- Design
- Nationwide cross-sectional molecular surveys plus clinical follow-up
- Population
- 1949 P falciparum isolates across Zambia; 98 treated patients in Kaoma
- Primary outcome
- Pfkelch13 mutation prevalence and day-3 parasite positivity
- Effect
- A724E day-3 positivity 28% vs 0% wild type (p=0.0026); Kaoma prevalence 0% to 79%
Two nationwide cross-sectional surveys in Zambia in 2024 genotyped Plasmodium falciparum for Pfkelch13 mutations, alongside clinical follow-up in Kaoma in Western Province. Published in The Lancet Infectious Diseases on 7 October 2026.
A previously unreported mutation, A724E, was found in about half of isolates in Western and North-Western provinces and 12% nationally. In Kaoma, 28% of patients with mutant parasites were still parasitaemic on day 3 of artemisinin-based combination therapy, against none with wild-type parasites. Its prevalence there rose from 0% in 2018 to 79% in 2026. Laboratory susceptibility testing did not show reduced sensitivity, a discordance still to be explained.
Delayed clearance is the clinical signature of partial resistance. It does not yet mean treatment failure, because the partner drug still clears the infection, but it puts that partner drug under pressure.
India has its own history of artemisinin partial resistance in the north-east. Returning travellers from southern Africa with falciparum malaria need close follow-up.
- Check a blood film on day 3 in falciparum malaria acquired in Zambia or neighbouring countries
- Ask every febrile patient about recent travel to southern or eastern Africa
- Treat persistent parasitaemia on day 3 as a reason to review the case with an ID specialist
- Report suspected treatment failure to the national malaria programme
Why it matters
Partial resistance is now emerging in southern Africa, not only the east, which widens where travellers can acquire it.
Don't overread it
Delayed clearance is not treatment failure; artemisinin combinations still cured these infections.
The statistics, in plain English
The day-3 comparison (28% vs 0%) rests on small numbers, especially 23 wild-type patients, so the true difference is uncertain. The steady rise in prevalence over eight years is the more robust signal.
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