Hong Kong authorities were testing two people for possible Middle East Respiratory Syndrome (MERS) on Thursday as worry grew across the region about an outbreak in South Korea.
Hong Kong issued a "red alert" advisory on Tuesday against non-essential travel to South Korea, where 14 new cases of MERS were reported on Thursday, taking the total there to 122 cases. South Korea's outbreak that is the largest outside Saudi Arabia.
One case has been reported in China, that of a South Korean man who travelled there after defying a suggestion from health authorities in South Korea that he stay in voluntary quarantine.
Hong Kong's travel industry council has also cancelled 600 tour groups to South Korea, affecting about 12,000 travellers.
In the nearby former Portuguese colony of Macau, authorities have also warned residents against travel to South Korea unless absolutely necessary.
Nine people have died in South Korea of the disease which is caused by a coronavirus from the same family as the one that triggered a deadly 2003 outbreak of Severe Acute Respiratory Syndrome (SARS) that began in China.
There is no cure or vaccine for MERS, which was first identified in humans in 2012. Most of the global cases, which number 1,271 according to World Health Organisation data, and at least 448 related deaths, have been in the Middle East.