RT Journal Article SR Electronic(1) A1 Vuopio-Varkila, J A1 Suppola, J A1 Klinger, N A1 Tarkka, E A1 Kolho, E YR T1 JF VO OP UL https://www.eurosurveillance.org/content/10.2807/esm.02.12.00174-pt