Emergence of a novel subclade of influenza A(H3N2) virus in London, December 2016 to January 2017.

We report the molecular investigations of a large influenza A(H3N2) outbreak, in a season characterised by sharp increase in influenza admissions since December 2016. Analysis of haemagglutinin (HA) sequences demonstrated co-circulation of multiple clades (3C.3a, 3C.2a and 3C.2a1). Most variants fell into a novel subclade (proposed as 3C.2a2); they possessed four unique amino acid substitutions in the HA protein and loss of a potential glycosylation site. These changes potentially modify the H3N2 strain antigenicity

The use of whole genome sequencing in the investigation of a nosocomial influenza virus outbreak

Traditional epidemiological investigation of nosocomial transmission of influenza involves the identification of patients who have the same influenza virus type and who have overlapped in time and place. This method may miss-identify transmission where it has not occurred or miss transmission when it has. We applied influenza virus whole genome sequencing (WGS) to an outbreak of influenza A in a haematology/oncology ward and identified two separate introductions; one which resulted in 5 additional infections and 79 bed-days lost. Results from WGS are becoming rapidly available and may supplement traditional infection control procedures in the investigation and management of nosocomial outbreaks