More than a dozen extra health screeners are on high alert at Chek Lap Kok airport this month looking for anyone returning from Saudi Arabia who may show signs of the deadly human Mers virus, which has already claimed 60 lives and comes from the same family as Sars.

Of the 139 cases of Middle East Respiratory Syndrome, most have occurred in Saudi Arabia, raising global health concerns this month as millions of pilgrims flocked to the Muslim holy city of Mecca for the annual haj, which finished on Thursday.

The haj is considered one of the biggest religious gatherings in the world, with more than two million pilgrims making the journey this year.

About 200 Muslims from Hong Kong are currently in Mecca, most of whom are travelling in one of four specially organised groups. In September, health officials gave talks on Mers to the four groups, detailing signs and symptoms of the virus, incubation period and how to avoid it.

Nine local travel agencies also attended Mers briefings organised by the Port Health Office, with tour guides advised to encourage groups to be vigilant about their health on the trip.

Most pilgrims will stay for another week or two to visit other holy locations near Mecca, with those from Hong Kong expected to return home later this month.

This year, the Saudi government restricted the number of overseas Muslims allowed to attend the haj, but said this was not due to Mers but rather reduced space at the Grand Mosque because of construction.

Every year, countries are given a quota of 1,000 pilgrims per one million Muslims. That was cut this year but there is no quota for Hong Kong given its relatively small Muslim population.

Meanwhile, health chiefs in Hong Kong said they were closely monitoring the most recent case of Mers, involving a 61-year-old man from Qatar who tested positive for the virus after he was admitted to hospital on October 11.

Since April, an extra 15 health assistants have joined the team of 70 airport screeners who conduct random temperature checks of travellers from the Arabian Peninsula and neighbouring countries.

"The Centre for Health Protection will continue its surveillance mechanism at public and private hospitals, with practising doctors at the airport for any suspected case of Mers," a spokesman said.

All pilgrims must go through a health check before they are given a visa for the haj.

At a talk on Wednesday about the haj and its relevance to Hong Kong Muslims, anthropology lecturer Paul O'Connor said, "There's been a lot of concern about this virus". He said: "[The] haj is a place where we are always concerned about health."

Often, pilgrims suffered from the "haj cough" when they got home, he said.

Last year, one of the imams who led a group of pilgrims returned to Hong Kong and was admitted to hospital for observation because he was ill.

There are about 260,000 Muslims living in Hong Kong, the majority of whom are Indonesians. About 30,000 are ethnic Chinese Muslims.