Influenza and other acute respiratory viral infections are the most common contemporary infectious diseases resulting in prominent harm to human health and great economic damage. At least five groups of viruses including more than 300 subtypes are currently referred to ARVI pathogens. Such infectious agents are characterized by variability resulting in their altered antigenic characteristics, increased contagiousness, "evasion from immune response and resistance to antivirals. Relevance of influenza and other ARVIs is also accounted for by rapid development of bacteria-associated respiratory diseases. Continuous variability of influenza viruses and emergence of new ARVI pathogens pose a serious threat. In recent years, a simultaneous circulation of subtype A (H1N1) and A (H3N2) influenza viruses with a predominance of a pandemic strain as well as type B viruses have been observed. Among the causative agents of non-influenza ARVIs, respiratory syncytial virus, rhino- and adenoviruses, and I/III parainfluenza viruses are recorded most often. Here we present the data of virology and serological examination of clinical samples collected during the 2018 – 2019 epidemic season in the Republic of Kazakhstan. For this, 2794 clinical samples (2530 nasopharyngeal swabs and 264 blood serums) were collected from patients diagnosed with ARVI, ARI, bronchitis, and pneumonia. Analysis of nasopharyngeal swabs for detection of influenza by RT-PCR demonstrated that mixed etiology influenza viruses with predominance of A/H1N1pdm virus circulated in Kazakhstan. The genetic fingerprints of influenza virus were found in 511 swabs (20.20% of total examined samples). Influenza A virus RNA was detected in 508 biological samples: A/H1N1 – in 289, A/H3N2 – in 209, and unidentified virus subtype in 10 samples. Type B influenza virus was detected in 3 samples. Study of 264 serum samples by HAI assay and ELISA showed emergence of antibodies against influenza A/H1N1, A/H3N2, and B viruses in residents from various regions of Kazakhstan that indirectly confirmed co-circulation of these viruses. 42 influenza virus strains were isolated in chicken embryos, from which 28 were assigned to A/H1N1pdm virus, 13 to A/H3N2 virus, and one isolate was identified as influenza B virus. Laboratory diagnostics of clinical samples for ARVIs established that among identified non-influenza agents respiratory syncytial virus dominated, while rhinoviruses and adenoviruses were less common. Metapneumoviruses, bocaviruses, coronaviruses, and type I parainfluenza viruses were detected in few cases. Comparison of study data with those obtained after examining circulation of influenza viruses during the 2017 – 2018 epidemic season showed that in 2018 – 2019 in Kazakhstan similar to the previous epidemic season, influenza A and B viruses continued to circulate, with prevalence of A/H1N1pdm virus. Identification of non-influenza viruses causing respiratory infections in 2018 – 2019 showed predominance of respiratory syncytial virus, which correlated with data on the 2017 – 2018 epidemic season.
Invasive pneumococcal and meningococcal disease: association with influenza virus and respiratory syncytial virus activity?
