Multiple outbreaks of acute hemorrhagic conjunctivitis due to a variant of coxsackievirus A24: Guangdong, China, 2007

Acute hemorrhagic conjunctivitis (AHC) is usually caused by enterovirus 70, coxsackievirus A24(CA24v) and adenoviruses. Several outbreaks of AHC caused by a CA24v have occurred since it was imported into China in 1971. Multiple outbreaks of AHC reappeared in 10 cities of Guangdong during June to November in 2007. The epidemic began in the June, and spread extensively, with a peak in the September. A total of 31,659 cases were reported to center for disease control and prevention of Guangdong, it was estimated that the number of actual AHC was >200 thousands. Forty conjunctival swab specimens were collected from the cases diagnosed clinically with AHC. (RT)-PCR testing on these conjunctival specimens revealed the presence of an enterovirus, and this was confirmed by 16 isolates. We demonstrated the most likely etiological agent for the multiple outbreaks was a variant of coxsackievirus A24 by molecular typing using a partial VP1 sequence. Sequence comparison and phylogenetic analyses of the VP1 and 3Cpro gene regions were performed by Neighbor-joining method, the strains from different outbreaks and different geographical areas within Guangdong had no sequence divergence in 2007. The representative isolates from mainland of China including Hangzhou, Ningbo, Beijing, Yunnan, Liaoning, and Henan were analyzed in this study. Phylogenetic analysis revealed theses isolates were located in different clusters, a close phylogenetic and chronological relationship with Singaporean, South Korean and Thailand isolates had been observed. This confirms CA24v circulated in China's mainland has not evolved independently, but co-evolved with the isolates of Southeast Asia.