Clinical and epidemiological surveillance of influenza and other Acute Respiratory Infections (ARI) are currently a major objective of Public Health. The aim was to describe the epidemiology of influenza using the Italian surveillance system. Vaccination Coverage (VC) rates were calculated during 1999-2009 influenza seasons. Molecular studies of influenza virus isolated, from patients with ILI, living in Apulia, are described. 1269 nasal-pharyngeal swabs were taken from patients with ILI and ARI in order to isolate and identify viruses using PCR. Influenza isolates are typed as being types A and B and influenza A isolates are A/H1 and A/H3. The progression of the ILI cases registered in Apulia was similar to the data recorded on a national level. The VC data recorded in Apulia showed a progressive increase in the vaccine doses administered to subjects over 65 years old. The virological surveillance showed a major circulation of the type A/H3N2 influenza virus during the peak incidence of the illness in seasons 1999-2000, 2002-2003, 2004-2005 and 2008-2009. During the same period, the lowest incidence was registered when the type A/H1N1 and B viruses were in circulation. In contrast, during the other seasons the lowest incidence was reported with A/H3N2 and B viruses. 1. Introduction Influenza remains thus far a serious problem for many countries in connection with the worldwide spread of this disease [1]. Influenza virus infection is an important cause of respiratory infection in the population over the winter season, with peaks in Italy, from the end of December to the middle of March. Influenza strikes all age groups of the population but has a higher incidence in children and adolescents and causes a considerable increase in medical examinations and admissions to hospital. During epidemics, the highest number of complications and more than 90% of deaths associated with influenza are recorded in the elderly (>65 years old) [2, 3]. The virological basis of the frequent epidemics is related to the fact that influenza viruse can quickly mutate within their own antigenic structure. Changes can occur in surface glycolproteins, haemagglutinin and/or neuraminidase, producing new virus strains against with the population has no immunity [4]. For example, the recent emergence of H1N1 (swine flu) illustrates the ability of the influenza virus to create antigens new to the human immune system, even within a given hemagglutinin and neuraminidase subtype [5–7]. The high variability of influenza viruses makes it necessary to carry out comparative research of the
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