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Ong J.B.S.,Tan Tock Seng Hospital | Chen M.I.-C.,Tan Tock Seng Hospital | Chen M.I.-C.,National University of Singapore | Cook A.R.,National University of Singapore | And 7 more authors.
PLoS ONE | Year: 2010

Background: Reporting of influenza-like illness (ILI) from general practice/family doctor (GPFD) clinics is an accurate indicator of real-time epidemic activity and requires little effort to set up, making it suitable for developing countries currently experiencing the influenza A (H1N1 -2009) pandemic or preparing for subsequent epidemic waves. Methodology/Principal Findings: We established a network of GPFDs in Singapore. Participating GPFDs submitted returns via facsimile or e-mail on their work days using a simple, standard data collection format, capturing: gender; year of birth; "ethnicity" residential status; body temperature (°C); and treatment (antiviral or not); for all cases with a clinical diagnosis of an acute respiratory illness (ARI). The operational definition of ILI in this study was an ARI with fever of 37.8°C or more. The data were processed daily by the study co-ordinator and fed into a stochastic model of disease dynamics, which was refitted daily using particle filtering, with data and forecasts uploaded to a website which could be publicly accessed. Twenty-three GPFD clinics agreed to participate. Data collection started on 2009-06-26 and lasted for the duration of the epidemic. The epidemic appeared to have peaked around 2009-08-03 and the ILI rates had returned to baseline levels by the time of writing. Conclusions/Significance: This real-time surveillance system is able to show the progress of an epidemic and indicates when the peak is reached. The resulting information can be used to form forecasts, including how soon the epidemic wave will end and when a second wave will appear if at all. © 2010 Ong et al. Source

Seah S.G.-K.,National Diagnostics | Lim E.A.-S.,National Diagnostics | Kok-Yong S.,National Diagnostics | Liaw J.C.-W.,National Diagnostics | And 5 more authors.
Journal of Clinical Virology | Year: 2010

Background: Military personnel are highly susceptible to febrile respiratory illnesses (FRI), likely due to crowding, stress and other risk factors present in the military environment. Objective: Our objective was to investigate the viral etiological agents responsible for FRI among military recruits training in a tropical climate in Singapore. Study design: From March 2006 through April 2007, a total of 1354 oropharyngeal (throat) swabs were collected from military recruits who reported sick with an oral temperature of ≥38 °C and a cough and/or sore throat. Real-time polymerase chain reaction (PCR) was used to assay for the presence of influenza A and B viruses and adenoviruses (H-AdV), and conventional PCR used for the remaining respiratory viruses in all specimens. Results: Influenza A virus was the dominant infection with a laboratory-confirmed incidence of 24% (326/1354) and a predominance of the H3N2 subtype. The temporal pattern for influenza A virus infections coincided with the nation-wide pattern in the civilian community. Detection rates of 12% (159/1354) and 2.7% (5/1354) were obtained for influenza B virus and other respiratory viruses, respectively. Conclusions: The laboratory findings identified influenza A virus as the primary causative viral agent for FRI in the Singapore military, in strong contrast to findings from temperate countries and countries where recruits are often vaccinated for influenza. Our results suggest that influenza vaccination should be considered as a requirement to reduce the incidence of influenza infections. This is the first report describing respiratory infections in a tropical military setting, in a developed country in Asia. © 2010 Elsevier B.V. Source

Carrasco L.R.,National University of Singapore | Lee L.K.,Communicable Disease Center | Lee V.J.,National University of Singapore | Lee V.J.,Biodefence Center | And 10 more authors.
PLoS Neglected Tropical Diseases | Year: 2011

Background: Dengue illness causes 50-100 million infections worldwide and threatens 2.5 billion people in the tropical and subtropical regions. Little is known about the disease burden and economic impact of dengue in higher resourced countries or the cost-effectiveness of potential dengue vaccines in such settings. Methods and Findings: We estimate the direct and indirect costs of dengue from hospitalized and ambulatory cases in Singapore. We consider inter alia the impacts of dengue on the economy using the human-capital and the friction cost methods. Disease burden was estimated using disability-adjusted life years (DALYs) and the cost-effectiveness of a potential vaccine program was evaluated. The average economic impact of dengue illness in Singapore from 2000 to 2009 in constant 2010 US$ ranged between $0.85 billion and $1.15 billion, of which control costs constitute 42%-59%. Using empirically derived disability weights, we estimated an annual average disease burden of 9-14 DALYs per 100 000 habitants, making it comparable to diseases such as hepatitis B or syphilis. The proportion of symptomatic dengue cases detected by the national surveillance system was estimated to be low, and to decrease with age. Under population projections by the United Nations, the price per dose threshold for which vaccines stop being more cost-effective than the current vector control program ranged from $50 for mass vaccination requiring 3 doses and only conferring 10 years of immunity to $300 for vaccination requiring 2 doses and conferring lifetime immunity. The thresholds for these vaccine programs to not be cost-effective for Singapore were $100 and $500 per dose respectively. Conclusions: Dengue illness presents a serious economic and disease burden in Singapore. Dengue vaccines are expected to be cost-effective if reasonably low prices are adopted and will help to reduce the economic and disease burden of dengue in Singapore substantially. © 2011 Carrasco et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Yap J.,Biodefence Center | Lee V.J.,Biodefence Center | Lee V.J.,National University of Singapore | Lee V.J.,Australian National University | And 4 more authors.
BMC Public Health | Year: 2010

Background. Effective influenza pandemic management requires understanding of the factors influencing behavioral changes. We aim to determine the differences in knowledge, attitudes and practices in various different cohorts and explore the pertinent factors that influenced behavior in tropical Singapore. Methods. We performed a cross-sectional knowledge, attitudes and practices survey in the Singapore military from mid-August to early-October 2009, among 3054 personnel in four exposure groups - laboratory-confirmed H1N1-2009 cases, close contacts of cases, healthcare workers, and general personnel. Results. 1063 (34.8%) participants responded. The mean age was 21.4 (SE 0.2) years old. Close contacts had the highest knowledge score (71.7%, p = 0.004) while cases had the highest practice scores (58.8%, p < 0.001). There was a strong correlation between knowledge and practice scores (r = 0.27, p < 0.01) and knowledge and attitudes scores (r = 0.21, p < 0.01). The significant predictors of higher practice scores were higher knowledge scores (p < 0.001), Malay ethnicity (p < 0.001), exposure group (p < 0.05) and lower education level (p < 0.05). The significant predictors for higher attitudes scores were Malay ethnicity (p = 0.014) and higher knowledge scores (p < 0.001). The significant predictor for higher knowledge score was being a contact (p = 0.007). Conclusion. Knowledge is a significant influence on attitudes and practices in a pandemic, and personal experience influences practice behaviors. Efforts should be targeted at educating the general population to improve practices in the current pandemic, as well as for future epidemics. © 2010 Yap et al; licensee BioMed Central Ltd. Source

Carrasco L.R.,National University of Singapore | Jit M.,Public Health England | Chen M.I.,National University of Singapore | Chen M.I.,Communicable Disease Center | And 4 more authors.
Emerging Themes in Epidemiology | Year: 2013

Background: The volume of influenza pandemic modelling studies has increased dramatically in the last decade. Many models incorporate now sophisticated parameterization and validation techniques, economic analyses and the behaviour of individuals. Methods. We reviewed trends in these aspects in models for influenza pandemic preparedness that aimed to generate policy insights for epidemic management and were published from 2000 to September 2011, i.e. before and after the 2009 pandemic. Results: We find that many influenza pandemics models rely on parameters from previous modelling studies, models are rarely validated using observed data and are seldom applied to low-income countries. Mechanisms for international data sharing would be necessary to facilitate a wider adoption of model validation. The variety of modelling decisions makes it difficult to compare and evaluate models systematically. Conclusions: We propose a model Characteristics, Construction, Parameterization and Validation aspects protocol (CCPV protocol) to contribute to the systematisation of the reporting of models with an emphasis on the incorporation of economic aspects and host behaviour. Model reporting, as already exists in many other fields of modelling, would increase confidence in model results, and transparency in their assessment and comparison. © 2013 Carrasco et al.; licensee BioMed Central Ltd. Source

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