Fukuda said there wasn't yet proof of the virus' sustained transmission among people.
Last week WHO did declare the world's widening polio outbreaks to be an international health emergency.
Some scientists said while MERS technically meets the criteria for a global health emergency, declaring it as such could confuse the public.
"People might think (WHO) is crying wolf because MERS is still primarily a problem in the Middle East," said Michael Osterholm, an infectious diseases expert at the University of Minnesota who has worked in the Middle East. "But if one of those infected people gets on a plane and lands in London, Toronto, New York or Hong Kong and transmits to another 30 people, everyone will have a different view."
On Wednesday, the Netherlands' National Institute for Public Health and the Environment announced its first case of MERS, a man who became infected during a visit to Saudi Arabia. He is now in isolation at a hospital in The Hague.
Some experts say the spread of MERS is worryingly similar to the 2003 global outbreak of Severe Acute Respiratory Syndrome or SARS, which infected about 8,000 people in 2003, killing nearly 800. MERS is genetically related to SARS.
Scientists are unsure exactly how people are catching MERS but suspect the disease is linked to camels. WHO recommends that people avoid contact with the animals, skip drinking camel milk or using camel urine in traditional medicines and only eat camel meat that has been well cooked.
Dr. Clemens Wendtner, who treated a German MERS patient in Munich last year, said the current spread of MERS should not set off a global alarm. He was not part of the WHO meeting.
"I do not see an international threat or a pandemic (being caused) by MERS," he wrote in an email. He said the spread of MERS to humans was still exceptional and that the disease was mostly affecting animals.
WHO said its expert committee would reconvene in several weeks to consider any new MERS developments.