Retrospective genome-wide comparisons of Salmonella enterica serovar Enteritidis from suspected outbreaks in Singapore.

The number of salmonellosis cases in Singapore has increased over the years. Salmonella enterica serovar Enteritidis has always been the most predominant serovar in the last five years. The National Public Health Laboratory assisted outbreak investigations by performing multilocus variable number tandem repeat analysis (MLVA) on isolates that were collected at the time of the investigations. Isolates were defined as belonging to a particular cluster if they had identical MLVA patterns. Whilst MLVA has been instrumental in outbreak investigations, it may not be useful when outbreaks are caused by an endemic MLVA type. In this study, we analysed 67 isolates from 12 suspected outbreaks with known epidemiological links to explore the use of next-generation sequencing (NGS) for defining outbreaks. We found that NGS can confidently group isolates into their respective outbreaks. The isolates from each suspected outbreak were closely related and differed by a maximum of 3 single nucleotide polymorphisms (SNPs). They were also clearly separated from isolates that belonged to different suspected outbreaks. This study provides an important insight and further evidence on the value of NGS for routine surveillance and outbreak detection of S. Enteritidis.

Epidemiologic update on the dengue situation in the Western Pacific Region, 2011.

Dengue is an emerging vectorborne infectious disease that is a major public health concern in the Asia and the Pacific. Official dengue surveillance data for 2011 provided by ministries of health were summarized as part of routine activities of the World Health Organization Regional Office for the Western Pacific. Based on officially reported surveillance data, dengue continued to show sustained activity in the Western Pacific Region. In 2011, Member States reported a total of 244,855 cases of which 839 died for a case fatality rate of 0.34%. More than 1000 cases were reported each from Cambodia, the Federated States of Micronesia, the Lao People's Democratic Republic, Malaysia, the Philippines, the Marshall Islands, Singapore and Viet Nam. Cambodia, the Federated States of Micronesia and the Marshall Islands reported higher activity relative to 2010. There continues to be great variability among the dengue-endemic countries and areas in the Region in the number of cases and serotype distribution. The continued high notification rate and complex dengue epidemiology in the Region highlight the need for information-sharing on a routine and timely basis.

Outbreak of novel influenza A (H1N1-2009) linked to a dance club.

INTRODUCTION: This paper describes the epidemiology and control of a community outbreak of novel influenza A (H1N1-2009) originating from a dance club in Singapore between June and July 2009. MATERIALS AND METHODS: Cases of novel influenza A (H1N1-2009) were confirmed using in-house probe-based real-time polymerase chain reaction (PCR). Contact tracing teams from the Singapore Ministry of Health obtained epidemiological information from all cases via telephone. RESULTS: A total of 48 cases were identified in this outbreak, of which 36 (75%) cases were patrons and dance club staff, and 12 (25%) cases were household members and social contacts. Mathematical modelling showed that this outbreak had a reproductive number of 1.9 to 2.1, which was similar to values calculated from outbreaks in naïve populations in other countries. CONCLUSION: This transmission risk occurred within an enclosed space with patrons engaged in intimate social activities, suggesting that dance clubs are places conducive for the spread of the virus.

Epidemiological characteristics of imported and locally-acquired malaria in Singapore.

INTRODUCTION: The objective of the study was to determine the trend of malaria, the epidemiological characteristics, the frequency of local transmission and the preventive and control measures taken. MATERIALS AND METHODS: We analysed the epidemiological records of all reported malaria cases maintained by the Communicable Diseases Division, Ministry of Health, from 1983 to 2007 and the Anopheles vector surveillance data collected by the National Environment Agency during the same period. RESULTS: The annual incidence of reported malaria ranged from 2.9 to 11.1 per 100,000 population, with a sharp decline observed after 1997. There were 38 deaths, 92.1% due to falciparum malaria and 7.9% due to vivax malaria. Of the reported cases, 91.4% to 98.3% were imported, with about 90% originating from Southeast Asia and the Indian subcontinent. Among the various population groups with imported malaria, the proportion of cases involving work permit/employment pass holders had increased, while that of local residents had decreased. Between 74.8% and 95.1% of the local residents with imported malaria did not take personal chemoprophylaxis when they travelled overseas. Despite the extremely low Anopheles vector population, a total of 29 local outbreaks involving 196 cases occurred. Most of the larger outbreaks could be traced to foreign workers with imported relapsing vivax malaria and who did not seek medical treatment early. One of the outbreaks of 3 cases in 2007 was caused by Plasmodium knowlesi, a newly recognised simian malaria which was probably acquired in a forested area where long-tail macaques had been sighted. CONCLUSIONS: Singapore remains both vulnerable and receptive to the reintroduction of malaria and a high level of vigilance should be maintained indefinitely to prevent the re-establishment of endemicity. Medical practitioners should highlight the risk of malaria to travellers visiting endemic areas and also consider the possibility of simian malaria in a patient who has no recent travel history and presenting with daily fever spikes and with malaria parasite morphologically similar to that of P. malariae.

Entomologic and virologic investigation of Chikungunya, Singapore.

Local transmission of chikungunya, a debilitating mosquito-borne viral disease, was first reported in Singapore in January 2008. After 3 months of absence, locally acquired Chikungunya cases resurfaced in May 2008, causing an outbreak that resulted in a total of 231 cases by September 2008. The circulating viruses were related to East, Central, and South African genotypes that emerged in the Indian Ocean region in 2005. The first local outbreak was due to a wild-type virus (alanine at codon 226 of the envelope 1 gene) and occurred in an area where Aedes aegypti mosquitoes were the primary vector. Strains isolated during subsequent outbreaks showed alanine to valine substitution (A226V) and largely spread in areas predominated by Ae. albopictus mosquitoes. These findings led to a revision of the current vector control strategy in Singapore. This report highlights the use of entomologic and virologic data to assist in the control of chikungunya in disease-endemic areas.