Influenza surveillance in Victoria, 2005
Joy L Turner1, James E Fielding, Hazel J Clothier
1Epidemiology Unit, Victorian Infectious Diseases Reference Laboratory, Melbourne, Victoria.
Abstract:
Influenza activity remained within normal seasonal activity with a well-defined peak at week 29 (beginning 18 July) during the Victorian influenza season from May to September 2005. Surveillance was based on sentinel general practice influenza-like illness (ILI) notifications with laboratory confirmation, medical locum service ILI notifications and laboratory notification of influenza detections. One thousand and eighty-seven consultations for ILI were reported from 38 general practices, while medical practitioners from the locum service reported 317 consultations for ILI. The average weekly rate of ILI from sentinel surveillance was 7.3 per 1,000 consultations. Similar numbers of influenza A subtypes H1N1 and H3N2 were detected; 45 per cent of which were A/California/7/2004-like (H3), 44 per cent were A/New Caledonia/20/99-like (H1) and 11 per cent were A/Wellington/1/2004 (H3). Of the influenza B samples, 67 per cent were B/Hong Kong/330/2001-like and 33 per cent were B/Shanghai/361/2002-like. The influenza vaccine for 2005 contained: A/New Caledonia/20/99(H1N1)-like virus, A/Wellington/ 1/2004(H3N2)-like virus, and B/Shanghai/361/2002-like virus. Although the predominant H3 and B circulating strains were not included in the vaccine, there was reasonable serological cross protection between vaccine and circulating strains.
Insights
Victorian influenza season 2005 saw normal activity with a peak in July. While the influenza vaccine didn't match all circulating strains, reasonable cross-protection was observed.
Area of Science:
- Virology
- Epidemiology
- Public Health
Background:
- Seasonal influenza surveillance is crucial for monitoring viral activity and informing public health strategies.
- Understanding the circulating influenza strains and their relation to vaccine composition is vital for effective disease prevention.
Purpose of the Study:
- To describe the epidemiological and virological characteristics of the 2005 Victorian influenza season.
- To assess the match between circulating influenza strains and the 2005 seasonal influenza vaccine.
Main Methods:
- Surveillance data included general practice and locum service notifications of influenza-like illness (ILI) with laboratory confirmation.
- Influenza virus strains were identified through laboratory detection.
- Serological cross-protection was evaluated between vaccine and circulating strains.
Main Results:
- Influenza activity peaked in July 2005, consistent with normal seasonal patterns.
- Influenza A (H1N1 and H3N2) and B strains circulated, with specific subtypes identified.
- The 2005 vaccine contained A/New Caledonia/20/99 (H1N1), A/Wellington/1/2004 (H3N2), and B/Shanghai/361/2002-like viruses.
- Predominant circulating H3 and B strains were not fully represented in the vaccine.
Conclusions:
- The 2005 Victorian influenza season exhibited typical activity.
- Despite some mismatches, the influenza vaccine provided reasonable serological cross-protection against circulating strains.
- Ongoing surveillance and vaccine composition review remain important for influenza control.
