Analysis of Severe and Relapse Risks of Imported Malaria in Five Provinces of China.

Although China has achieved malaria elimination certification, the risk of malaria transmission reintroduction due to imported malaria remains. We analyzed data on imported malaria cases collected from January 1, 2014 to December 31, 2021, using multivariable logistic regression analysis to identify the factors associated with severe and relapsing malaria. The odds of severe malaria were around 4-fold greater for patients who were initially diagnosed with a nonmalarial illness than for patients initially diagnosed with malaria. The risk of relapse from Plasmodium vivax or Plasmodium ovale varied depending on the regions of Africa where patients resided. Patients residing in western and southern Africa (compared with Central Africa) had a lower relative risk of relapse. In addition, treatment with primaquine provided protection against malaria relapse. Improving the timeliness of treatment of malaria patients could help reduce the severity of illness, and use of primaquine can mitigate the risk of relapse after treatment.