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Influenzaseizoen 2018/2019 in Nederland: een relatief milde epidemie met twee subtypen A- virussen

Fouchier, R., Donker, G., Meijer, A., Hoek, W. van der, Lange, M. de, Koopmans, M. Influenzaseizoen 2018/2019 in Nederland: een relatief milde epidemie met twee subtypen A- virussen Nederlands Tijdschrift voor Medische Microbiologie: 2019, 27(4)
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The influenza epidemic of 2018/2019 started in week 50 of 2018 and lasted 14 weeks. The epidemic reached peak incidence in week 6 of 2019, with 10,8 persons presenting influenza- like ill ness (ILI) per 10.000 inhabitants, marking a relatively mild season.

Influenza A(H1N1)pdm09 and A(H3N2 viruses were detected at approximately equivalent frequencies. The sporadic detection (less than 1 per cent) of influenza B viruses was remarkable.

Approximately 81 percent of the circulating A(H3N2) viruses belonged to clade 3C.2a1b, for which the antigenic similarity to the vaccine strain was fair to good.

Viruses of clade 3C.3a were detected with increasing frequency nationally (17 per cent) and elsewhere, causing a problem for vaccine strain selection. The A(H1N1)pdm09 viruses belonged to genetic clade 6b.1a and displayed good antigenic similarity to the vaccine strain. The vaccine effectiveness against laboratory- confirmed influenza virus infection was 57 percent.

Among 756 viruses tested for sensitivity to neuraminidase inhibitors, three had strongly reduced sensitivity. All tested influenza A vi ruses had the S31N amino acid substitution in M2 responsible for resistance to ionchannel inhibitors.