ON SUNDAY, the Saudi health minister, Abdullah al-Rabiah, struck a reassuring tone as the kingdom reported a surge in cases of Middle East respiratory syndrome, a novel coronavirus known as MERS. The minister said he didn’t know why the case count had spiked but maybe it was seasonal. He said he didn’t think it necessary to change preventive measures and insisted that authorities were taking all due precautions.

On Monday, he was fired by King Abdullah. This was a rare public acknowledgment that all is not well. In recent days, the number of people infected has continued to rise. The number of cases in the first third of this year is the same as in all of 2012 and 2013 combined, according to virologist Ian M. Mackay at the University of Queensland in Australia. Most of the cases, but not all, have been in Saudi Arabia. No antiviral or vaccine is known to be effective against the virus, which has killed about one-third of those who have become infected.

The new, acting Saudi health minister, Adel Faqih, immediately struck a different tone. He visited a hospital in Jiddah that has been the epicenter of an outbreak this month and pledged to adhere to “the principles of transparency and disclosure.” For Saudi Arabia, this could be a turning point — none too soon — or it could be another rhetorical flourish. For the sake of global public health, let’s hope that Mr. Faqih means what he says.

Saudi Arabia has a largely closed society, one that won’t be easy to change. Reports about infections have lacked details, and the kingdom does not encourage a free press to poke around. Major uncertainties about the MERS virus persist, including how it spreads, whether it has efficiently begun human-to-human transmission and whether its genetic makeup has evolved. The Saudis must throw open their doors to international scientific inquiry. They are reportedly consulting experts from Germany, Great Britain, the United States and France. We recommend to Saudi leaders the experience of China, which learned painfully in the severe acute respiratory syndrome (SARS) epidemic a decade ago about the high costs of secrecy to human health and welfare.

The World Health Organization reaffirmed Wednesday that “critical information gaps remain” about transmission of the MERS virus and the route of infection. In the recent surge, the WHO estimated that 75 percent of the cases are secondary, meaning that the person was infected by contact with another human, mostly health-care workers and people already in the hospital. That 75 percent estimate is extremely worrisome because it suggests that the virus may be gaining traction in moving from person to person, a prerequisite for a pandemic.

The Saudi king is custodian of the holy sites at Mecca and Medina. Now he also is custodian of a major health crisis. During Ramadan in July and the hajj in October, millions of people will make pilgrimages to Saudi Arabia from around the world. For everyone’s safety and well-being, there must be a move to clarity, cooperation and transparency. Even if MERS does not reach pandemic scale, it must be confronted as if it could.