Porcine epidemic diarrhea virus
It was first discovered in Europe , but has become increasingly problematic in Asian countries , such as Korea , China , Japan , the Philippines , and Thailand . 
<triplet> Korea <subj> Asia <obj> continent <triplet> China <subj> Asia <obj> continent <triplet> Japan <subj> Asia <obj> continent <triplet> Thailand <subj> Asia <obj> continent