The World Health Organisation (WHO) will hold urgent talks next week on the often fatal Middle East respiratory syndrome (Mers) virus, after a sharp increase in infections in Saudi Arabia, and the first reported case in Lebanon.

The virus has killed 164 people in the Middle East in the past two years – 126 in Saudi Arabia alone – and the number of cases in numerous countries in the region has risen in recent weeks.

There are fears that secondary infections may be rising, raising the potential for a greater global spread, and stirring memories of the Sars virus, which claimed more than 700 lives in east Asia in 2003, causing mass fear and disruption.

Mers is a coronavirus, like Sars, but is not transmitted as easily. However, more than 30% of people infected with it die, as opposed to a 10% mortality rate with Sars patients. The relatively high death rate has alarmed public health officials across the region, particularly those working with vulnerable Syrian refugee populations.

Another five deaths and 14 new infections were announced by Saudi authorities on Friday.

After a fact-finding mission to Jeddah this week, the WHO said there had been no "significant change in the tranmissibility of the virus". The organisation said most Saudi cases had occurred in healthcare centres and special screening measures and travel restrictions were not yet necessary.

Dr Adam Coutts, a public health researcher working on refugee health, said: "It is not inevitable that refugees will become infected but it is highly likely they will in places such as Jordan and Lebanon.

"It could spread very quickly, given their living conditions, poor sanitation and overcrowding. They are highly susceptible and the least able to recover."

There is no vaccine for Mers and experts are still struggling to establish why it has become so potent. Infected patients typically suffer from a lung infection that causes fever, coughing and breathing difficulties. Some also suffer rapid kidney failure. Most of those who became ill were either hospital staff or patients who had been admitted for some other reason.

"The major issue in a country like Lebanon is that the health system is already under pressure. The ministry of public health is overstretched in terms of a health information system for monitoring health trends and risks," Coutts said.

Lebanon's health minister, Wael Abu Faour, said thermal scanners had been installed at Beirut airport in a bid to detect feverish travellers infected with the virus. He said the one patient so far diagnosed with Mers had been treated and released from hospital.

The WHO said 496 cases of Mers had been recorded in the past two years, 463 of which were in Saudi Arabia. Only 254 were confirmed in laboratories. The virus is thought to have originated from camels.

As well as refugees, other large transitory populations are also thought to be at risk. Saudi Arabia sees millions of Muslim pilgrims from around the world travelling to Islamic holy sites each year. A week ago, Public Health England put out an alert for airline passengers who may have come into contact with a man later diagnosed with Mers who travelled from Riyadh to Chicago via London.

Cases have also been reported in France, Germany, Spain, Italy, Tunisia and Oman.