Travel agencies have been advised to remove all camel rides from their tour itineraries in the light of the rising number of Middle East respiratory syndrome (Mers) infections around the world. Camels had been identified as one of the hosts that played an important part in transmitting the deadly virus, whose exact source was as yet unknown, University of Hong Kong microbiologist Dr Ho Pak-leung said. But there had been no prevention and control measures to tackle the viral transmission chain since Mers emerged in April 2012, plaguing mainly the Middle East, Ho said. He said local authorities had been lagging behind for several months in their Mers reports, providing no information on whether the virus had mutated in cases found this year. "The recent developments are worrying," Ho said on Commercial Radio yesterday. Travel Industry Council executive director Joseph Tung Yao-chung said camel rides tended to be optional activities not included in tour packages. "It is usually up to the tourist whether to pay for camel rides," he said. EGL Tours executive director Steve Huen Kwok-chuen said they used to provide camel rides in Turkey, Dubai and Egypt, but stopped the activity last year because of fears about Mers. Since the middle of last month, the number of Mers cases has increased sharply, particularly among health-care workers in Saudi Arabia and the United Arab Emirates, World Health Organisation data shows. As of yesterday, the WHO had received reports of 261 Mers cases globally, including 93 deaths. Researchers said in August that they had found Mers-like antibodies in the Arabian camel, meaning the animal was at some point infected with Mers or a closely related virus. In November, Saudi and Qatari authorities announced separately that scientists had found infected camels. "Travel agencies should cancel all camel-riding activities," Ho said. He cautioned that the prevention of Mers was more difficult than severe acute respiratory syndrome, which killed 299 people in Hong Kong in 2003. Ten to 15 per cent of Mers cases tended to be mild, just like the flu, Ho said, but severe pneumonia was also possible, as happened with Sars. He advised maintaining good hygiene as the virus was carried in the urine and faeces of those infected. About 75 per cent of the recent cases were mainly medical workers who were apparently infected by patients, the Centre for Health Protection said. These secondary cases had mild or no symptoms, it said.