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Background: Acute respiratory infection (ARI) is of great concern in public health. It remains unclear whether viral infections can affect the host's susceptibility to subsequent ARIs.Methods: A prospective cohort study on ARIs of children below 5 years old was conducted in the Philippines from 2014 to 2016. The respiratory symptoms were recorded daily, and nasopharyngeal swabs were collected at both household and health facilities. The specimens were tested for respiratory viruses. We then determined whether viral etiology was associated with the severity of the present ARI and whether previous viral infections was associated with subsequent ARIs.Results: A total of 3851 children and 16337 ARI episodes were enrolled and recorded, respectively. Samples were collected from 24% of all ARI episodes; collection rate at the healthcare facilities was 95%. Enterovirus D68, rhinovirus species C, and respiratory syncytial virus were significantly associated with severe ARIs. The risk for subsequent ARIs was significantly enhanced after infections with adenovirus, influenza A virus, parainfluenza virus type 4, and rhinovirus species C.Conclusions: This study revealed that viral etiology plays a significant role in the severity of the present ARI and that viral infection affects the host's susceptibility to subsequent ARIs. [ABSTRACT FROM AUTHOR]

Introduction: The seasonality of influenza and respiratory syncytial virus (RSV) is well known, and many analyses have been conducted in temperate countries; however, this is still not well understood in tropical countries. Previous studies suggest that climate factors are involved in the seasonality of these viruses. However, the extent of the effect of each climate variable is yet to be defined. Materials and Methods: We investigated the pattern of seasonality and the effect of climate variables on influenza and RSV at three sites of different latitudes: the Eastern Visayas region and Baguio City in the Philippines, and Okinawa Prefecture in Japan. Wavelet analysis and the dynamic linear regression model were applied. Climate variables used in the analysis included mean temperature, relative and specific humidity, precipitation, and number of rainy days. The Akaike Information Criterion estimated in each model was used to test the improvement of fit in comparison with the baseline model. Results: At all three study sites, annual seasonal peaks were observed in influenza A and RSV; peaks were unclear for influenza B. Ranges of climate variables at the two Philippine sites were narrower and mean variables were significantly different among the three sites. Whereas all climate variables except the number of rainy days improved model fit to the local trend model, their contributions were modest. Mean temperature and specific humidity were positively associated with influenza and RSV at the Philippine sites and negatively associated with influenza A in Okinawa. Precipitation also improved model fit for influenza and RSV at both Philippine sites, except for the influenza A model in the Eastern Visayas. Conclusions: Annual seasonal peaks were observed for influenza A and RSV but were less clear for influenza B at all three study sites. Including additional data from subsequent more years would help to ascertain these findings. Annual amplitude and variation in climate variables are more important than their absolute values for determining their effect on the seasonality of influenza and RSV. [ABSTRACT FROM AUTHOR]

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 (s ARI) 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 s ARI 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 s ARI 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 s ARI 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. [ABSTRACT FROM AUTHOR]

The local and global transmission dynamics of influenza B virus is not completely understood mainly because of limited epidemiological and sequence data for influenza B virus. Here we report epidemiological and molecular characteristics of influenza B viruses from 2010 to 2013 in Leyte Island, Philippines. Phylogenetic analyses showed global dissemination of the virus among both neighboring and distant areas. The analyses also suggest that southeast Asia is not a distributor of influenza B virus and can introduce the virus from other areas. Furthermore, we found evidence on the local persistence of the virus over years in the Philippines. Taken together, both local persistence and global dissemination play a significant role in the circulation of influenza B virus. [ABSTRACT FROM AUTHOR]