Estimating malaria disease burden in the Asia-Pacific

Background: The Asia-Pacific aims to eliminate malaria by 2030. Many of the 22 endemic countries have earlier targets. To track progress towards elimination and predict timelines and funding required it is essential to have an accurate picture of the true burden of malaria over time. Estimating this is a major challenge with most countries having incomplete data on numbers of cases and wide variation between health system access and performance. Regular estimates are published by the World Health Organization (WHO), but these are not split by species, can have a wide range of uncertainty, change over time and are not available for every year. Methods: For the Asia Pacific Leaders Malaria Alliance, the burden of malaria for the 22 malaria-endemic countries in the Asia-Pacific from 2000 to 2015 was estimated by combining data submitted by countries to WHO with a systematic review to estimate the proportion of cases recorded. Due to a lack of suitable data, it was only possible to apply this method to 2013-2015. A simplified method was then derived to estimate the annual burden of falciparum and vivax malaria as inputs to a mathematical model to predict the cost of elimination, which is described elsewhere. Results: The total number of estimated cases was around double the number of confirmed cases reported in the Asia Pacific with a broad range of uncertainty around these estimates due primarily to sparsity of data with which to estimate proportions of cases reported. The ranges of estimated burdens were mostly like those published for countries by WHO, with some exceptions. Conclusions: The accuracy and precision of malaria burden estimates could be greatly improved by having more regular large surveys on access to healthcare in malaria-endemic areas and making subnational data on malaria incidence and reporting completeness publicly available.