Outbreaks of epidemic keratoconjunctivitis caused by human adenovirus type 8 in the Tibet Autonomous Region of China in 2016

Abstract

From April to November 2016, two outbreaks of epidemic keratoconjunctivitis (EKC) occurred successively at primary and middle schools in the Tibet Autonomous Region of China, and a total of 197 clinically diagnosed cases were reported. Real-time PCR analyses confirmed that human adenovirus (HAdV) infection was related to these outbreaks. Further studies involving sequence determination and phylogenetic analysis based on the penton base, hexon, and fiber genes indicated that human adenovirus type 8 (HAdV-8), belonging to species D, was responsible for the outbreaks. This is the first report of a HAdV-8 associated EKC outbreak in mainland of China, and the results of this study are expected to provide support for future research into HAdV-8 in China.

Fig 1. Preliminary type identification of samples collected from two EKC outbreaks in Tibet in 2016, based on the partial hexon gene.

Phylogenetic trees were generated using the maximum-likelihood method with 1000 replicates. Samples collected in Namling County are indicated by red dots and samples from Gongbujiangda County are indicated by blue triangles. Strains shown in red were used for further analysis. Sequences of the 30 prototype HAdV strains representing the seven HAdV species (A-G) are available in the GenBank database.

Fig 2. Phylogenetic analysis of sequences of HAdV-8 strains from the outbreaks in Tibet compared to HAdV-8 strains from other countries and 32 HAdV species D viruses based on (a) the entire penton gene; (b) the entire hexon gene; (c) the entire fiber gene.

Phylogenetic trees were generated using the maximum-likelihood method with 1000 replicates. HAdV-8 strains isolated in Tibet are highlighted in red, and HAdV-8 strains from other countries are indicated by blue triangles.