[Detection of influenza virus infections by molecular and immunofluorescence methods]

Influenza virus infections are extremely important for human health due to the occurence of seasonal epidemics and pandemics worldwide. Influenza is associated with high morbidity and may result in serious complications such as life threatening viral or bacterial pneumonia. Especially, young children, older adults, patients with chronic diseases such as heart, lung, kidney, and diabetes and immunosuppressed people are at higher risk for complications and death from influenza virus infections. The aim of this study was to determine the incidence of influenza type A and B virus infections and influenza A virus subtypes in hospitalized patients with respiratory tract infections by real-time reverse transcriptase-polymerase chain reaction (RT-PCR, Sacace, Italy), conventional RT-PCR and direct immunofluorescence antibody (DFA, Argene SA, France) tests. Nasopharyngeal swab specimens were collected from a total of 476 patients with respiratory tract symptoms by using flocked swabs (Copan Diagnostics, Italy) between 1 April 2012 and 31 December 2013. Influenza A virus was detected in 20.5% (98/476) and influenza B virus in 3.3% (16/476) of the cases by real-time RT-PCR test. During the study period, 63.3% of 98 influenza virus isolates were found as influenza A(H1N1)pdm09 and 36.7% were influenza A(H3N2) subtypes. Influenza A (H1N1) pdm09 subtype was observed in 12 cases in January 2013 and influenza A(H3N2) subtype was observed in 11 cases in December 2013 as the highest values. When the real-time RT-PCR test was regarded as the reference test, the sensitivities of DFA test for influenza A and B and conventional RT-PCR test with WHO primers (M30F2/08 and M264R3/08) for influenza A were detected as 72.4%, 75%, 96% and the specificities were detected as 99.2%, 99.5% and 100%, respectively. In conclusion, influenza A virus infection was detected rather high with a rate of 20.5% in the study group. The monitoring of influenza virus types and subtypes is required for the evaluation of influenza vaccine strains and circulating influenza viruses and for the identification of subtypes with pandemic potential. Planning for appropriate antiviral therapy using real-time RT-PCR in the early diagnosis of influenza virus infections will significantly contribute to the management of the patient's treatment. Thus, unnecessary drug use will be prevented and controlled with effective treatment of the disease at the time of infection.