SINGAPORE — While the number of Zika cases has dropped quite sharply in the last two weeks, medical experts here warned against complacency about the disease that looks set to stay.

They also stressed the need to do more research on this relatively unknown disease, especially on its link to microcephaly — where babies are born with abnormally small heads or brain defects — and in developing affordable and rapid test kits.

The number of Zika infection cases has fallen steadily over the weeks. There were 103 cases in the week of Sept 4 to 10, down from 215 cases the week before. Between Sept 11 and 17, there were 62 cases, and the number fell further to 11 for the week of Sept 18 to 24.

Two cases were reported between Sunday and 3pm yesterday. This brings the total number of cases in Singapore to 393, and no new clusters have been identified so far this week.

Dr Lim Chien Chuan from Sims Drive Medical Clinic, located in the initial outbreak cluster, said that the clinic has not seen any new cases over the past two weeks.

“I believe this significant drop in the numbers can be attributed to the effective vector control measures taken by the authorities and the personal protection measures taken by the various individuals living and working around this area.”

However, experts such as Dr Wong Sin Yew, an infectious disease physician at Gleneagles Hospital, cautioned that the Zika virus appears to be establishing itself in Singapore, and others warned that the decline in cases could be temporary — due to factors such as weather and vector control measures — and Singaporeans must continue to stop mosquitoes from breeding in their homes.

Dr Leong Hoe Nam, an infectious diseases expert, pointed out that the cooling weather meant that Singapore is moving away from the traditional dengue peak season, which implies less Aedes mosquito activity and, therefore, less risk of getting a Zika infection, which is spread by the same mosquito.

“I think there will be a period of calm, and the storm will come again ... We should be on our toes. Clearing mosquitoes to this degree or more should be a new norm for all Singaporeans,” Dr Leong said.

Professor Duane J Gubler, founding director of a research programme in emerging infectious disease at Duke-NUS Medical School, said: “Given the potential neurological affects of infection, I would continue to categorise Zika as a high (level) threat until we learn more about the virus and its transmission dynamics.”

His view for more research is shared by Dr Chia Shi-Lu, who said it is hard to manage it in the long term “unless we know the real impact”. Dr Chia, chairperson of the Government Parliamentary Committee for Health, said that this is particularly needed to study the link between Zika and microcephaly.

“Although Zika has been around for decades, why has this link been seen in Brazil only fairly recently? Could there be other factors at play, such as genetic predisposition, or some other environmental factor?” he asked.

Doubts have been cast on the link between Zika and microcephaly in South American countries. Brazilian health officials admitted Zika alone might not be responsible for the birth defect, with data suggesting that socio-economic factors might be involved.

Dr Leong noted that countries have gone about managing the disease in two ways: Allow it to spread unabated and have the epidemic over in 18 months as herd immunity kicks in, or control the mosquito population and the disease will be around a longer time with smaller numbers infected.

For Singapore, the clear strategy is in managing the disease via vector control, and Dr Leong said that one key solution in the fight against Zika is to come up with a test that “allows us to accurately and quickly and cheaply diagnose it” at less than S$50. Current tests cost up to a couple of hundred dollars.

Doctors said that it is unclear how Zika should be categorised in terms of threat level, and how the public health response should be, until there is more information on the virus.

However, Dr Leong noted that Zika appears to be fast to transmit, but low in “devastation” in terms of impact.

He likened it to the H1N1 flu that spread here in 2009, similar in terms of the speed of transmission but it did not kill as many people as initially expected. ADDITIONAL REPORTING BY ILIYAS JUANDA