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Association between the proportion of Plasmodium falciparum and Plasmodium vivax infections detected by passive surveillance and the magnitude of the asymptomatic reservoir in the community: a pooled analysis of paired health facility and community data

Gillian Stresman 1, * Nuno Sepúlveda 1, 2 Kimberly Fornace 1 Lynn Grignard 1 Julia Mwesigwa 3 Jane Achan 3 John Miller 4 Daniel Bridges 4 Thomas Eisele 5 Jacklin Mosha 6 Pauline Lorenzo 7 Maria Macalinao 7 Fe Esperanza Espino 7 Fitsum Tadesse 8 Jennifer Stevenson 9 Antonio Quispe 10 André Siqueira 11, 12, 13 Marcus Lacerda 11, 14 Shunmay Yeung 1 Siv Sovannaroth 15 Emilie Pothin 16, 17 Joanna Gallay 16 Karen E Hamre 18 Alyssa Young 19 Jean Frantz Lemoine 20 Michelle A Chang 18 Koukeo Phommasone 21 Mayfong Mayxay 21, 22, 23 Jordi Landier 24 Daniel M Parker 25 Lorenz Von Seidlein 26, 22 François Nosten 22, 27 Gilles Delmas 22, 27 Arjen Dondorp 26, 22 Ewan Cameron 28, 29 Katherine Battle 30 Teun Bousema 8 Peter Gething 28, 29 Umberto Alessandro 1, 3 Chris Drakeley 1
* Corresponding author
Abstract : Background Passively collected malaria case data are the foundation for public health decision making. However, because of population-level immunity, infections might not always be sufficiently symptomatic to prompt individuals to seek care. Understanding the proportion of all Plasmodium spp infections expected to be detected by the health system becomes particularly paramount in elimination settings. The aim of this study was to determine the association between the proportion of infections detected and transmission intensity for Plasmodium falciparum and Plasmodium vivax in several global endemic settings. Methods The proportion of infections detected in routine malaria data, P(Detect), was derived from paired household cross-sectional survey and routinely collected malaria data within health facilities. P(Detect) was estimated using a Bayesian model in 431 clusters spanning the Americas, Africa, and Asia. The association between P(Detect) and malaria prevalence was assessed using log-linear regression models. Changes in P(Detect) over time were evaluated using data from 13 timepoints over 2 years from The Gambia. Findings The median estimated P(Detect) across all clusters was 12⋅5% (IQR 5⋅3-25⋅0) for P falciparum and 10⋅1% (5⋅0-18⋅3) for P vivax and decreased as the estimated log-PCR community prevalence increased (adjusted odds ratio [OR] for P falciparum 0⋅63, 95% CI 0⋅57-0⋅69; adjusted OR for P vivax 0⋅52, 0⋅47-0⋅57). Factors associated with increasing P(Detect) included smaller catchment population size, high transmission season, improved care-seeking behaviour by infected individuals, and recent increases (within the previous year) in transmission intensity. Interpretation The proportion of all infections detected within health systems increases once transmission intensity is sufficiently low. The likely explanation for P falciparum is that reduced exposure to infection leads to lower levels of protective immunity in the population, increasing the likelihood that infected individuals will become symptomatic and seek care. These factors might also be true for P vivax but a better understanding of the transmission biology is needed to attribute likely reasons for the observed trend. In low transmission and pre-elimination settings, enhancing access to care and improvements in care-seeking behaviour of infected individuals will lead to an increased proportion of infections detected in the community and might contribute to accelerating the interruption of transmission. Funding Wellcome Trust.
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https://www.hal.inserm.fr/inserm-03079015
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Submitted on : Thursday, December 17, 2020 - 8:53:08 AM
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Gillian Stresman, Nuno Sepúlveda, Kimberly Fornace, Lynn Grignard, Julia Mwesigwa, et al.. Association between the proportion of Plasmodium falciparum and Plasmodium vivax infections detected by passive surveillance and the magnitude of the asymptomatic reservoir in the community: a pooled analysis of paired health facility and community data. The Lancet Infectious Diseases, New York, NY : Elsevier Science ; The Lancet Pub. Group, 2001-, 2020, 20 (8), pp.953-963. ⟨10.1016/S1473-3099(20)30059-1⟩. ⟨inserm-03079015⟩

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