Portia P Alday

The Research Institute for Tropical Medicine, Manila, Metro Manila, Philippines

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Publications (8)25.74 Total impact

  • PLoS ONE 05/2015; 10(5):e0125009. DOI:10.1371/journal.pone.0125009 · 3.53 Impact Factor
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    ABSTRACT: Although the public health significance of influenza in regions with a temperate climate has been widely recognized, information on influenza burden in tropical countries, including the Philippines, remains limited. We aimed to estimate influenza incidence rates for both outpatients and inpatients then characterized their demographic features. An enhanced surveillance was performed from January 2009 to December 2011 in an urbanized highland city. The influenza-like illness (ILI) surveillance involved all city health centers and an outpatient department of a tertiary government hospital. The severe acute respiratory infection (sARI) surveillance was also conducted with one government and four private hospitals since April 2009. Nasal and/or oropharyngeal swabs were collected and tested for influenza A, influenza B, and respiratory syncytial virus. We obtained 5915 specimens from 13 002 ILI cases and 2656 specimens from 10 726 sARI cases throughout the study period. We observed year-round influenza activity with two possible peaks each year. The overall influenza detection rate was 23% in the ILI surveillance and 9% in the sARI surveillance. The mean annual outpatient incidence rate of influenza was 5·4 per 1000 individuals [95% confidence interval (CI), 1·83-12·7], and the mean annual incidence of influenza-associated sARI was 1·0 per 1000 individuals (95% CI, 0·03-5·57). The highest incidence rates were observed among children aged <5 years, particularly those aged 6-23 months. Influenza posed a certain disease burden among inpatients and outpatients, particularly children aged <5 years, in an urbanized tropical city of the Philippines.
    Influenza and Other Respiratory Viruses 01/2014; DOI:10.1111/irv.12223 · 1.90 Impact Factor
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    ABSTRACT: Baguio City, Philippines experienced its first influenza A(H1N1)pdm09 [A(H1)pdm09] case in May 2009. In spite of numerous reports describing the epidemiological and clinical features of A(H1)pdm09 cases, there are no studies about A(H1)pdm09 epidemiology in the Philippines, where year-round influenza activity was observed. We aimed to investigate the epidemiological and clinical features of A(H1)pdm09 in pandemic and post-pandemic periods. Data were collected under enhanced surveillance of influenza-like illness (ILI) and severe acute respiratory infection (SARI) from January 2009 to December 2010. RT-PCR was used to detect A(H1)pdm09, following the protocol of the United States Centers for Disease Control and Prevention. The reproduction number was computed as a simple exponential growth rate. Differences in proportional and categorical data were examined using chi-square test or Fishers' exact test. The outbreak was observed from week 25 to 35 in 2009 and from week 24 to 37 in 2010. The highest proportion of cases was among children aged 5-14 years. The number of ILI outpatients was 2.3-fold higher in 2009 than in 2010, while the number of inpatients was 1.8-fold higher in 2009. No significant difference in gender was observed during the two periods. The clinical condition of all patients was generally mild and self-limiting, with only 2 mortalities among inpatients in 2009. The basic reproduction number was estimated as 1.16 in 2009 and 1.05 in 2010 in the assumption of mean generation time as 2.6 days. School children played a significant role in facilitating influenza transmission.
    PLoS ONE 11/2013; 8(11):e79916. DOI:10.1371/journal.pone.0079916 · 3.53 Impact Factor
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    ABSTRACT: In the year 2000, the Philippines' Department of Health adopted mass chemotherapy using praziquantel to eliminate schistosomiasis. Mass treatment was offered to an eligible population of 30 187 residents of 50 villages in Western Samar, the Philippines, in 2004 as part of an ongoing epidemiological study, Schistosomiasis Transmission and Ecology in the Philippines (STEP), aimed at measuring the effect of irrigation on infection with schistosomiasis. This paper describes the mass-treatment activities and factors associated with participation. Advocacy, information dissemination and social mobilization activities were conducted before mass chemotherapy. Village leaders were primarily responsible for community mobilization. Mass treatment was offered in village meeting halls and schools. Participation proportions were estimated based on the 2002-2003 census. Community involvement was measured using a participation index. A Bayesian hierarchical logistic regression model was fitted to estimate the association between sociodemographic factors and residents coming to the treatment site. A village-level average of 53.1% of residents (range: 21.1-85.3) came to the treatment site, leading to a mass-treatment coverage with an average of 48.3% (range: 15.8-80.7). At the individual level, participation proportions were higher among males, preschool and school-age children, non-STEP participants and among those who provided a stool sample. At the village-level, better community involvement was associated with increased participation whereas a larger census was associated with decreased participation. The conduct of mass treatment in the 50 villages resulted in far lower participation than expected. This raises concern for the ongoing mass-treatment initiatives now taking place in developing countries.
    Bulletin of the World Health Organisation 11/2008; 86(10):765-71. DOI:10.2471/BLT.07.047563 · 5.11 Impact Factor
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    ABSTRACT: The usefulness of rapid diagnostic tests (RDT) in malaria case management depends on the accuracy of the diagnoses they provide. Despite their apparent simplicity, previous studies indicate that RDT accuracy is highly user-dependent. As malaria RDTs will frequently be used in remote areas with little supervision or support, minimising mistakes is crucial. This paper describes the development of new instructions (job aids) to improve health worker performance, based on observations of common errors made by remote health workers and villagers in preparing and interpreting RDTs, in the Philippines and Laos. Initial preparation using the instructions provided by the manufacturer was poor, but improved significantly with the job aids (e.g. correct use both of the dipstick and cassette increased in the Philippines by 17%). However, mistakes in preparation remained commonplace, especially for dipstick RDTs, as did mistakes in interpretation of results. A short orientation on correct use and interpretation further improved accuracy, from 70% to 80%. The results indicate that apparently simple diagnostic tests can be poorly performed and interpreted, but provision of clear, simple instructions can reduce these errors. Preparation of appropriate instructions and training as well as monitoring of user behaviour are an essential part of rapid test implementation.
    Transactions of the Royal Society of Tropical Medicine and Hygiene 02/2007; 101(1):9-18. DOI:10.1016/j.trstmh.2006.03.011 · 1.93 Impact Factor
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    ABSTRACT: To estimate the association between the intensity of animal infection with Schistosoma japonicum and human infection in Western Samar province, the Philippines. We conducted an observational cross-sectional study of 1425 households in 50 villages. Stool samples were collected on each of 1-3 days from 5623 humans, 1275 cats, 1189 dogs, 1899 pigs, 663 rats and 873 water buffalo. Intensity of infection with S. japonicum was measured by the number of eggs per gram (EPG). Egg counts were done using the Kato-Katz method. We used a Bayesian hierarchical cumulative logit model, with adjustments for age, sex, occupation and measurement error. The adjusted proportions of humans lightly infected (classified as 1-100 EPG) was 17.7% (95% Bayesian credible interval = 15.3-20.2%); the proportion classified as at least moderately infected (>100 EPG) was 3.2% (2.2-4.6%). The crude parasitological results for animals indicated that 37 cats (2.9%), 228 dogs (19.2%), 39 pigs (2.1%), 199 rats (30.0%) and 28 water buffalo (3.2%) were infected. In univariate analyses the odds ratios corresponding to a unit increase in the mean number of EPG at the village-level in dogs was 1.05 (1.01-1.09), in cats 1.35 (1.02-1.78), in pigs 1.16 (0.24- 5.18) and in rats 1.00 (1.00-1.01). Mean EPG values in cats, dogs, pigs and rats were correlated with one another. This confounding made interpreting the odds ratios difficult, but the odds ratios for dogs and cats were more consistent. S. japonicum is endemic in areas of the Philippines despite implementation of control programmes. This may be due to the association of infections in dogs and cats with human infections. Infection control in dogs and cats is challenging, and there is a need to develop new methods to control transmission across all species.
    Bulletin of the World Health Organisation 07/2006; 84(6):446-52. DOI:10.2471/BLT.05.026427 · 5.11 Impact Factor
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    ABSTRACT: Schistosomiasis japonica is a chronic helminthic infection contracted through contact with water infested with Schistosoma japonicum. The infection is associated with severe disease and is an important public health concern in Philippines. To estimate the agreement in the frequency of water contact between bimonthly interviews, self-administered diaries and observations. A total of 286 individuals were followed over either a 4 or a 6 months period. Agreement between direct observation and both the bimonthly and diary methods were estimated. The agreement between the observation and the bimonthly interview was 71.8% when days without any water contacts were considered, but decreased to 23.3% when only days with at least some water contact were considered. The agreement between the observation and the diary was 78.7% when days without any water contacts were considered and 40.8% when only days with some water contacts were considered. Agreement about the degree of water contact is poor between the different measurement tools. This has important implications for future research, since a high degree of measurement error can severely bias any results from studies involving water contact.
    Tropical Medicine & International Health 07/2006; 11(6):834-42. DOI:10.1111/j.1365-3156.2006.01638.x · 2.30 Impact Factor
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    ABSTRACT: Few studies have described heterogeneity in Schistosoma japonicum infection intensity, and none were done in Philippines. The purpose of this report is to describe the village-to-village variation in the prevalence of two levels of infection intensity across 50 villages of Samar Province, the Philippines. This cross-sectional study was conducted in 25 rain-fed and 25 irrigated villages endemic for S. japonicum between August 2003 and November 2004. Villages were selected based on irrigation and farming criteria. A maximum of 35 eligible households were selected per village. Each participant was asked to provide stool samples on three consecutive days. All those who provided at least one stool sample were included in the analysis. A Bayesian three category outcome hierarchical cumulative logit regression model with adjustment for age, sex, occupation and measurement error of the Kato-Katz technique was used for analysis. A total of 1427 households and 6917 individuals agreed to participate in the study. A total of 5624 (81.3%) participants provided at least one stool sample. The prevalences of those lightly and at least moderately infected varied from 0% (95% Bayesian credible interval (BCI): 0%-3.1%) to 45.2% (95% BCI: 36.5%-53.9%) and 0% to 23.0% (95% BCI: 16.4%-31.2%) from village-to-village, respectively. Using the 0-7 year old group as a reference category, the highest odds ratio (OR) among males and females were that of being aged 17-40-year old (OR = 8.76; 95% BCI: 6.03-12.47) and 11-16-year old (OR = 8.59; 95% BCI: 4.74-14.28), respectively. People who did not work on a rice farm had a lower prevalence of infection than those working full time on a rice farm. The OR for irrigated villages compared to rain-fed villages was 1.41 (95% BCI: 0.50-3.21). We found very important village-to-village variation in prevalence of infection intensity. This variation is probably due to village-level variables other than that explained by a crude classification of villages into the irrigated and non-irrigated categories. We are planning to capture this spatial heterogeneity by updating our initial transmission dynamics model with the data reported here combined with 1-year post-treatment follow-up of study participants.
    BMC Public Health 02/2006; 6(1):61. DOI:10.1186/1471-2458-6-61 · 2.32 Impact Factor