SINGAPORE (Reuters) - Wealthy Singapore has the funds and expertise to fight Zika, but its warm, wet climate and one of the world’s most densely packed populations mean the mosquito-borne virus may be controlled but not eradicated, at least for years, infectious disease experts say.

People shop for remaining stocks of insect repellent products at a pharmacy in Singapore September 2, 2016. REUTERS/Edgar Su

The tropical city-state, a major global financial and transit hub, is the only known place in Asia with active Zika transmission, according to the U.S. Centres for Disease and Prevention.

So far, the virus has been detected in 189 people since the first locally transmitted infection was reported six days ago, and the areas from where they have been reported are spreading.

In his first public remarks on the outbreak, Prime Minister Lee Hsien Loong said on Thursday: “We must assume that Zika is elsewhere in Singapore.”

Zika can cause serious birth defects when pregnant women are infected, a link discovered last year with the virus’s arrival in Brazil, where its impact has been greatest so far. It is primarily spread by the Aedes aegypti mosquito which also carries dengue, a potentially fatal virus that Singapore authorities have been battling for decades.

Hundreds of specialist workers conduct island-wide inspections for mosquito breeding grounds, spray insecticide and clear stagnant water. Residents of homes where water is allowed to stagnate in flowerpots or elsewhere can be penalised.

Entomologists and infectious disease specialists say Singapore’s experience with dengue has primed authorities to contain Zika. A healthcare system ranked by the World Health Organisation (WHO) as among the top 10 in the world is also in Singapore’s favour.

Singapore, with a “very technologically advanced health system”, was able to identify the disease “very early”, David Heymann, chairman of the WHO’s emergency committee on Zika, said on Friday. “But in other countries where it might enter at some time, that might not be the case.”

But almost daily downpours, average temperatures of 30 degrees Celsius (86 degrees Fahrenheit), large green areas and a population of more than five million people packed in a city that is half the size of Los Angeles, which has a population of 4 million, make Singapore a hospitable area for mosquitoes.

“As demonstrated by the inability to eradicate dengue, the same can be said for Zika virus,” Cameron Webb, a medical entomologist at the University of Sydney, told Reuters.

“This is a mosquito that is not found in the swamps, it’s found in the cities. Mosquito-borne disease is something that we are going to have to manage for many years to come.”

Singapore health ministry officials did not immediately respond to requests for comment on their outlook for Zika.

More than 11,000 cases of dengue have been reported in Singapore so far this year, with the authorities warning the number could exceed 30,000 by year-end, a record high. In 2013, about 22,000 cases of dengue were reported.

Wong Sin Yew, an infectious disease physician at Gleneagles Medical Centre in Singapore, said it was unclear for now whether Zika would become as widespread as dengue. “If we keep having more and more cases, and more and more areas affected, then unfortunately it would indicate the infection has become established,” he said.

STRICT REGULATIONS

The pace at which the infection numbers have risen in Singapore highlights how fast Zika can spread but equally, it also shows the government’s ability to detect the virus.

Such efforts, along with scientific research into possible vaccines and methods to eradicate mosquitoes, could help Singapore contain the disease, experts say.

Singapore already has strict “no breeding” regulations for outdoor areas. The health ministry, in a statement on Friday, said it will be introducing several measures to “enhance the surveillance of the disease and protection of Singaporeans”. It did not give details.

“We also urge all Singaporeans to take the appropriate precautions to prevent mosquito breeding as vector control is critical in preventing transmission and reducing the risk of the virus from taking root in Singapore,” the ministry added.

Even if Singapore could contain the spread of Zika, its status as an international trade and transit hub puts it at risk of further infections. More than 55 million people pass through the airport each year and tourism arrivals topped 8 million in the first half of this year.

“Even if this outbreak of Zika virus was to stop tomorrow, there is no reason why an infected traveller may not bring Zika virus back to Singapore,” said entomologist Webb.

However, there are some indications that these risks could ease in the next few years.

A study published by British scientists in July said the Zika virus infecting countries in Latin America could burn itself out in two to three years, as people develop “herd immunity”, which occurs when a high percentage of a population has become immune to an infection either through developing natural immunity or through vaccinations.