What is the fine-grained topic of the following text: We therefore used samples (collected during February-March 2012) from a study investigating hepatitis E virus (HEV) in pigs from Cameroon (7) to analyze the occurrence of porcine HoV in pigs in Africa and to determine the respective genotype. Only return the topic.
Analysis of porcine HoV occurrence and genotyping in Cameroon pigs.