Inferring transmission trees to guide targeting of interventions against visceral leishmaniasis and post-kala-azar dermal leishmaniasis

Lloyd A. C. Chapman; Simon E. F. Spencer; Timothy M. Pollington; Chris P. Jewell; Dinesh Mondal; Jorge Alvar; T. Deirdre Hollingsworth; Mary M. Cameron; Caryn Bern; Graham F. Medley

Based on the relative infectiousness of VL and the di erent 151 types of PKDL from the xenodiagnostic data, in the absence 152 of any other sources of transmission, the estimated probability 153 of being infected and developing VL if living in the same 154 household as a single symptomatic individual for 1 month 155 following their onset was 0.018 (95% CI: 0.013, 0.024) for VL 156 and ranged from 0.009 to 0.023 (95% CIs: (0.007,0.013)-(0.018, 157 0.031)) for macular/papular PKDL to nodular PKDL. Living 158 in the same household as a single asymptomatic individual, 159 the monthly risk of VL was only 0.00037 (95% CI: 0.00027, 160 0.00049), if asymptomatic individuals are 2% as infectious as 161 VL cases. 162 The risk of infection if living in the same household as an 163 infectious individual was estimated to be more than 10 times 164 higher than that if living directly outside the household of an 165 infectious individual (hazard ratio = 12.0), with a 95% CI 166 well above 1 (8.3, 16.7). The estimated spatial kernel (Fig. 167 S16 ) around each infectious individual shows a relatively rapid 168 decay in risk with distance outside their household, the risk of 169 infection halving over a distance of 84m (95% CI: 71, 99m).