How Rainfall Matters? The Association between Rainfall and Rotavirus and Norovirus infection in Hong Kong

Abstract

Introduction The association between temperature and infectious diseases has been well documented. However, the influence of change in the precipitation pattern is less known. This study aims to quantify the impact of precipitation on the hospitalizations due to norovirus and rotavirus infection in Hong Kong. Methods Daily counts of all Hong Kong public hospital admissions for norovirus and rotavirus infection from January 1st 2002 to December 31st 2011 were obtained. Generalized additive regression models were constructed for time-series analysis with hospitalizations as the outcome and meteorological variables, including rainfall, as predictors. Different lag effects of rainfall during the hot season and cool season were evaluated by distributed lag non-linear models. Results Less rainfall was associated with more admissions for rotavirus. Specifically, compared to 99th percentile of rainfall (128mm) in summer, no daily rainfall, about 34% of all days0, was found to be associated with a cumulative (0-13 days) 260% (95%CI 1.16-11.19) increase in the risk of rotavirus hospitalization. However, heavy precipitation was associated with more norovirus hospitalizations. The association was apparent at lags 0-3 in summer and 0-28 days in winter. Extreme rainfall (99th percentile) was associated with 1.18 (95%CI 1.01-1.39) times the risk of norovirus infection relative to no rainfall in summer. Norovirus hospitalizations were approximately linearly associated with precipitation in winter, with 10.17 (95%CI 3.07-33.64) times the cumulative risk of extreme rainfall (34mm) relative to no rainfall. Conclusions Rainfall has a strong short-term association with both norovirus and rotavirus hospitalizations in Hong Kong, which go in opposite directions. Climate change, which has been causing alterations of precipitation pattern worldwide, will also likely change norovirus and rotavirus infection patterns in subtropical Asian cities without further interventions.