Figure 6.

Early detection of pre-patent parasitemia in six volunteers experimentally infected with Plasmodium falciparum. Sporozoites kinetics of parasite load determined by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) during challenge of six human volunteers with P. falciparum 3D7 sporozoites. For qRT-PCR, venous blood was collected twice daily starting on Day 5. The first qRT-PCR positive sample in each participant is denoted with a black arrow listing the day post-challenge. Thick blood smears were positive starting on Day 9 (participant 5), 11 (participants 1–4) and 14 (participant 6), as denoted with circles. Chloroquine treatment was initiated on the first detection of a positive thick smear. The limit of quantification (20 parasites/mL) is indicated with a horizontal line. Samples from subjects 1 and 2 that were positive by melting curve analysis but were below the limit of quantification were plotted at the “+” level on the parasitemia axis.