Antigenic and molecular surveillance of influenza virus in the period 1993-1994
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Series / Report no.
Open Access
Type
Report
Language
en
Date
1994-10-31
Research Projects
Organizational Units
Journal Issue
Title
Antigenic and molecular surveillance of influenza
virus in the period 1993-1994
Translated Title
Antigene en moleculaire surveillance van
influenzavirus in de periode 1993-1994
Published in
Abstract
Het influenzavirus ondergaat frequente antigene
veranderingen die jaarlijkse aanpassing van het influenzavaccin noodzakelijk
maken. Voor dit doel coordineert de Wereldgezondheidsorganisatie (WHO) een
mondiaal netwerk van virologische laboratoria. In dit kader vormen de
Erasmus Universiteit Rotterdam (EUR) en het RIVM tezamen het Nationaal
Influenza Centrum (NIC) voor Nederland. De EUR verzamelt recente
influenzavirustammen uit de Nederlandse diagnostische laboratoria,
analyseert deze met serologische en moleculaire technieken, vergelijkt deze
met referentiestammen en met de door de WHO voorgestelde vaccinstammen en
zendt de stammen naar de WHO. Het RIVM voert in samenwerking met NIVEL een
surveillance van respiratoire virusinfecties uit. De hieronder geisoleerde
influenza-virusstammen worden eveneens onderzocht met serologische en
moleculaire technieken en naar de WHO verzonden. Bovendien verzamelt en
analyseert het RIVM influenzavirusstammen uit het buitenland en vergelijkt
deze met de Nederlandse stammen. In de seizoenen 1993 (zuidelijk halfrond
en de tropische landen) en 1993/94 (gematigde streken van het noordelijk
halfrond) werden door het RIVM 207 influenzavirusstammen geanalyseeerd uit
respectievelijk Singapore, Australie, Nieuw Zeeland, Hong Kong, Zuid-Afrika,
Zweden, Noorwegen, Engeland, Frankrijk, Spanje en Nederland. Het betrof in
195 gevallen het subtype A(H3N2) en in 12 gevallen het type B. De
H3N2-virusstammen behoorden alle tot de nieuwe groep varianten, waarvoor het
A/Beijing/32/92-virus de referentiestam is. Deze groep circuleerde ook al
op kleine schaal in de eerste helft van 1993 met ongeveer dezelfde antigene
eigenschappen. De in 1993/94 in Nederland geisoleerde virusstammen waren
serologisch gelijk aan die uit het buitenland. Ze konden in drie varianten
worden onderverdeeld. De hoofdvariant maakte 95% van het totale stammen
uit. Deze variant verschilde sterk van de hoofdvariant van de epidemie van
1991/92 en ontmoette, omdat de H3N2-epidemie van 1992/93 beperkt van omvang
was geweest, slechts betrekkelijk weinig specifieke weerstand onder de
bevolking. Dit droeg waarschijnlijk bij tot de hoge extra mortaliteit van
circa 6200 gevallen die het Centraal Bureau voor de Statistiek voor
Nederland in de laatste maanden van 1993 registreerde. Een andere factor
hierbij zal zijn geweest dat de antigeenstructuur van het vaccinvirus
A/Beijing/32/92 enige mate afweek van de bovengenoemde in Nederland en
elders in 1993 en 1994 circulerende hoofdvariant van het H3N2-virus.
Vermoedelijk heeft het vaccin daardoor in het seizoen 1993/94 geen optimale
bescherming tegen influenza geboden.
In order to formulate recommendations for the annual review of the influenza vaccine composition, the World Health Organization (WHO) coordinates a global network of virological laboratories. In this framework, the Erasmus University of Rotterdam (EUR) and RIVM together form the National Influenza Centre (NIC) of the Netherlands. EUR collects recent influenza virus strains isolated in the Dutch diagnostic laboratories, analyses them by serological and molecular methods, compares them with reference strains and with the vaccine strains proposed by WHO, and sends them to WHO. RIVM isolates influenza viruses in the NIVEL/RIVM surveillance of respiratory virus infections, sends them to WHO, and collects recent influenza virus strains from abroad. At RIVM, the foreign strains are examined with serological and molecular methods and compared with the Dutch virus strains. Of the seasons 1993 (southern hemisphere and tropical countries) and 1993/94 (temperate areas of the northern hemisphere), the influenza epidemics were almost exclusively caused by subtype A(H3N2). Of this period, 207 influenza virus strains originating from Singapore, Australia, New Zealand, Hong Kong, South Africa, Sweden, Norway, United Kingdom, France, Spain, and the Netherlands were analyzed. Of this collection, 195 strains belonged to subtype A(H3N2) and 12 to type B. All the H3N2 virus strains were related to the vaccine strain n/Beijing/32/92. This lineage of strains dates back to the sporadically circulating H3N2 virus strains of 1990. In this report a detailed picture is presented of the antigenic and molecular evolution of this lineage and of another, now (perhaps temporarily) extinct lineage. In 1993/94, we could distinguish three antigenic variants of A/Beijing/32/92-like H3N2 viruses. The main variant comprised 95% of the total number of tested strains. Haemagglutination inhibition (HI) tests indicated that this variant differed widely from the main variant of the previous large epidemic of H3N2 virus (1991/92), implying that the existing group immunity to this variant was very low in the human population. This may have contributed to the high excess mortality of 6200 cases registered during the influenza epidemic of 1993/94. The main variant was related to the 1993/94 vaccine strain A/Beijing/32/92. Still, the differences observed in HI assays suggest that the vaccine induced a less - than - optimal protection against influenza during the last season. With regard to influenza B virus, no significant antigenic changes could be detected when comparing the 1993/94 strains with the strains of 1990/91 and 1992/93.
In order to formulate recommendations for the annual review of the influenza vaccine composition, the World Health Organization (WHO) coordinates a global network of virological laboratories. In this framework, the Erasmus University of Rotterdam (EUR) and RIVM together form the National Influenza Centre (NIC) of the Netherlands. EUR collects recent influenza virus strains isolated in the Dutch diagnostic laboratories, analyses them by serological and molecular methods, compares them with reference strains and with the vaccine strains proposed by WHO, and sends them to WHO. RIVM isolates influenza viruses in the NIVEL/RIVM surveillance of respiratory virus infections, sends them to WHO, and collects recent influenza virus strains from abroad. At RIVM, the foreign strains are examined with serological and molecular methods and compared with the Dutch virus strains. Of the seasons 1993 (southern hemisphere and tropical countries) and 1993/94 (temperate areas of the northern hemisphere), the influenza epidemics were almost exclusively caused by subtype A(H3N2). Of this period, 207 influenza virus strains originating from Singapore, Australia, New Zealand, Hong Kong, South Africa, Sweden, Norway, United Kingdom, France, Spain, and the Netherlands were analyzed. Of this collection, 195 strains belonged to subtype A(H3N2) and 12 to type B. All the H3N2 virus strains were related to the vaccine strain n/Beijing/32/92. This lineage of strains dates back to the sporadically circulating H3N2 virus strains of 1990. In this report a detailed picture is presented of the antigenic and molecular evolution of this lineage and of another, now (perhaps temporarily) extinct lineage. In 1993/94, we could distinguish three antigenic variants of A/Beijing/32/92-like H3N2 viruses. The main variant comprised 95% of the total number of tested strains. Haemagglutination inhibition (HI) tests indicated that this variant differed widely from the main variant of the previous large epidemic of H3N2 virus (1991/92), implying that the existing group immunity to this variant was very low in the human population. This may have contributed to the high excess mortality of 6200 cases registered during the influenza epidemic of 1993/94. The main variant was related to the 1993/94 vaccine strain A/Beijing/32/92. Still, the differences observed in HI assays suggest that the vaccine induced a less - than - optimal protection against influenza during the last season. With regard to influenza B virus, no significant antigenic changes could be detected when comparing the 1993/94 strains with the strains of 1990/91 and 1992/93.
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