We then tested the hypothesis that dry season parasitemias were maintained low and subclinical due to decreased parasite replication capacity during this period . We cultured P. falciparum for 36 - 48 h in vitro directly after blood draw from rapid diagnostic test positive ( RDT + ) samples of asymptomatic individuals at three time points of the dry season ( January , March and May ) and from samples of children presenting with their first clinical malaria episode of the ensuing transmission season ( MAL ) . By flow cytometry , we measured the increase in parasitemia and parasite development at 0 , 16 However , the number of hours in culture needed to increase parasitemia was shorter in the dry season samples than in samples from malaria - causing parasites in the transmission season ( Fig . 5a ) . In accordance with an earlier increase in parasitemia in vitro during the dry season , we could frequently identify on Giemsa smears mature schizonts after 16 and 24 h of culture and young ring stages after 30 or 36 h in the dry season samples , whereas mature schizonts of malaria - causing parasite samples were mostly observed after 36 h in culture , and young ring stages were largely found after 48 h in vitro ( Fig . 5b ) . When we calculated the number of hours in culture at which the highest increase of parasitemia could be detected for each sample , we observed that it decreased from the beginning to the end of the dry season - January , 26   in the wet season ( Fig . 5d ) . Finding later developmental parasite stages at earlier times in this short - term in vitro experiment during the dry season could indicate a faster than 48 - h intraerythrocytic replicative cycle , or , alternatively , that dry season parasites circulate longer without adhering to the host vascular endothelium and were more developed than circulating parasites in clinical malaria cases at the time of the blood draw . To test the latter , we used the RNA - seq data described in Fig . 4 to estimate , with a likelihood - based statistical method previously described 28 , the age in hours post - invasion ( hpi ) of circulating parasites from subclinical children at the end of the dry season ( May ) and from clinical cases during the wet season ( MAL ) . We determined that parasites circulating in the dry season had a transcriptional signature of ~17 hpi , 95%CI ( 14.05 , 20.8 ) , whereas parasites circulating in malaria cases during the wet season had a transcription profile similar to parasites with ~7 hpi , 95 % CI ( 6.5 , 7.7 ) ( Fig . 5e ) . Accordingly , imaging the thick blood films made in the field at the time of the blood draw , we confirmed that the more developed trophozoite stages of P. falciparum were present on subclinical samples collected at the end dry season , whereas clinical malaria samples in the transmission season presented much smaller ring stages of P. falciparum ( Fig . 5f , g ) . All together , these data show that , at the end of the dry season , P. falciparum can be found circulating at later stages of the ~48 - h asexual cycle than what is seen during clinical malaria cases in the wet season .