Although Zika's association with microcephaly has not been scientifically confirmed, the World Health Organisation is justified in declaring it a global health emergency, as coordinated global efforts are critically needed in research, vaccine development and international action ("Zika: WHO declares health emergency"; Wednesday).

Zika might not have appeared on our shores yet, but the ominous prospect of newborns afflicted with microcephaly terrifies any parent. As Singapore continues to draw large numbers of overseas visitors and with Singaporeans travelling internationally, a local case seems inevitable.

The burning question of whether Zika becomes endemic and as prevalent as dengue fever remains, as both diseases are spread by the same ubiquitous Aedes mosquito.

One way to curb the spread is to hospitalise suspected patients until blood tests show negative results for the virus. This method proves efficacious only when we can identify cases in the early stages of infection.

Unfortunately, most cases present fairly mild symptoms and pose a real risk of infecting local Aedes mosquitoes, should an infected person get bitten before hospitalisation.

The obvious complementary strategy would be to control the Aedes mosquito population.

However, we have three factors working against us.

First, soaring temperatures alternating with short, intermittent showers caused by the intensifying El Nino phenomenon, enable Aedes larvae to mature more rapidly.

We can see this from rising Aedes breeding indices, with the house index on Aedes breeding having increased four to five times last year.

Correspondingly, the number of dengue cases rose to a record high of more than 11,000.

Based on methods developed by the National University of Singapore (NUS) Saw Swee Hock School of Public Health, we may see close to 30,000 cases this year.

Second, Aedes mosquitoes are fastidious breeders, requiring clean, stagnant water to breed in.

The majority of detected breeding sites are found in homes. Sustainable behavioural change has not occurred in spite of widely publicised campaigns.

Lastly, with households acquiring potted plants and discarding old receptacles for Chinese New Year, we might be inadvertently creating more breeding sites.

We must consciously work together at eliminating Aedes mosquito breeding grounds to fight the current dengue epidemic and prevent the Zika virus from gaining ground.

Chia Kee Seng (Professor)