Malaria surveillance is a practice concerned with collection and analysis of data. This paper presents an ethnographical account of an international team of researchers producing data about malaria in the Zanzibar archipelago. We show that malaria is increasingly an electronic entity, inextricably interwoven with the practices of data workers using ICT tools. The use of mobile ICT tools enables new data production practices that include situated coordination mechanisms such that 1) more people can be surveyed, including individuals not suffering from malaria but possibly carrying the parasite, 2) greater geographical areas can be covered, and 3) more data can be validated and included in malaria statistics. As electronic data, malaria builds and mobilizes diverse human, organizational, and infrastructural worlds around it, who must now be dedicated to its production, management, and care. We discuss implications for design of digital data collection tools that support the work of teams surveying malaria, as well as implications for disease surveillance methods and practices.