HONG KONG ALERT

A tourist wearing a mask to prevent contracting Middle East Respiratory Syndrome (MERS) uses her mobile phone at Myeongdong shopping district in central Seoul, South Korea, June 10, 2015. [Photo/Agencies]

MERS 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.

But memories are fresh in Asia of Severe Acute Respiratory Syndrome (SARS), which emerged in 2002-2003 and killed about 800 people worldwide.

MERS is caused by a coronavirus from the same family as the one that caused SARS. It is more deadly than SARS but does not spread as easily, at least for now.

In Hong Kong, a clinic said it was testing two people who had both recently travelled to South Korea. Thirty-one people in Hong Kong who suspected they might have caught the disease have tested negative.

Hong Kong issued a "red alert" advisory on Tuesday against non-essential travel to South Korea while Singapore Airlines said it would waive fees for customers who want to cancel or rebook flights to South Korea.

Despite the fears, only one case has been reported outside South Korea in the current outbreak, that of a South Korean man who travelled to South China's Guangdong province via Hong Kong after defying a suggestion from health authorities in South Korea that he stay in voluntary quarantine.

Among the new South Korean cases was a pregnant woman who contracted the virus in an emergency ward that has been linked to other confirmed cases, the health ministry said.

The woman's pregnancy would limit the scope of treatment available, but she was in stable condition, the ministry said. The woman's parents had previously tested positive for MERS.