452 Marius Gilbert et al. Fig. 1. Distribution of outbreaks, duck density, and HPAI H5N1 presence probability predicted by two risk models. a: Distribution of HPAI H5N1 virus outbreaks in Bangladesh, India, Myanmar, Thailand, Cambodia, Laos, and Vietnam (data for Thailand and Vietnam differentiate records from the second wave [in blue] from (>20 ducks/km2), and for regions where it was considered low or absent ( 20 ducks/km2). Two spatial epidemio- logical models were developed: one with combined H5N1 outbreak data from India, Bangladesh, Myanmar, Thailand, Cambodia, Laos, and Vietnam (South and Southeast Asia Model), and a second one using only data from India, Bangladesh, and Myanmar (South Asia Model). The South and Southeast Asia Model showed a very good capacity to discriminate HPAI H5N1 presence and absence over all seven countries (Table 1), and highly sig- niﬁcant risk factors included chicken density, duck density, human population density, and high versus low duck farming areas (Table 2). Four distinct subregions at risk of HPAI H5N1 were identiﬁed (Fig. 1c): Bangladesh and northeastern India, southern Myanmar, the central plain of Thailand, and the Mekong and Red River Deltas in Viet- records that took place afterward [in red]). b: Distribution of domestic duck density (heads/km2). c, d: Predicted probability of HPAI H5N1 virus presence by the South and Southeast Asia Model, and the South Asia Model, respectively. nam. The South Asia Model compares well to the com- bined model except that the continuous variable of duck density was no longer identiﬁed as a signiﬁcant risk factor. However, duck versus no-duck farming remained a highly signiﬁcant factor (Table 2), and details of model parame- ters (see Table S2) showed that chicken density in South Asia was a signiﬁcant risk factor only when duck farming was present at relatively high densities (>20 ducks /km2; signiﬁcant interaction term). The distribution of HPAI H5N1 predicted by the second model is concentrated in Bangladesh and northeastern India, the Mekong and Red River Deltas in Vietnam, and to a lesser extent in the central plain of Thailand and in Myanmar. The wild waterfowl marked with satellite transmitters along the Central Asia ﬂyway began their spring migration in March, and converged at the Qinghai Lake region in