Only 24 hours ago Singapore's MOH announced their 1st Locally Acquired Zika Case, and today we learn they have now identified at least 41 locally acquired cases, 7 of which are still symptomatic and have been hospitalized to prevent forward transmission.
Given Singapore's population density (#3rd in the world with nearly 8,000 per sq. km), it's location just 1 degree north of the equator, and an ample supply of Aedes mosquitoes, the Zika virus appears to has a lot going in its favor.
Working in vector control's favor - June, July, and August are the driest months of the year in Singapore - and the true `rainy season' doesn't begin until November.
Also, although it was planned months ago to help with the suppression of Dengue, yesterday Singapore's National Environment Agency (NEA) announced plans to Conduct Wolbachia-Aedes Small-Scale Field Study At Three Selected Sites From October 2016.
You may recall we looked at the potential uses for Wolbachia infected mosquitoes in the fight against Zika last May in Cell Host & Microbe: Wolbachia Blocks Zika Virus In Brazilian Aedes Aegypti Mosquitoes.
Here is the full MOH announcement on 40 additional locally acquired Zika cases, including their expectation that more will be detected.
Localised Community Spread Of Zika Virus Infection With More Cases Confirmed
The Ministry of Health (MOH) has confirmed 41 cases of locally transmitted Zika virus infection in Singapore. Of these cases, 36 were identified through active testing of potentially infected persons.
Aljunied Crescent/ Sims Drive Cluster
2. All the cases are residents or workers in the Aljunied Crescent/ Sims Drive area. They are not known to have travelled to Zika-affected areas recently, and are thus likely to have been infected in Singapore. This confirms that local transmission of Zika virus infection has taken place. At this point, the community transmission appears to be localised within the Aljunied Crescent/ Sims Drive cluster.
3. 34 have fully recovered. The other 7, who are still symptomatic and potentially infectious, are recovering at Tan Tock Seng Hospital.
4. The profile of the 41 cases are as follows:
A 47-year-old female Malaysian had developed fever, rash and conjunctivitis from 25 August. She was referred to the Communicable Diseases Centre (CDC) at Tan Tock Seng Hospital, where she was tested positive for Zika on 27 August. She has since been hospitalised for observation at the CDC.
A Singaporean father and his son who reside at Block 62 Sims Drive. The former is a 65 year-old retiree, while his son is a 21 year-old full time National Serviceman who is doing his National Service at Khatib Camp. They developed symptoms of fever and rash from 23 August and 21 August respectively and were warded at CDC on 27 August.
A 30 year-old male Singaporean who works at a construction site at 60 Sims Drive and lives at Sembawang Drive. He developed fever and rash since 22 August and was warded at CDC on 27 August.
A 44-year-old unemployed male Singaporean who lives at Block 54 Sims Drive. He developed symptoms on 23 August and is currently warded at CDC.
36 foreign workers were tested positive, of which 7 are warded at the CDC. They were among the 118 persons working at the construction site at 60 Sims Drive who were tested. The other 29 who tested positive have fully recovered.
Other Areas of Concern
5. Given that the Zika virus is spread by the Aedes mosquito vector, MOH cannot rule out further community transmission in Singapore, since some of those tested positive also live or work in other parts of Singapore. At this point, these other areas of concern include Khatib Camp, Sembawang Drive and places where the construction workers live (Kranji Road, Joo Chiat Place, Senoko South Road, Toh Guan Road East and Lor 101 Changi).
Ongoing Screening and Testing
6. MOH will continue to screen the close contacts of confirmed cases. MOH is also carrying out Zika testing on others living and working in the Aljunied Crescent/ Sims Drive area and other areas of concern who have symptoms of fever and rash. In particular, MOH has worked with the contractors at a construction site at Sims Drive to screen the workers there who were recently reported by a general practitioner (GP) to have symptoms of fever, rash and conjunctivitis. We have verified with Khatib Camp that there were no symptomatic cases to date.
7. MOH has also alerted all GPs, polyclinics and hospitals to be extra vigilant and to immediately report patients with symptoms associated with Zika virus infection to MOH.
8. We expect to identify more positive cases. Given that the majority of Zika cases are asymptomatic or mildly symptomatic, and mosquitoes in the affected areas may already have been infected, isolation of positive cases may have limited effect to managing the spread. We should focus our efforts on vector control.
9. Since receiving notification from MOH on 27 August, NEA has intensified vector control operations to control the Aedes mosquito population in the vicinity of Aljunied Crescent/ Sims Drive. NEA has deployed more than 200 officers to inspect the area and conduct outreach to residents and other stakeholders in the vicinity. NEA’s intensified vector control operations include:
Inspecting all premises, ground and congregation areas
Conducting mandatory treatment such as ultra-low volume (ULV) misting/spraying of premises and thermal fogging of outdoor areas to kill adult mosquitoes
Increasing frequency of drain flushing and oiling to prevent breeding
Public education outreach and distribution of insect repellents
10. On 27 August, NEA accessed more than 1,800 premises out of an estimated 6,000 premises to check for mosquito breeding, and also conducted ground checks in the vicinity. 19 breeding habitats - comprising 13 in homes and 6 in common areas, were detected and destroyed
11. On 27 August, NEA also followed up on an earlier inspection on 24 August at the construction site at Sims Drive to re-inspect the site and conduct misting and thermal fogging. A Stop Work Order was issued to the construction site on 27 August, as the housekeeping of the construction site was found to be unsatisfactory with potential breeding habitats favourable to mosquito breeding. The construction site is required to rectify these conditions and step up preventive measures to prevent recurrence of mosquito breeding.
12. The on-site workers quarters at the construction site and two other dormitories at Senoko South and Kranji were also inspected on 27 August. One breeding was detected and destroyed at the dormitory at Kranji. NEA is conducting vector control operations at the remaining dormitories and the vicinity of Sembawang Drive today.
13. NEA officers and grassroots volunteers also conducted outreach in 14 blocks of flats in the vicinity of Aljunied Crescent and Sims Drive, to distribute Zika information leaflets and insect repellents on 27 August. We completed outreach to the remaining blocks in the vicinity on 28 August. NEA will similarly be conducting outreach in the Sembawang Drive residential area.
14. As the majority of people infected with the virus do not show symptoms, it is likely that some transmission may already have taken place before these cases of Zika were confirmed. Hence, even as NEA conducts operations to contain the transmission of the Zika virus, residents are urged to cooperate fully with NEA and allow its officers to inspect their premises for mosquito breeding and to spray insecticide to kill any mosquitoes. NEA may need to gain entry into inaccessible premises by force after serving of requisite Notices, to ensure any breeding habitats are destroyed quickly.
15. To minimise the risk of further spread of Zika in Singapore, it is critical that all of us as a community take immediate steps to prevent mosquito breeding in our homes by doing the 5-step Mozzie Wipeout and protect ourselves from mosquito bites by applying insect repellent regularly.
16. We advise those living or working in the affected area of Aljunied Crescent/ Sims Drive and the other areas of concern, especially pregnant women, to monitor their health. They should seek medical attention if they are unwell, especially with symptoms of fever and rash. They should also inform their doctors of the location of their residence and workplace.
17. Zika is generally a mild disease and many people infected with the Zika virus do not even develop symptoms. Like dengue, it is transmitted by the bite of an infected Aedes mosquito.
18. Zika virus infection can however cause microcephaly in the unborn foetuses of pregnant mkwomen. Pregnant women should adopt strict mosquitoes precaution if travelling to an affected area. Individuals working, studying or living in an affected area who are sexual partners of pregnant women should adopt safe sexual practices (e.g. consistent and correct use of condoms during sex) or consider abstinence throughout the women’s pregnancy.
19. MOH will provide updates on any further developments and our latest public health risk assessments. Singaporeans should refer to MOH’s webpage on Zika (www.moh.gov.sg/zika) for the latest health advisory.
 Of those tested, 78 were negative. 4 results are pending.
Last updated on 28 Aug 2016