National Influenza Surveillance in the Philippines from 2006 to 2012: seasonality and circulating strains.

BACKGROUND: The results of routine influenza surveillance in 13 regions in the Philippines from 2006 to 2012 are presented, describing the annual seasonal epidemics of confirmed influenza virus infection, seasonal and alert thresholds, epidemic curve, and circulating influenza strains. METHODS: Retrospective analysis of Philippine influenza surveillance data from 2006 to 2012 was conducted to determine seasonality with the use of weekly influenza positivity rates and calculating epidemic curves and seasonal and alert thresholds using the World Health Organization (WHO) global epidemiological surveillance standards for influenza. RESULTS: Increased weekly influenza positive rates were observed from June to November, coinciding with the rainy season and school opening. Two or more peaks of influenza activity were observed with different dominant influenza types associated with each peak. A-H1N1, A-H3N2, and two types of B viruses circulated during the influenza season in varying proportions every year. Increased influenza activity for 2012 occurred 8 weeks late in week 29, rather than the expected week of rise of cases in week 21 as depicted in the established average epidemic curve and seasonal threshold. The intensity was severe going above the alert threshold but of short duration. Southern Hemisphere vaccine strains matched circulating influenza virus for more surveillance years than Northern Hemisphere vaccine strains. CONCLUSIONS: Influenza seasonality in the Philippines is from June to November. The ideal time to administer Southern Hemisphere influenza vaccine should be from April to May. With two lineages of influenza B circulating annually, quadrivalent vaccine might have more impact on influenza control than trivalent vaccine. Establishment of thresholds and average epidemic curve provide a tool for policy-makers to assess the intensity or severity of the current influenza epidemic even early in its course, to help plan more precisely resources necessary to control the outbreak. Influenza surveillance activities should be continued in the Philippines and funding for such activities should already be incorporated into the Philippine health budget.

Reconstructing the phylodynamic history and geographic spread of the CRF01_AE-predominant HIV-1 epidemic in the Philippines from PR/RT sequences sampled from 2008 to 2018.

The Philippines has had a rapidly growing human immunodeficiency virus (HIV) epidemic with a shift in the prevalent subtype from B to CRF01_AE. However, the phylodynamic history of CRF01_AE in the Philippines has yet to be reconstructed. We conducted a descriptive retrospective study reconstructing the history of HIV-1 CRF01_AE transmissions in the Philippines through molecular epidemiology. Partial polymerase sequences (n = 1144) collected between 2008 and 2018 from three island groups were collated from the Research Institute for Tropical Medicine drug resistance genotyping database. Estimation of the time to the most recent common ancestor (tMRCA), effective reproductive number (Re), effective viral population size (Ne), relative migration rates, and geographic spread of CRF01_AE was performed with BEAST. Re and Ne were compared between CRF01_AE and B. Most CRF01_AE sequences formed a single clade with a tMRCA of June 1996 [95 per cent highest posterior density (HPD): December 1991, October 1999]. An increasing CRF01_AE Ne was observed from the tMRCA to 2013. The CRF01_AE Re reached peaks of 2.46 [95 per cent HPD: 1.76, 3.27] in 2007 and 2.52 [95 per cent HPD: 1.83, 3.34] in 2015. A decrease of CRF01_AE Re occurred in the intervening years of 2007 to 2011, reaching as low as 1.43 [95 per cent HPD: 1.06, 1.90] in 2011, followed by a rebound. The CRF01_AE epidemic most likely started in Luzon and then spread to the other island groups of the country. Both CRF01_AE and Subtype B exhibited similar patterns of Re fluctuation over time. These results characterize the subtype-specific phylodynamic history of the largest CRF01_AE cluster in the Philippines, which contextualizes and may inform past, present, and future public health measures toward controlling the HIV epidemic in the Philippines.

Enhanced Health Facility Surveys to Support Malaria Control and Elimination across Different Transmission Settings in the Philippines.

Following substantial progress in malaria control in the Philippines, new surveillance approaches are needed to identify and target residual malaria transmission. This study evaluated an enhanced surveillance approach using rolling cross-sectional surveys of all health facility attendees augmented with molecular diagnostics and geolocation. Facility surveys were carried out in three sites representing different transmission intensities: Morong, Bataan (pre-elimination), Abra de Ilog, Occidental Mindoro (stable medium risk), and Rizal, Palawan (high risk, control). Only one rapid diagnostic test (RDT)-positive infection and no PCR confirmed infections were found in Bataan and Occidental Mindoro, suggesting the absence of transmission. In Palawan, the inclusion of all health facility attendees, regardless of symptoms, and use of molecular diagnostics identified 313 infected individuals in addition to 300 cases identified by routine screening of febrile patients with the RDT or microscopy. Of these, the majority (313/613) were subpatent infections and only detected using molecular methods. Simultaneous collection of GPS coordinates on tablet-based applications allowed real-time mapping of malaria infections. Risk factor analysis showed higher risks in children and indigenous groups, with bed net use having a protective effect. Subpatent infections were more common in men and older age-groups. Overall, malaria risks were not associated with participants' classification, and some of the non-patient clinic attendees reported febrile illnesses (1.9%, 26/1,369), despite not seeking treatment, highlighting the widespread distribution of infection in communities. Together, these data illustrate the utility of health facility-based surveys to augment surveillance data to increase the probability of detecting infections in the wider community.

Underdetection of laboratory-confirmed influenza-associated hospital admissions among infants: a multicentre, prospective study.

BACKGROUND: Since influenza often presents non-specifically in infancy, we aimed to assess the extent to which existing respiratory surveillance platforms might underestimate the frequency of severe influenza disease among infants. METHODS: The Influenza and Respiratory Syncytial Virus in Infants (IRIS) study was a prospective observational study done at four hospitals in Albania, Jordan, Nicaragua, and the Philippines. We included acutely ill infants aged younger than 1 year admitted to hospital within 10 days or less of illness onset during two influenza seasons (2015-16 and 2016-17) in Albania, Jordan, and Nicaragua, and over a continuous 34 week period (2015-16) in the Philippines. We assessed the frequency of influenza virus infections by real-time RT-PCR (rRT-PCR) and serology. The main study outcome was seroconversion, defined as convalescent antibody titres more than or equal to four-fold higher than acute sera antibody titres, and convalescent antibody titres of 40 or higher. Seroconverison was confirmed by haemagglutination inhibition assay for influenza A viruses, and by hemagglutination inhibition assay and microneutralisation for influenza B viruses. FINDINGS: Between June 27, 2015, and April 21, 2017, 3634 acutely ill infants were enrolled, of whom 1943 were enrolled during influenza seasons and had complete acute-convalescent pairs and thus were included in the final analytical sample. Of the 1943 infants, 94 (5%) were influenza-positive by both rRT-PCR and serology, 58 (3%) were positive by rRT-PCR-only, and 102 (5%) were positive by serology only. Seroconversion to at least one of the influenza A or B viruses was observed among 196 (77%) of 254 influenza-positive infants. Of the 254 infants with influenza virus, 84 (33%) only had non-respiratory clinical discharge diagnoses (eg, sepsis, febrile seizures, dehydration, or other non-respiratory viral illness). A focus on respiratory diagnoses and rRT-PCR-confirmed influenza underdetects influenza-associated hospital admissions among infants by a factor of 2·6 (95% CI 2·0-3·6). Findings were unchanged when syndromic severe acute respiratory infection criteria were applied instead of clinical diagnosis. INTERPRETATION: If the true incidence of laboratory-confirmed influenza-associated hospital admissions among infants is at least twice that of previous estimates, this substantially increases the global burden of severe influenza and expands our estimates of the preventive value of maternal and infant influenza vaccination programmes. FUNDING: US Centers for Disease Control and Prevention.

Estimates of influenza and respiratory syncytial virus incidences with fraction modeling approach in Baguio City, the Philippines, 2012-2014.

BACKGROUND: Estimation of the incidences of influenza and respiratory syncytial virus (RSV) infection is important for disease control. Previous estimate in the city showed a substantial burden of influenza in both outpatients and inpatients while it did not account for individuals who do not seek medical attention nor RSV. PATIENTS/METHODS: A total of 17 674 influenza-like illness (ILI) and 13 242 severe acute respiratory illness (SARI) cases were recruited, and samples were collected from 6267 and 2962 of ILI and SARI cases, respectively. RT-PCR assays were performed to detect influenza and RSV in the samples. A health-seeking behavior survey was conducted from February 2014 to April 2014 to estimate the fraction of infected individuals who did not seek medical attention between rainy and dry season. RESULTS: Average influenza and RSV incidence rates in outpatients were 1.6 and 1.4 per 1000 individuals, respectively, and the highest incidence rate for both viruses was found in the of 6-23 month age group. Average influenza and RSV hospitalization incidence rates were 1.7 and 1.9 per 1000 individuals, respectively. Further, we estimated that the incidence rates of influenza and RSV in individuals who did not seek medical attention were threefold and 1.6-fold those in the medically attended population. CONCLUSIONS: Respiratory syncytial virus and influenza pose a substantial disease burden, particularly in hospitalized cases. The implementation of either a community-based approach or an enhanced surveillance system in combination with a community survey will allow a better understanding of the disease burdens of RSV and influenza in the Philippines.

The dire sexual health crisis among MSM in the Philippines: an exploding HIV epidemic in the absence of essential health services.

The rate of HIV is exploding in the men who have sex with men (MSM) population in the Philippines. There is a paucity of information with respect to sexual behaviour, condom use, psychological health, and the prevalence of other STIs in the MSM subpopulation. At present there are no existing private or public clinical services in the country that focus on health services of MSM. We discuss the current epidemic situation and the steps needed to further define the rapidly evolving epidemic among MSM.

Estimating influenza outpatients' and inpatients' incidences from 2009 to 2011 in a tropical urban setting in the Philippines.

OBJECTIVES: 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. DESIGN: 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. RESULTS AND CONCLUSIONS: 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.

Epidemiological characterization of influenza A(H1N1)pdm09 cases from 2009 to 2010 in Baguio City, the Philippines.

BACKGROUND: 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. OBJECTIVES: We aimed to investigate the epidemiological and clinical features of A(H1)pdm09 in pandemic and post-pandemic periods. METHODS: 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. RESULTS AND CONCLUSIONS: 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.