Application of Molecular Biology Methods for Detection of Influenza Viruses in Bulgaria

Influenza viruses A and B are world-wide major causative agents of human acute respiratory infections. Three subtypes of HA (H1 to H3) and two subtypes of NA (N1 and N2) are found among influenza A viruses that have caused epidemics and pandemics among humans. For the rapid isolation and identification of influenza viruses in clinical samples variety of methods are available but the use of nucleic acid amplification techniques like RT-PCR has made sensitive diagnosis of influenza virus infection feasible, with the possibility of type and subtype determination. During the season 2002/2003 the laboratory of Influenza and ARD detected 7 type A and 4 type B influenza viruses by RT-PCR in 15 simulated samples from the respiratory panel from SEQC. In the season 2003 /2004 42 positive results for influenza viruses subtype А/Н3N2/ were obtained by RT-PCR using specific НA and NA primer pairs from 50 nasal and throat swabs from patients with influenza-like diseases. The RT-PCR provides a sensitive and specific method for detecting, typing and subtyping influenza viruses A and B in clinical samples and can be used in the routine diagnosis of the disease in Bulgaria together with a large complex of classical methods.