Why has malaria only now started to develop resistance against artemisinin, considering the compound has been in use for about two millennia in its herbal form in China?
In recent years, parasite resistance to artemisinins has been detected in four countries of the Greater Mekong subregion: Cambodia, Myanmar, Thailand and Viet Nam.
However, the compound artemisinin has been used in its herbal form since at least around 400AD, when it was documented in the well known medical text 肘后方.
What are some reasons that malaria has only begun developing resistance now?
I would imagine that modern artemisinin would be more effective in completely eliminating malaria, as compared to use in its traditional herbal form. This means semi-resistant strains would more likely be killed before they are able to spread or develop resistance any further.