SINGAPORE/HONG KONG • Singapore has reported its first suspected case of the mystery Wuhan virus, involving a three-year-old girl from China who had pneumonia and a travel history to the Chinese city of Wuhan.

She has been warded for further assessment and treatment, and isolated as a precautionary measure, said Singapore's Ministry of Health (MOH) yesterday.

The girl was in stable condition, MOH said, noting that she had not visited the seafood wholesale market in Wuhan associated with the cluster of pneumonia cases.

The MOH added that preliminary tests also showed she was positive for respiratory syncytial virus, which is a common cause of childhood pneumonia, and investigations are ongoing to confirm this as the cause.

Singapore is among a number of countries, such as Malaysia and Vietnam, which are carrying out temperature screening on passengers arriving from Wuhan - the capital of China's Hubei province.

In Hong Kong, the authorities activated a newly created "serious response" level yesterday as fears spread about the mysterious infectious disease that may have been brought back by visitors to a mainland Chinese city.

Five possible cases have been reported of a viral pneumonia that has also infected at least 44 people in Wuhan, an inland city west of Shanghai and about 900km north of Hong Kong.

The outbreak, which emerged last month, has revived memories of the Sars epidemic of 2002 to 2003 that started in southern China and killed more than 700 people in the mainland, Hong Kong and elsewhere.

The serious response level indicates a moderate impact on Hong Kong's population of 7.5 million people.

It is the second-highest in a three-tier system that is part of a new government plan launched yesterday to respond to infectious diseases of unknown cause.

The city's health department added another thermal imaging system at Hong Kong's airport on Friday to check the body temperature of arriving passengers.

More staff have been assigned for temperature checks at the West Kowloon high-speed rail station that connects Hong Kong to the mainland.

Hong Kong's Chief Executive Carrie Lam, on a visit to the West Kowloon train station on Friday to review the health surveillance measures, urged any travellers who develop respiratory symptoms to wear surgical masks, seek medical attention and let doctors know where they have been.

The Wuhan health commission said 11 of the 44 people diagnosed with the pneumonia were in critical condition as of Friday.

All were being treated in isolation, and 121 others who had been in close contact with them were under observation.

Most of the cases have been traced to the South China Seafood City market in the suburbs of sprawling Wuhan, where offerings reportedly include wild animals that can carry viruses dangerous to humans.

The commission said the market has been disinfected.

The most common symptom has been fever, with shortness of breath and lung infections in a small number of cases, the commission said.

There have been no clear indications of human-to-human transmission of the disease.

Tests for the exact pathogens and the search for the cause of the infections are under way.

Common respiratory diseases such as influenza, bird flu and adenovirus infections have been ruled out.

The most recent cases in Hong Kong are a 12-year-old girl and a 41-year-old woman who had been to Wuhan in the past 14 days, but did not appear to have visited the food market, the Hospital Authority said.

They were in stable condition and being treated in isolation at Princess Margaret Hospital.

Besides Sars, or severe acute respiratory syndrome, Hong Kong was also hit by bird flu in 1997 and swine flu in 2009.

ASSOCIATED PRESS, THE STAR/ASIA NEWS NETWORK