Virus characteristics

Details of the distribution of viruses detected in sentinel-source specimens can be found in the Primary care data section.

Viruses detected in non-sentinel source specimens 

For week 44/2018, 148 specimens from non-sentinel sources (such as hospitals, schools, primary care facilities not involved in sentinel surveillance, or nursing homes and other institutions) tested positive for influenza viruses. Of the 148 viruses, 89.9% were type A and 10.1% were type B viruses (Table 2). Of the 43 influenza A viruses that were subtyped, 69.8% were A(H1N1)pdm09 and 30.2% were A(H3N2). None of the influenza B viruses were assigned to a lineage.

Genetic characterization

For week 44/2018, 12 virus genetic characterizations were reported. All were A(H1N1)pdm09 viruses belonging to the A/Michigan/45/2015 (6B.1) clade. The latest characterization data are summarized in the ECDC summary report for September.

For more information on virus characterizations for EU/EEA countries, see earlier WHO CC London Influenza virus characterisation reports.

The recommended composition of the trivalent influenza vaccine for the northern hemisphere 2018–2019 season included an A/Michigan/45/2015 (H1N1)pdm09-like virus, an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus and a B/Colorado/06/2017-like virus (B/Victoria lineage). For quadrivalent vaccines, a B/Phuket/3073/2013-like virus (B/Yamagata lineage) was recommended. The full report can be found here.

On 27 September 2018, WHO announced the recommended vaccine composition for the southern hemisphere 2019 season. The recommendations matched the A(H1N1)pdm09 and B components for the 2018–2019 northern hemisphere season, but the A(H3N2) component was changed for egg-based vaccines. The full report can be found here. A comment by ECDC can be seen here.

Antiviral susceptibility testing

12 A(H1N1)pdm09 viruses with collection dates in weeks 40–44/2018 have been tested for susceptibility to neuraminidase inhibitors. None showed evidence of reduced susceptibility to the inhibitors.