Association between climate variables and pulmonary tuberculosis incidence in Brunei Darussalam, 2001 - 2018

Abstract Seasonality of tuberculosis is a long known but less understood phenomenon, particularly in equatorial countries. This study investigated the association between climate variables and pulmonary tuberculosis (PTB) incidence in Brunei Darussalam. Weekly data on PTB case counts and climate variables from January 2001 to December 2018 were analysed using the distributed lag non-linear model (DLNM) framework. After adjusting for long term trend and seasonality, multivariable analysis showed inverse association between PTB incidence and minimum temperature (relative risk [RR] significant up till the first 12 lagged weeks), total rainfall (RR significant after lag 12), and total sunshine hours (RR significant after lag 12). We also found a positive association between PTB incidence and mean relative humidity (RR significant up till the first 8 lagged weeks). No significant results were observed for average wind speed. Our findings reveal evidence of seasonal variation in PTB incidence in Brunei, but with varying degrees of magnitude, direction and timing. Though explainable by environmental and social factors, further studies on the relative contribution of recent (through primary human-to-human transmission) and remote (through reactivation of latent TB) TB infection in equatorial settings is warranted.