Impact of seasonal variations in malaria transmission on the surveillance of gene deletions.

Ten countries have reported gene deletions since the first observation of -deleted parasites in 2012. In a previous study (Watson et al., 2017), we characterised the drivers selecting for deletions and mapped the regions in Africa with the greatest selection pressure. In February 2018, the World Health Organization issued guidance on investigating suspected false-negative rapid diagnostic tests (RDTs) due to deletions. However, no guidance is provided regarding the timing of investigations. Failure to consider seasonal variation could cause premature decisions to switch to alternative RDTs. In response, we have extended our methods and predict that the prevalence of false-negative RDTs due to deletions is highest when sampling from younger individuals during the beginning of the rainy season. We conclude by producing a map of the regions impacted by seasonal fluctuations in deletions and a database identifying optimum sampling intervals to support malaria control programmes.