Original scientific paper
Epidemiological and virological surveillance of influenza and influenza like illness in Slovenia
Katarina Prosenc
Maja Sočan
Abstract
The number of patients with acute respiratory infections rises sharply shortly after the influenza virus appears in population. Consequently, the hospitalization and mortality rates increase. Several indicators may be used to measure the burden-of-illness caused by the influenza virus: incidence rate of influenza-like illness (ILI) or acute respiratory illness (ARI), crude or cause-specific mortality rate, sick-live or monitoring the over the counter (OTC) medication sales. Two indicators have been measured in Slovenia since 1999: the ILI and ARI incidence rates in approximately 4% of the population.
Multiplex Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was used as a screening method for the detection of influenza viruses, respiratory syncytial virus (RSV), adenoviruses and enteroviruses in nasal and/or throat swabs. All positive samples were further propagated in the corresponding cell culture line. RT-PCR was used for fast determination of hemaglutinins (H1, H3) and neuraminidases (N1, N2) of influenza A viruses. The antigenic subtype of the samples isolated on the cell culture was determined by means of a hemaglutination inhibition assay and confirmed in the WHO European Reference Centre for Influenza. In the 2004/2005 season, the ILI incidence rate was at highest in weeks 5, 6 and 7 of the year 2005, when it reached its peak value (392/100,000). The highest ARI incidence rate was recorded in the period from 31st January to 6th February, and remained elevated for the following two weeks. Samples were taken from 793 patients with clinical signs of ILI. The influenza A or B virus was detected in 15.2% of patients. One third of the influenza A cases were of the H1N1 subtype, while the others were H3N2. Enteroviral infection was relatively common in the past season (15.8% of patients). The influenza isolates in Slovenia were similar to those in other European countries and belonged to: A/H3N2/California/7/2004 (A/H3N2/Fujian/441/2002-like viruses), A/H1N1/New Caledonia/20/99 and B/Jiangsu/10/03 (B/Shaghai/361/2002-like viruses).
The dominant influenza virus in Europe and the USA was influenza A H3N2. The ARI and/or ILI incidence rates were higher in most European countries (including Slovenia) compared to previous seasons.
Keywords
Influenza-like illness; Acute respiratory infections; Sentinel surveillance; Influenza A; Influenza B; Multiplex RT-PCR
Hrčak ID:
7742
URI
Publication date:
25.11.2006.
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