ONE OF the most worrisome threats from a novel coronavirus first identified in Saudi Arabia in 2012 has been the possibility of rapid and sustained human-to-human transmission. The virus, named Middle East respiratory syndrome, or MERS, is still somewhat mysterious, and much remains unknown about how it spreads. There is no effective vaccine or antiviral treatment. Recent research suggests that camels have been a reservoir for the virus, but many people infected had no contact with camels.

So far, there have been limited examples of transmission from one person to another in close contact, but at the outset, the virus did not appear to be leaping ahead in a way that would threaten an epidemic, as did another coronavirus, the severe acute respiratory syndrome, a decade ago. However, recent disclosures have been disquieting.

In the last week or so, Saudi Arabia and the United Arab Emirates have reported clusters of cases in hospitals and among health-care workers. These clusters could signal a shift in how the virus behaves. On April 13 and 14, the UAE reported a cluster of 10 laboratory-confirmed cases among health-care workers who were screened after one worker died. Saudi Arabia has been struggling against an outbreak in a hospital in Jiddah, where several clusters, including in health-care workers, have been revealed in recent weeks. The total in Jiddah is now more than 40 cases. Also, new cases were reported in recent days in Malaysia, where a man died after returning from a pilgrimage to Saudi Arabia, and in the Philippines, where a paramedic who was infected in the UAE tested positive after he returned home.

It seems logical to conclude that when health-care workers are becoming infected, either they are not following infection-control procedures or the virus is on the move among people. After all, camels are not sitting in hospital waiting rooms.

The World Health Organization says there have been 243 laboratory-confirmed infections from the first case in September 2012 until now, including 93 deaths. Saudi Arabia’s Ministry of Health reports 224 cases and 74 deaths in the kingdom.

Unfortunately, there is far too little information about the virus coming from Saudi Arabia. The Jiddah hospital closed its emergency room temporarily, but the Wall Street Journal quoted a doctor there saying she wished the whole hospital would be closed down until the virus is dealt with.

What happened? We don’t know. There have been reports of Saudi doctors in Jiddah resigning after refusing to treat infected patients. More than a year and a half after the virus was identified, there is a dearth of information about its genetic make-up and a lack of case-control studies that could offer clues about how it spreads. It isn’t comforting that Saudi officials are urging people not to panic. The most reassuring thing they can do is to report openly and honestly what is going on.