Dynamics of asymptomatic infections and symptomatic malaria show different temporal profiles among infants living in a high transmission area of Ghana

Abstract Background Although infants are vulnerable to malaria, the characteristics of their patterns of infections are not well described. This study aimed to examine the longitudinal profiles of asymptomatic infections and symptomatic malaria in the first year of life. Methods A birth cohort in Kintampo, Ghana (N = 1855) was followed actively with monthly blood sampling and passively for any febrile illness between 2008 and 2011. Malaria parasites were detected by light microscopy and infants who were infected or uninfected were identified. Infections were classified as either symptomatic or asymptomatic using fever and temperature readings over twelve months of follow up. The longitudinal infection profiles in all infants were then compared. Results: Asymptomatic infections and symptomatic malaria were observed at all ages but were rare the first months of life and the proportion of symptomatic malaria increased after six months. Among 1264 infants having microscopy data for at least eight monthly visits, four patterns were observed: parasite negative at all visits (36%), always asymptomatic (7%), always symptomatic (35%) and alternating between asymptomatic infections and symptomatic malaria (22%). The cumulative incidence of infection was highest in the alternating group, and many different profiles (87 different combinations) of asymptomatic infections and symptomatic malaria were observed in this group . Parasite densities were significantly low for the always asymptomatic group and highest for always symptomatic group. Conclusion Infants in malaria endemic areas experience highly different infection profiles over the first year of life despite living in the same area. In-depth investigations of why some infants are parasite free and others have repeated symptomatic malaria or maintain asymptomatic infections or alternate between asymptomatic infections and symptomatic malaria can contribute to understanding malaria susceptibility during infancy.