SINGAPORE: As the Zika virus spread from one area to a new potential cluster at Bedok North Avenue 3, medical experts told Channel NewsAsia that it may become increasingly difficult to contain the virus.
The authorities identified the Aljunied Crescent/Sims Drive area as the initial Zika cluster after more than 41 people working and living in the area tested positive for the virus.
But on Wednesday (Aug 31), the Ministry of Health (MOH) said the area around Bedok North Avenue 3, which is about five kilometres away from Aljunied Crescent/Sims Drive, could be the site of a new cluster.
As of Thursday, a total of 151 locally transmitted Zika infections were confirmed in Singapore, including three cases not linked to any existing cluster. On the same day, Prime Minister Lee Hsien Loong warned that Singapore "must assume Zika is elsewhere in (the country)" apart from Aljunied and Bedok, where the majority of cases so far have been.
Dr Asok Kurup, an infectious diseases specialist at Mount Elizabeth Hospital, said the spread was not surprising as Singapore is a small country and people can get around easily. He added that the virus could have already spread to other parts of Singapore.
“We are all very physically mobile within the country. It’s not unusual to find areas, clusters outside of there. Someone who works there can live in another part of Singapore; someone who has no symptoms can easily be a prey of the Aedes mosquito and it can spread to individuals in other neighbourhoods,” said Dr Kurup.
The Zika virus is transmitted by the Aedes mosquito. Symptoms of Zika include fever and rash as well as red eyes or joint pain. The disease can also cause microcephaly - a congenital condition in which the head size is much smaller than usual for a baby of the same age, race and sex.
DIFFICULT TO ERADICATE ZIKA: HEALTH EXPERTS
If Zika continues to spread across Singapore, Dr Leong Hoe Nam, an infectious diseases specialist at Mount Elizabeth Novena Hospital, is concerned that it may be difficult to eradicate the virus.
“The bigger the area to cover, the more difficult it will be to eradicate the virus. It means having to put more people on the ground, searching premises by premises and some of them are locked. Given this scenario, we will have more premises that are unchecked and more places where breeding can occur. When there are more areas for breeding, we are going to see a larger population of mosquitoes. This will translate to more cases of Zika and more cases of dengue,” said Dr Leong. "It will become inevitable that Zika may just take up permanent residence in Singapore."
His views were echoed by Dr Kurup, who said that apart from focusing on intensive vector control measures, other strategies including vaccines and the use of technology will be needed in the battle against Zika.
“We will not be able to eradicate Zika,” said Dr Kurup. “We have a huge challenge in that. We have no vaccine; we have no drugs; we have no targeted measures apart from what we have already done for dengue.”
Dr Wong Sin Yew, an infectious diseases specialist at Gleneagles Hospital, said the difficulty in eradicating the virus is that the majority of Zika cases are asymptomatic or mildly symptomatic.
“Eighty per cent of the people who are infected don't have any symptoms so it's possible for somebody who did not seek medical attention to be a source for mosquitoes to bite and infect others and these so-called 'silent carriers' could form a source of infection elsewhere and then develop other clusters,” said Dr Wong.
MOSQUITO CONTROL OPERATIONS UNDERWAY IN AFFECTED CLUSTERS
Vector control operations are underway in the Sims Drive/Aljunied Crescent cluster and Bedok North Avenue 3. This has been extended to Punggol Way and Joo Seng, where two isolated cases have been found.
NEA has inspected about 5,500 premises in the Sims Drive/Aljunied Crescent cluster which covers Aljunied Crescent, Sims Drive, Paya Lebar Way and Kallang Way. The cluster has about 7,000 premises.
More than 300 personnel were deployed each day between Aug 27 and Aug 30 to carry out vector control operations and outreach efforts.
On Thursday, MOH and the National Environment Agency (NEA) said that 49 breeding habitats - comprising 26 in homes and 23 in common areas or other premises - have been detected and destroyed in the Aljunied Crescent/Sims Drive cluster.
Indoor spraying, misting and oiling were conducted, and daily misting of common areas is ongoing. Two rounds of thermal fogging have been completed and another round will be conducted this week.
Even as authorities conduct vector control activities in the affected clusters, the community should also play an active role to prevent mosquito breeding, said Dr Wong.
“Every citizen should make sure that their house does not breed mosquitoes. If we reduce mosquito breeding throughout Singapore, we have a huge impact of reducing not just Zika but also dengue,” he said.
“The control efforts have been instituted and they are adequate. I would say that (in) two to three weeks ... we will be able to tell whether the number of cases will drop,” Dr Wong ventured.