The earliest known outbreak of the MERS coronavirus infected at least 10 people, a retrospective study has shown. 

Two of those cases, from an outbreak in Jordan in April of 2012, have been previously reported.

An official of Jordan's Ministry of Health revealed the news today in an interview from Amman.

Dr. Mohammad Al-Abdallat says blood samples from 124 people were tested for antibodies to the Middle Eastern respiratory syndrome coronavirus.

He says eight people tested positive, including six people who had been known to be sick at the time of the outbreak, one health-care worker and one household contact of a confirmed case.

The two previously confirmed cases died at the time of the outbreak but were confirmed later using samples that had been stored.

Cluster occurred before new virus recognized 

The study was a joint effort by the Jordanian health ministry and scientists from the U.S. Centers for Diseases Control in Atlanta.

The additional cases, if added to the World Health Organization's global tally, would bring the global count to 72 cases, 38 of which have been fatal.

The cases in Jordan occurred at Zarqa, southwest of Amman. The outbreak happened before the existence of the new virus was recognized. At the time no cause for the cluster of severe pneumonias was identified.

In June of 2012, scientists at Erasmus Medical Centre in Rotterdam, the Netherlands, identified a previously unknown coronavirus — a cousin of the virus that caused SARS — in a sample taken from a Saudi man who had died from a similar pneumonia in a hospital in Jeddah.

The bulk of the diagnosed infections to date have occurred in Saudi Arabia, which on Sunday revealed they had found three new cases in disparate parts of the country.

A recent outbreak of hospital-related cases in Saudi Arabia has racked up several dozen cases in the kingdom's Eastern Province. But in recent days cases have popped up in Taif, near the holy city of Mecca, Jeddah and Riyadh.

Saudi Arabia says four more people have died from a new respiratory virus related to SARS, bringing the total number of deaths to 32 in the kingdom at the center of the growing crisis.

Overall, nearly 40 people have died from the virus since September, mostly in Europe and the Middle East, according to local officials and the World Health Organization.

The Saudi Health Ministry also said on Monday that it confirmed three more cases of the virus, including in a 2-year-old child. Officials are still seeking clues on how easily it is spread between humans.

The new virus is related to SARS, which killed some 800 people in a global epidemic in 2003, and belongs to a family of viruses that most often causes the common cold.