Viral genome and antiviral drug sensitivity analysis of two patients from a family cluster caused by the influenza A(H7N9) virus in Zhejiang, China, 2013

• We provided detailed clinical data, epidemiological information of two family cluster patients emerged in Zhejiang, China.
• Genome sequencing and analyses of phylogenetic trees demonstrated that limited human-to-human transmission of the virus probable occurred in the family cluster cases.
• We noted PB2 E627K substitution that was not existed in the isolates of the first wave, as well as two new mutations in the NA gene and six in PB2 gene.
• We observed the reduced sensitivity of the new isolates to oseltamivir.

SummaryObjectivesIn the winter of 2013, people were facing the risk of human-to-human transmission of the re-emerging influenza A(H7N9) virus. We report herein information on the clinical features of two patients from the same family infected with this virus, the genomic sequences of the viruses harbored, and antiviral drug sensitivity.MethodsClinical and epidemiological data of two patients from the same family were collected and analyzed. Sequencing was done for the viruses isolated from these two patients and one epidemiologically related chicken, and the sequences of the eight gene segments of the viruses were analyzed phylogenetically. The sensitivity of the viruses to antiviral drug treatment was determined by neuraminidase inhibitor susceptibility test.ResultsThe two patients from one family cluster shared the same symptoms but had different outcomes, and had a strong epidemiological link. Three strains, two from these two patients and one from the chicken, were isolated. Genome sequencing and analyses of phylogenetic trees demonstrated that the two viruses were almost identical. We noted the presence of the PB2 E627K amino acid substitution that was not present in isolates from the first wave, as well as two new mutations in the NA gene and six in the PB2 gene. Drug sensitivity testing showed that the new isolates were resistant to oseltamivir but sensitive to peramivir.ConclusionsThe two patients from one family cluster were probable human-to-human transmission cases. The new isolates were sensitive to peramivir but showed reduced sensitivity to oseltamivir.