By Aradhana Aravindan and Ben Blanchard

SINGAPORE/BEIJING (Reuters) – China intensified its checks on people and goods arriving from Singapore on Thursday, as an outbreak of the Zika virus in the small city-state was confirmed to have spread to at least one person in neighboring Malaysia.

Singapore is the only Asian country with an active transmission of the mosquito-borne Zika virus, which is a particular risk to pregnant women, according to the U.S. Centers for Disease Control and Prevention.

Authorities in Singapore, a leading regional financial center and busy transit hub for people and cargo, reported the first locally-transmitted Zika infection on Saturday, with the number of cases rising to 115 by Thursday – half of whom were foreigners, mainly from China, India and Bangladesh.

Malaysia confirmed its first case of Zika infection, in a woman who had recently visited Singapore.

“We have been tracking Zika for a while now, and knew it was only a matter of time before it reached Singapore,” Singapore Prime Minister Lee Hsien Loong posted on his Facebook page. “Our best defense is to eradicate mosquitoes and destroy breeding habitats, all over Singapore.”

The United States, Australia and other countries have warned pregnant women or those trying to conceive not to travel to Singapore.

The outbreak and travel warnings come just two weeks before the Singapore F1 motor-racing Grand Prix, a major sporting and tourist draw. Race promoter Singapore GP has said planning for the event is going ahead “as per normal”.

Singapore’s Tourism Board has said it is premature to consider any impact on the tourism industry, stressing the tropical city-state remains a “safe travel destination”.

More than 55 million people pass through Singapore’s Changi airport each year. Tourism arrivals topped 8 million in the first half of this year, around 1 million more than a year ago.

“NEGATIVE IMPACT”

China is trade-dependent Singapore’s top overseas market, and the Zika outbreak coincides with a dip in overall exports and slowing economic growth in both countries.

“If this continues, certainly it will have a negative impact, but it’s hard to quantify in percentage terms or dollar value,” said Francis Tan, an economist at United Overseas Bank in Singapore.

The Zika virus, which has spread through the Americas and the Caribbean since late last year, is generally a mild disease but has been linked to microcephaly – a severe birth defect in which babies are born with abnormally small heads and underdeveloped brains.

The World Health Organization, which has declared Zika an international public health emergency, is holding a regular meeting of its Zika emergency committee on Thursday to review the spread of the disease.

Singapore authorities said late on Wednesday they found some new Zika cases beyond the cluster area where it had initially been detected. They also confirmed a first Zika case in a pregnant woman in the country.

On Thursday, Singapore said half of the cases found so far involved foreigners – including 23 Chinese nationals, 15 Indians and 10 Bangladeshis – adding that most patients had recovered. Many of the foreigners are believed to be among the hundreds of thousands of migrant workers who work in Singapore’s construction and marine industries.

Malaysia, which has two land border crossings with Singapore, asked those going to the city-state to use mosquito repellent and to cover up to avoid bites. Tens of thousands of people travel between the two countries daily.

Indonesia has also stepped up protective measures following the Singapore outbreak, intensifying checks on arrivals from Singapore, introducing thermal scanners and posting paramedics at airports and border checkpoints.

Zika is carried by mosquitoes, which transmit the virus to humans, though a small number of cases of sexual transmission of the virus have been reported in the Americas. A case of suspected transmission through a blood transfusion in Brazil has raised questions about other ways in which Zika may spread.

There is no vaccine or treatment for Zika, which is a close cousin of dengue and chikungunya and causes mild fever, rash and red eyes. An estimated 80 percent of people infected have no symptoms, however. The WHO has also linked Zika to Guillain-Barre, a rare neurological syndrome that causes temporary paralysis in adults.

(Additional reporting by Joseph Sipalan and Rozanne Latiff in Kuala Lumpur; Writing by Miral Fahmy; Editing by Ian Geoghegan)