Virological Surveillance of Influenza in Four Recent Post-Pandemic Seasons (2010/11 to 2013/14) in Bulgaria.

AIM: Influenza virological surveillance is an essential tool for studying the evolution of influenza viruses as well as for annual updating of the vaccine composition. The aim of the present study is to analyse the circulation of the influenza viruses in Bulgaria during the four recent post-pandemic seasons. METHODS: A total of 3,681 respiratory samples from patients with influenza like illness (ILI) or acute respiratory illness (ARI) were tested for influenza viruses using Real Time RT-PCR. RESULTS: Influenza viruses were detected in 1,367 (37%) samples. Of those viruses, 941 (69%) were of type A and 426 (31%) of type B. Among the subtyped A viruses, 543 (60%) were A(H1N1)pdm09 and 369 (40%) A(H3N2). Co-circulation of all seasonal influenza types/subtypes was registered during each season, with the exception of A(H1N1)pdm09 virus in the 2011/12 season. In this study, data gathered from the antigenic and genetic analyses of influenza viruses, their antiviral susceptibility, and the epidemiological and clinical characteristics of the infections are presented. CONCLUSIONS: Yearly variations in the distribution and frequency of influenza types/subtypes and an annual shift of the predominant type/subtype were observed. In the seasons with predominant spread of A(H1N1)pdm09 virus - 2010/11 and 2013/14, a greater number of influenza-related pneumonia cases, ICU admissions and fatal cases was registered (p<0.05). The results of the present study confirm the need for continuous and comprehensive influenza surveillance.

Etiological role of ortho- and paramyxoviruses in acute respiratory tract infections among children aged < 4 years in Bulgaria.

BACKGROUND: Influenza viruses (family Orthomyxoviridae); respiratory-syncytial virus (RSV), human metapneumovirus (hMPV), and parainfluenza viruses (hPIV) type 1, 2 and 3 (family Paramyxoviridae) are among the most common causes of acute respiratory tract infections (ARTI) in infants and young children. The aim of this study was to determine the contribution of these viruses in cases of ARTI requiring medical attention among children aged < 4 years during the 2012/13 and 2013/14 winter seasons in Bulgaria. METHODS: A total of 416 nasopharyngeal swabs of children aged < 4 years presenting ARTI from different regions of country were tested for influenza A/B viruses by real-time RT-PCR. Influenza virus negative samples were examined by individual real-time RT-PCR using specific primers/probes for RSV, hMPV, and hPIV1, 2, and 3. RESULTS: Of the 416 specimens tested, 129 (31%) were influenza virus positive. Influenza A(H1N1)pdm09, A(H3N2), and type B viruses were found in 61 (14.7%), 14 (3.4%), and 49 (11.8%) of samples, respectively. Of the 287 influenza virus negative specimens, paramyxoviruses - RSV, hMPV, hPIV1, hPIV2, and hPIV3 were detected in 55 (19.2%), 28 (9.8%), 17 (5.9%), 5 (1.7%), and 14 (4.9%) samples, respectively. RSV were the most frequently identified paramyxovirus (p < 0.05). Overall, 15 (6.4%) patients were co-infected with two viruses. The contribution of respiratory viruses in cases of bronchiolitis, pneumonia, and neurological complications was analyzed. CONCLUSIONS: Influenza viruses and RSV were the most frequent viral pathogens causing ARTI among children < 4 years of age during the 2012/13 and 2013/14 winter seasons in Bulgaria.

Effect of a plant polyphenol-rich extract on the lung protease activities of influenza-virus-infected mice.

Influenza infection was induced in white mice by intranasal inoculation of the virus A/Aichi/2/68 (H3N2). The lung protease and the protease-inhibitory activities were followed for 9 days after infection. The intranasal application of a polyphenol-rich extract (PC) isolated from Geranium sanguineum L. induced a continuous rise in the anti-protease activity but did not cause substantial changes in the lung protease activity of healthy mice. Influenza virus infection triggered a slight reduction in protease activity in the lungs at 5 and 48 h post infection (p.i.) and a marked increase at 24 h and 6 day p.i.. Protease inhibition in the lungs was reduced at 24 and 48 h p.i. and an increase was observed at 5 h and 6 and 9 days p.i.. PC treatment brought both activities to normal levels. The restoration of the examined parameters was consistent with a prolongation of mean survival time and reduction of mortality rate, infectious virus titre and lung consolidation. PC reinstated superoxide production by alveolar macrophages and increased their number in virus-infected mice. The favourable effect on the protease and the protease-inhibitory activities in the lungs of influenza-virus-infected mice apparently contributes to the overall protective effect of PC in the murine experimental influenza A/Aichi infection. The antiviral effect of the individual constituents was evaluated.