The influence of air quality and meteorological variations on influenza A and B virus infections in a paediatric population in Singapore.

INTRODUCTION: Influenza is an important cause of paediatric illness across the globe. However, information about the relationships between air pollution, meteorological variability and paediatric influenza A and B infections in tropical settings is limited. METHODS: We analysed all daily reports of influenza A and B infections in children <5 years old obtained from the largest specialist women and children's hospital in Singapore. In separate negative binomial regression models, we assessed the dependence of paediatric influenza A and B infections on air quality and meteorological variability, using multivariable fractional polynomial modelling and adjusting for time-varying confounders. RESULTS: Approximately 80% of 7329 laboratory-confirmed reports were caused by influenza A. We observed positive associations between sulphur dioxide (SO2) exposure and the subsequent risk of infection with both influenza types. We observed evidence of a harvesting effect of SO2 on Influenza A but not Influenza B. Ambient temperature was associated with a decline in influenza A reports (Relative Risk at lag 5 [RRlag5]: 0.949, 95% CI: 0.916-0.983). Rainfall was positively associated with a subsequent increase in influenza A reports (RRlag3: 1.044, 95% CI: 1.017-1.071). Nitrogen dioxide (NO2) concentration was positively associated with influenza B reports (RRlag5: 1.015, 95% CI: 1.005-1.025). There was a non-linear association between CO and influenza B reports. Absolute humidity increased the ensuing risk of influenza B (RRlag5: 4.799, 95% CI: 2.277-10.118). Influenza A and B infections displayed dissimilar but predictable within-year seasonal patterns. CONCLUSIONS: We observed different independent associations between air quality and meteorological variability with paediatric influenza A and B infections. Anticipated seasonal infection peaks and variations in air quality and meteorological parameters can inform the timing of community measures aimed at reducing influenza infection risk.

Climate variability and seasonal patterns of paediatric parainfluenza infections in the tropics: An ecological study in Singapore.

OBJECTIVES: Evidence of the relationship between climate variability, air pollution and human parainfluenza virus (HPIV) infections has been inconsistent. We assessed this in a paediatric population from a highly urbanized tropical city-state. METHODS: We analysed all reports of HPIV infections in children <5 years old obtained from a major specialist women and children's hospital in Singapore. Assuming a negative binomial distribution and using multivariable fractional polynomial modelling, we examined the relations between climate variability, air quality and the risk of HPIV infections, adjusting for time-varying confounders. RESULTS: We identified 6393 laboratory-confirmed HPIV infections from 2009 to 2019. Every 1 °C decline in temperature was associated with a 5.8% increase (RR: 0.943, 95% Confidence Interval [95% CI]: 0.903-0.984) in HPIV infection risk 6 days later. Every 10% decrease in relative humidity was associated with a 15.8% cumulative increase in HPIV risk over the next 6 days (cumulative RR: 0.842, 95% CI: 0.771-0.919). Rainfall was positively associated with HPIV risk 2 days later (RR: 1.021, 95% CI: 1.000-1.043). A within-year seasonal rise of HPIV was driven by HPIV-3 and HPIV-1 and preceded by a seasonal decline in temperature. Gender was an effect modifier of the climate-HPIV relationship. Air quality was not associated with HPIV risk. CONCLUSIONS: This study demonstrates a close association between HPIV infection risk and tropical climate variability. The climate dependence and seasonal predictability of HPIV can inform the timing of community campaigns aimed at reducing infection risk and the development of hospital resources and climate adaption plans.

The burden of acute conjunctivitis attributable to ambient particulate matter pollution in Singapore and its exacerbation during South-East Asian haze episodes.

INTRODUCTION: Urban air quality in South-East Asia is influenced by local and transboundary sources of air pollutants. Research studies have well characterized the short-term effects of air pollution on cardiovascular and respiratory health but less so on ocular health. We investigated the relationship between air pollution and acute conjunctivitis in Singapore, a tropical city-state located in South-East Asia. METHODS: Assuming a negative-binomial distribution, we examined the short-term associations between all-cause acute conjunctivitis reports from 2009 to 2018 and contemporaneous ambient air pollutant concentrations using a time-series analysis. In separate pollutant models for PM2.5 and PM10, we fitted fractional polynomials to investigate the linearity between air pollutant exposures and conjunctivitis, adjusting for long-term trend, seasonality, climate variability, public holidays, immediate and lagged exposure effects, and autocorrelation. RESULTS: There were 261,959 acute conjunctivitis reports over the study period. Every 10 µg/m3 increase in PM2.5 was associated with a 3.8% (Incidence Rate Ratio (IRR): 1.038, 95% Confidence Interval (CI): 1.029-1.046, p < 0.001) cumulative increase in risk of conjunctivitis over the present and subsequent week. Every 10 µg/m3 increase in PM10 was associated with a 2.9% (Incidence Rate Ratio (IRR): 1.029, 95% Confidence Interval (CI): 1.022-1.036, p < 0.001) cumulative increase in risk of conjunctivitis over the present and subsequent week. Acute conjunctivitis reports exhibited an inverse dependence on ambient air temperature and relative humidity variability. Approximately 3% of all acute conjunctivitis reports were attributable to PM2.5. Particulate matter attributed acute conjunctivitis was disproportionately higher during transboundary haze episodes. CONCLUSION: Our study strengthens the evidence linking particulate matter exposure to an increased risk of conjunctival disease, with a disproportionately higher disease burden during South-East Asia transboundary haze episodes. Our findings underscore the importance of reducing the health impact of indigenous and transboundary sources of ambient particulate matter pollution.