it differs in that it also causes rapid kidney failure.
There are no vaccines or antiviral treatments for MERS, a disease that kills more than 40 percent of those infected and that experts are still struggling to understand.
According to the most recent WHO figures, 496 MERS cases have been detected since September 2012.
The Saudi health ministry says 463 of them have been in the Gulf nation.
MERS cases have also been reported in the United Arab Emirates, Jordan, Egypt, Lebanon and even the United States, with most involving people who had travelled to Saudi Arabia or worked there, often as medical staff.