Spatial and temporal patterns of Ross River virus in South East Queensland, Australia: identification of hot spots at the rural-urban interface

Abstract

Background: Ross River virus (RRV) is responsible for the most common vector-borne disease of humans reported in Australia. The virus circulates in enzootic cycles between multiple species of mosquitoes, wildlife reservoir hosts and humans. Despite regular outbreaks, ongoing morbidity and substantial economic costs, the underlying determinants of epidemics remain unclear. Public health concern about RRV has recently increased due to rising incidence rates in Australian urban centres, along with increased circulation in Pacific Island countries. Australia experienced its largest recorded outbreak of 9,544 cases in 2015, with the majority reported from South East Queensland (SEQ). We aimed to provide a detailed analysis of disease trends and explore potential links between disease patterns and transmission pathways of RRV. Methods: We assessed the spatial and temporal distribution of notified RRV cases, and associated epidemiological features in SEQ, from 2001-2016. This included fine-scale analysis of disease patterns across the suburbs of the capital city of Brisbane, and those of 8 adjacent Local Government Areas, and host spot analyses to identify locations with significantly high incidence. Results: The mean annual incidence rate for the region was 41/100,000 with a consistent seasonal peak in cases between February and May. The highest RRV incidence was in adults aged from 30-64 years (mean incidence rate: 59/100,000), and females had higher incidence rates than males (mean incidence rates: 44/100,000 and 34/100,000, respectively). Spatial patterns of disease were heterogeneous between years, and there was a wide distribution of disease across both urban and rural areas of SEQ. Overall, the highest incidence rates were reported from predominantly rural suburbs to the north of Brisbane City, with significant hot spots located in peri-urban suburbs where residential, agricultural and conserved natural land use types intersect. Conclusions: Although RRV is endemic across all of SEQ, transmission is most concentrated in areas where urban and peri-urban environments intersect. The drivers of RRV transmission across rural-urban landscapes should be prioritised for further investigation, including identification of specific vectors and hosts that mediate human spillover.

Ross River Virus Infection: A Cross-Disciplinary Review with a Veterinary Perspective

“…Queensland has consistently been the state with the highest number of reported cases, and the Northern Territory has had the highest notification rate (per 100,000) every year since 2010 (up to 2015) [ 4 , 39 , 40 , 41 , 42 ]. RRV transmission occurs throughout the year in the tropical coastal northeastern Australia with peaks associated with heavy monsoonal rainfalls [ 43 , 44 , 45 ]; in the subtropical Southeast Queensland area, RRV peaks between February and May [ 46 ]; the temperate area has epidemic activity, peaking between March and April, with sporadic cases reported at other times [ 44 , 47 ]. This is further evidenced by higher seroprevalence rates in blood donors in Northern Australia (22% in Townville; 15% in Darwin) as compared to Southern Australia (4% in Sydney; 0.84% in Melbourne) [ 48 ].…”

“…Landscape structure, such as river systems, floodwaters, wetlands, and marshlands, have been described in outbreak situations [ 49 ]. This is potentially further complicated by agricultural practices [ 46 ].…”

Seasonal Assessment of Quality of Groundwater from Private Owned Wells in Unguja Island Zanzibar

“…Studies have shown that outbreaks of water-related diseases have both spatial and temporal variations. The outbreaks are more common in peri-urban areas with unplanned housing compared to urban and villages [14]. Similarly, waterborne disease outbreaks are very high in wet seasons and rarely occur in dry seasons.…”