Search

Few studies have formally examined the relationship between meteorological factors and the incidence of child pneumonia in the tropics, despite the fact that most child pneumonia deaths occur there. We examined the association between four meteorological exposures (rainy days, sunshine, relative humidity, temperature) and the incidence of clinical pneumonia in young children in the Philippines using three time-series methods: correlation of seasonal patterns, distributed lag regression, and case-crossover. Lack of sunshine was most strongly associated with pneumonia in both lagged regression [overall relative risk over the following 60 days for a 1-h increase in sunshine per day was 0·67 (95% confidence interval (CI) 0·51–0·87)] and case-crossover analysis [odds ratio for a 1-h increase in mean daily sunshine 8–14 days earlier was 0·95 (95% CI 0·91–1·00)]. This association is well known in temperate settings but has not been noted previously in the tropics. Further research to assess causality is needed.

Well balanced ecosystems have an essential role in disease regulation, and consequently their correct functioning is increasingly recognised as imperative for maintaining human health. Disruptions to ecosystems have been found to increase the risk of several diseases, including Hantavirus, Lyme disease, Ross River virus, malaria and Ciguatera fish poisoning. Leptospirosis is a globally important emerging zoonosis, caused by spirochaete bacteria, borne by many mammalian hosts, and also transmitted environmentally. We propose that leptospirosis incidence in humans is also linked to ecosystem disruption, and that reduced biodiversity (the diversity of species within an ecological community) may be associated with increased leptospirosis incidence. To investigate this hypothesis, the relationship between biodiversity levels of island nations and their annual leptospirosis incidence rates (adjusted for GDP per capita) was examined by linear correlation and regression. Supportive, statistically significant negative associations were obtained between leptospirosis incidence and (a) total number of species (r2=0.69, p<0.001) and (b) number of mammal species (r2=0.80, p<0.001) in univariate analysis. In multivariable analysis only the number of mammal species remained significantly associated (r2=0.81, p=0.007). An association between biodiversity and reduced leptospirosis risk, if supported by further research, would emphasise the importance of managing the emergence of leptospirosis (and other infectious diseases) at a broader, ecosystem level.