Nipah Virus Strain Variation

摘要

To the Editor: AbuBakar et al.described strain variation in Nipahvirus during the 1998–1999 outbreakin Malaysia (1). They found an isolatefrom pigs in Perak, as well as from aflying fox, that differed markedlyfrom pig and human isolates from themain epidemic in southern Malaysia.AbuBakar et al. proposed that thisfinding indicates 2 separate spilloverevents from bats to pigs occurred, thefirst in Perak in 1998 and the secondin southern Malaysia in 1999.However, investigations at the time ofthe outbreak showed that many pigswere moved from Perak onto southernfarms in early 1999. We suggest thatsuccessive spillovers of the pig popu-lation in the north can also explain theobserved strain differences betweennorthern and southern isolates