And health officials in Spain have confirmed they have found a second probable case of the new disease, in a woman who attended the Hajj in Saudi Arabia in October.
The press office of Spain's ministry of health said the woman travelled to and from Saudi Arabia with Spain's other probable MERS case. The two women shared sleeping quarters during the trip.
"There is not enough evidence to conclude if there has been person-to-person spread from the first to the second case, or if both cases have been infected from a common source," the ministry said in an email Monday.
The two women have recovered and have been discharged from hospital, the ministry said. Authorities have looked to see if the women infected others, either on the plane on which they journeyed back to Spain or among their contacts in the country. But to date everyone checked has tested negative.
At this point, the two women are classified as probable cases. While they tested positive for the MERS coronavirus, the WHO case definition for confirmed cases requires additional testing.
Spanish authorities, who last week announced they had found the country's first case of MERS, are now awaiting the results of those confirmatory tests.
The WHO has said in the past that it believes probable cases are likely true MERS infections, but in some instances inadequate samples or incorrect testing procedures prevent them from being declared as confirmed. According to the WHO there have been at least 17 other probable MERS infections.
Also on Monday, the Geneva-based global health agency announced that two suspected infections in Kuwait have been confirmed. These two cases — both men, aged 47 and 52 — are the first known cases from that Persian Gulf state. Both men are in critical condition.
Media reports from Kuwait suggested the second man had just returned from Saudi Arabia when he became ill.
To date the WHO has confirmed 157 cases of MERS, 66 of which have been fatal. All the infections are linked back to six countries on the Arabian Peninsula: Jordan, Saudi Arabia, Qatar, the United Arab Emirates, Oman and Kuwait.
Cases have also been diagnosed in Britain, Germany, France, Tunisia, Italy (probable cases), but all were either in people who contracted the virus in a Middle Eastern country or who were infected locally by someone who brought the virus back from a MERS-affected country.