Molecular epidemiological study of enterovirus D68 in hospitalised children in Hong Kong in 2014-2015 and their complete coding sequences.

Human enterovirus D68 (EV-D68) was first isolated in 1962 and has aroused public concern recently because of a nationwide outbreak among children in 2014-2015 in the USA. The symptoms include fever, runny nose, sneezing, cough and muscle pains. It might be associated with severe respiratory illness in individuals with pre-existing respiratory conditions and its potential association with acute flaccid myelitis is under investigation. In Asia, EV-D68 cases have been reported in several countries.We aimed to understand the EV-D68 prevalence and their genetic diversity in Hong Kong children.A total of 10 695 nasopharyngeal aspirate (NPA) samples from hospitalised patients aged <18 years were collected from September 2014 to December 2015 in two regional hospitals. NPAs tested positive for enterovirus/rhinovirus (EV/RV) were selected for genotyping. For those identified as EV-D68, their complete coding sequences (CDSs) were obtained by Sanger sequencing. A maximum-likelihood phylogeny was constructed using all EV-D68 complete coding sequences available in GenBank (n=482).2662/10 695 (24.9%) were tested positive with EV/RV and 882/2662 (33.1%) were selected randomly and subjected to molecular classification. EV-D68 was detected in 15 (1.70%) samples from patients with clinical presentations ranging from wheezing to pneumonia and belonged to subclade B3. Eight CDSs were successfully obtained. A total of 10 amino acid residue polymorphisms were detected in the viral capsid proteins, proteases, ATPase and RNA polymerase.B3 subclade was the only subclade found locally. Surveillance of EV-D68 raises public awareness and provides the information to determine the most relevant genotypes for vaccine development.