Historically, the serotype prevalent in Hong Kong has been and continues to be serotype O. Regarding the last cases, the Pirbright laboratory reported the topotype as being Cathay. However, the results that returned at the end of March from Pirbright indicated that the topotype had changed from Cathay to Southeast Asia topotype on their phylogenetic chart, which is considered as a variation in the strain and appropriate to be reported to the OIE.
Note by the OIE Animal Health Information Department: This is a summary for three outbreaks. Details for the other two outbreaks will be provided in the follow-up report.