One consequence of lower health care resources is that the threshold for detection (i.e., the number of cases that need to occur before a case is detected, tested and confirmed by medical authorities) is likely higher in lower-income countries that cannot afford to invest as much in public health and healthcare infrastructure. Similar socioeconomic factors have been shown to play an important role in determining spatiotemporal patterns of diseases such as tuberculosis, schistosomiasis, West Nile virus, and HIV/AIDS [12, 13, 25, 26] .