Two cases are part of what appears to be a growing hospital outbreak in Hofuf, and the other 2 are in Riyadh.
Two cases are part of a hospital cluster in Hofuf, Al-Kharj reported fatal MERS, and Riyadh has a new case.
Officials said 5 super-spreaders caused 83% of cases, and they confirmed a new MERS death.
The 2 patients in Riyadh are a health worker and a contact with a previous case.
The new Riyadh case bears similarities to several recent cases among a group of female roommates who work as janitors.
The new case is in Hofuf, and WHO's director-general said Saudi health authorities have discussed vaccine development with US officials.
Also, a new study found that 47% of Kenyan camels tested had evidence of MERS-CoV antibodies.
The Institute of Medicine (IOM) this week published a report on a 2-day medical countermeasure workshop it held in late March to discuss how to how better develop and deliver medical countermeasures (MCMs) for emerging infectious disease threats, based on challenges that flared up during West Africa's Ebola outbreak.
Researchers also report promising findings in monkeys for a new antiviral, and CDC experts discuss response steps.
For the fourth day in a row Saudi Arabia's Ministry of Health (MOH) has reported a MERS-CoV infection in a foreign woman in her 20s in Riyadh who is not a healthcare worker, while South Korea has quarantined 61 people after a man tested positive for the virus days after he had recovered from the disease.
