Lydeamore MJ1,2, Campbell PT2,3, Cuningham W3, Andrews RM4,5, Kearns T4, Clucas D6, Gundjirryirr Dhurrkay R4, Carapetis J7, Tong SYC 5,8, McCaw JM1, McVernon J2,3,9. Calculation of the age of the first infection for skin sores and scabies in five remote communities in northern Australia. Epidemiol Infect. 146(9): 1194–1201 (2018) https://doi.org/10.1017/S0950268818001061
Prevalence of skin sores and scabies in remote Australian Aboriginal communities remains unacceptably high, with Group A Streptococcus (GAS) the dominant pathogen. We aim to better understand the drivers of GAS transmission using mathematical models. To estimate the force of infection, we quantified the age of first skin sores and scabies infection by pooling historical data from three studies conducted across five remote Aboriginal communities for children born between 2001 and 2005. We estimated the age of the first infection using the Kaplan–Meier estimator; parametric exponential mixture model; and Cox proportional hazards. For skin sores, the mean age of the first infection was approximately 10 months and the median was 7 months, with some heterogeneity in median observed by the community. For scabies, the mean age of the first infection was approximately 9 months and the median was 8 months, with significant heterogeneity by the community and an enhanced risk for children born between October and December. The young age of the first infection with skin sores and scabies reflects the high disease burden in these communities.