TY - JOUR
T1 - The molecular epidemiology of influenza viruses
T2 - A lesson from a highly epidemic season
AU - D'Agaro, P.
AU - Rossi, T.
AU - Burgnich, P.
AU - Dal Molin, G.
AU - Coppola, N.
AU - Rocco, G.
AU - Campello, Cesare
PY - 2008/3
Y1 - 2008/3
N2 - Aims: To analyse the epidemiological and molecular features of a long-lasting epidemic (12 weeks) of influenza in north-eastern Italy during the 2004-05 season. Methods: Morbidity rates were analysed by time and age. Influenza virus isolates (93 strains) were submitted to antigenic evaluation by haemagglutination inhibition test and to molecular assessment by sequencing. Results: The incidence peak (16.4 per thousand) was the highest recorded over the last six years in north-eastern Italy. The epidemic was sustained by two subsequent waves of circulating viruses: an H3N2 variant and two type B variants, respectively. In addition, scattered isolation of an H1N1 variant occurred. Antigenic and molecular characterisation showed the emergence of an H3N2 virus drifted with respect to vaccine strain, which also had a substantial impact on morbidity in vaccinated subjects. Moreover, a single K145N substitution in the HA1 site of H3N2 was the starting point of two evolutionary branches. No change was observed in H1N1 isolates. B-type virus was mainly represented by Victoria-lineage strains, though Yamagata-lineage viruses were also identified. The fluctuating circulation of these two clades has characterised B virus epidemics in recent years. Conclusions: The assessment of the H3N2 molecular change in this area was in line with results used for establishing the vaccine composition for the incoming season. The particular epidemiological features of two B virus clades, namely Yamagata-like and Victoria-like, may be considered for introduction into the influenza vaccine.
AB - Aims: To analyse the epidemiological and molecular features of a long-lasting epidemic (12 weeks) of influenza in north-eastern Italy during the 2004-05 season. Methods: Morbidity rates were analysed by time and age. Influenza virus isolates (93 strains) were submitted to antigenic evaluation by haemagglutination inhibition test and to molecular assessment by sequencing. Results: The incidence peak (16.4 per thousand) was the highest recorded over the last six years in north-eastern Italy. The epidemic was sustained by two subsequent waves of circulating viruses: an H3N2 variant and two type B variants, respectively. In addition, scattered isolation of an H1N1 variant occurred. Antigenic and molecular characterisation showed the emergence of an H3N2 virus drifted with respect to vaccine strain, which also had a substantial impact on morbidity in vaccinated subjects. Moreover, a single K145N substitution in the HA1 site of H3N2 was the starting point of two evolutionary branches. No change was observed in H1N1 isolates. B-type virus was mainly represented by Victoria-lineage strains, though Yamagata-lineage viruses were also identified. The fluctuating circulation of these two clades has characterised B virus epidemics in recent years. Conclusions: The assessment of the H3N2 molecular change in this area was in line with results used for establishing the vaccine composition for the incoming season. The particular epidemiological features of two B virus clades, namely Yamagata-like and Victoria-like, may be considered for introduction into the influenza vaccine.
UR - http://www.scopus.com/inward/record.url?scp=40449084078&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=40449084078&partnerID=8YFLogxK
U2 - 10.1136/jcp.2007.050005
DO - 10.1136/jcp.2007.050005
M3 - Article
C2 - 17630401
AN - SCOPUS:40449084078
VL - 61
SP - 355
EP - 360
JO - Journal of Clinical Pathology - Clinical Molecular Pathology
JF - Journal of Clinical Pathology - Clinical Molecular Pathology
SN - 0021-9746
IS - 3
ER -