Geneva: International health experts held urgent talks on the Middle East coronavirus (Mers-CoV) on Tuesday amid concerns about larger numbers of milder infections possibly going undetected, the World Health Organisation (WHO) said.

The United Nations agency announced last Friday that it was forming an emergency committee to prepare for a possible worsening of the Sars-like virus.

The committee is to assess whether the outbreak constitutes a “public health emergency of international concern”, and can recommend measures to try to contain its spread, such as travel restrictions.

Margaret Chan, the director-general of WHO, said she decided to convene the committee for just the second time to help protect travellers to the annual Haj pilgrimage against the coronavirus that’s killed 38 people in Saudi Arabia.

The 15-member committee, which includes Saudi Arabia’s deputy health minister Ziad Memish and health officials from six other predominantly Muslim countries, met via teleconference to decide whether Mers-CoV or Middle East Respiratory Syndrome Coronavirus represents a public health emergency of international concern. Chan last convened the committee to battle the 2009 global flu pandemic.

A further closed-door session was set for Thursday, one official said.

The novel coronavirus emerged in Saudi Arabia in April 2012.

“Millions of people are going to Makkah and to Madinah: we cannot stop that and we should not stop that,” Chan said in an interview at the WHO’s headquarters in Geneva on Tuesday. “We need to say that it’s OK to go, but these are the measures that governments must take.”

The previously unknown virus has sickened 80 people and killed 45 worldwide, according to the WHO. While most cases have been detected in Saudi Arabia, infections in the UK, France, Germany and Italy have sparked concern of a global outbreak like 2003’s Sars epidemic. Scientists still don’t know where the new virus came from or how’s it’s spreading.

That prompted Chan to say at the WHO’s annual World Health Assembly in May that the virus is her “greatest concern”. While the pace of new infections has slowed since then, she said she wants to be prepared in case it returns.

“Am I still worried? The answer is yes,” she said. “Eventually I hope the disease will burn out. But what if it doesn’t? We should always have plan A, plan B and plan C.”

Chan, who fought Sars or severe acute respiratory syndrome as director of health in Hong Kong a decade ago, said the lessons from that outbreak may have helped prevent Mers from becoming worse.

“We have learned from Sars: if you limit the population’s exposure, the disease will die out on its own,” she said. “We just hope that this is also what we are seeing. I have learned from too many occasions in the last 40 years in public health. I never let down my guard.”

Eight of the latest infections in Saudi Arabia were reported to be in people not displaying any symptoms of the disease, which can cause coughing, fever and pneumonia, the WHO said.

Half of them were female health workers, and the rest children under 15 who had contact with confirmed cases.

“The recent mild and asymptomatic cases raise concerns about the possibility of large numbers of milder cases going undetected,” the WHO said in a statement posted on Tuesday.

“While it is clear that human-to-human transmission does occur, it is not clear whether transmission is sustained in the community,” it said.

The current pattern of disease could be consistent either with ongoing transmission of the virus in an animal population/swith “sporadic spillover” into humans resulting in small clusters of people becoming infected, or “unrecognised sustained spread of the virus among humans with occasional severe cases”.

WHO experts said last month that countries at risk from Mers should put in place plans for handling mass gatherings, but the agency has stopped short of recommending restrictions on travel such as checks at airports and other entry points.

Saudi Arabia’s health ministry announced at the weekend that two more people had died of the virus, shortly before the Ramadan fast when many pilgrims visit.