During the last decade, and despite the documented rapid microscopy determined parasite clearance of artemether-lumefantrine in Bagamoyo District, interest has developed in understanding the observation of high residual polymerase chain reaction (PCR) determined positivity rate on day 3 after supervised artemether-lumefantrine treatment in the magnitude of almost 30% in previous assessments from 2015. Using deep sequencing approaches studies have recently detected PCR determined delayed parasite clearance curves in P. falciparum sub-populations in Bagamoyo District. The clearance times by PCR of these sub-populations were similar to artemisinin resistant parasites in Myanmar as assessed by microscopy, but the former did, importantly, not harbor any of the described mutations in Kelch13 propeller associated with artemisinin resistance. However, these Tanzanian parasite sub-populations need to be further studied and characterized since they may provide important clues to the understanding of artemisinin survival strategies among the East African P. falciparum parasite population.