[Influenza surveillance results in 2007-2008 winter season in nine provinces of Turkey]

Abstract

Influenza virus infections constitute a serious public health problem owing to their epidemic and pandemic potential. Turkish Ministry of Health established the national influenza surveillance programme in two institutes to detect the virus types leading to the illness and the efficiency of the seasonal vaccine. Influenza surveillance is performed by Refik Saydam Hygiene Center, National Influenza Laboratory in nine provinces (which are located at central, northeast, south and east parts of Turkey) and by Istanbul University, Medical Faculty, Virology Laboratory in five provinces (which are located at west and northwest parts of Turkey). These two centers are the members of international information networks. The surveillance was aimed to contribute to the detection of influenza viruses with pandemic potential and also to determine the predominant strain circulating in Turkey. During November 2007-May 2008 period a total of 1157 clinical specimens collected from 90 health centers which were the representatives of nine provinces (Ankara, Samsun, Trabzon, Erzurum, Adana, Konya, Diyarbakir, Malatya and Van) were investigated for the presence of influenza virus and other respiratory viruses (Parainfluenza virus types 1-3, Respiratory Synctial Virus and Adenovirus). Samples were identified and subtyped by both molecular (real-time PCR) and cell culture techniques (MDCK and Hep-2). Influenza virus and at least one of the other respiratory viruses were detected in 321 (27.7%) and two different viruses in 16 of the specimens (total= 337). When all the specimens were considered, the most frequently identified virus was influenza A (n=188, 16.2%), H1N1 being 6.3% and H3N2 9.9%.The rate of identification for influenza B was 7.6% (n=88), for parainfluenza was 2.3% (n=27), for adenovirus was 2% (n=24) and for RSV was 0.9% (n=10). When only the positive specimens (n=337) were evaluated, influenza A was again the most frequently (55.7%) encountered virus, H1N1 being 38.8% and H3N2 61.2% of all. Influenza B was in the second rank with 26.1% frequency among the positive specimens. The results showed that influenza activity started around November and ended around May. When the distribution of influenza viruses were analysed according to months, Influenza A H1N1 predominated in January, influenza A H3N2 in December and February. influenza B viruses started to increase in February, and were also detected in May. The 2007-2008 influenza season in Turkey was characterized by moderate clinical activity, and a predominance of influenza A H3N2. These results indicate good match between the vaccine virus strains and the reported virus strains.