The seasonality of infections in tropical Far North Queensland, Australia: A 21-year retrospective evaluation of the seasonal patterns of six endemic pathogens

Abstract

An understanding of the seasonality of infections informs public health strategies and assists clinicians in their management of patients with undifferentiated illness. The seasonality of infections is driven by a variety of environmental and human factors; however, the role of individual climatic factors has garnered much attention. This study utilises Poisson regression models to assess the seasonality of six important infections in tropical Australia and their association with climatic factors and severe weather events over a 21-year period. Melioidosis and leptospirosis showed marked wet season predominance, while more cases of rickettsial disease and cryptococcosis were seen in cooler, drier months. Staphylococcus aureus infections were not seasonal, while influenza demonstrated inter-seasonality. The climate did not significantly change during the 21 years of the study period, but the incidence of melioidosis and rickettsial disease increased considerably, highlighting the primacy of other factors—including societal inequality, and the impact of urban expansion—in the incidence of these infections. While anthropogenic climate change poses a threat to the region—and may influence the burden of these infections in the future—this study highlights the fact that, even for seasonal diseases, other factors presently have a greater effect on disease incidence. Public health strategies must also target these broader drivers of infection if they are to be effective.

Melioidosis and Burkholderia pseudomallei: progress in epidemiology, diagnosis, treatment and vaccination

“…The importance of melioidosis as a disease of socioeconomic disadvantage was established in analysis of the Cairns cohort, with socioeconomic disadvantage having a greater independent association with in-hospital death than age, indigenous status, bacteraemia and the classical risk factors for melioidosis, such as diabetes [47 ▪ ]. A 21-year analysis of seasonal and weather data confirmed the marked wet season predominance of melioidosis (and leptospirosis) [48]. Further south in Townsville, Queensland, melioidosis cases showed similar demographics and clinical presentations to Cairns and Darwin, Northern Territory [49].…”

Melioidosis in northern Australia

“…8,9 However, while anthropogenic climate change is anticipated to increase the future incidence of many seasonal infectious diseases, environmental disruption resulting from urban expansion appears to be having a greater impact on the incidence of melioidosis in Australia presently. 10,11 The predominant mode of exposure is thought to be percutaneous, although inhalation and ingestion are also documented. 12 Very few of these exposures lead to clinical symptoms; however, patients with specific comorbidities -particularly diabetes mellitus, chronic lung disease, chronic kidney disease, immunosuppression, malignancy, and hazardous alcohol consumption -are more likely to develop disease.…”

Clinical Manifestations and Genomic Evaluation of Melioidosis Outbreak among Children after Sporting Event, Australia

“…During the dry season, the organism is found at soil depths of > 30 cm, but during the wet season, monsoonal rains cause the rising water table to bring bacteria to the surface where they proliferate ( 9 ), increasing the risk for human exposure to the organism. That bacterial cycle also explains the strong seasonality of the disease ( 10 – 12 ).…”