EPIDEMIC RISE IN THE INCIDENCE OF INFLUENZA IN ST. PETERSBURG IN 2016

Abstract

Inf luenza and acute respiratory viral infections (ARVI) account for up to 90% of the total reported infectious morbidity annually in Russia. The economic damage from these infections reaches 86% of the economic losses associated with infectious diseases. As a result of antigenic drift or a shift, new variants of the inf luenza virus, including pandemic strains, appear. In 2009, an inf luenza pandemic arose due to the shifter version of the inf luenza A (H1N1) pdm09 virus. This virus caused epidemic rises of inf luenza in the world in subsequent years. The aim of the study was to describe the epidemic process of inf luenza in January–March 2016 in St. Petersburg. Materials and methods. The incidence of inf luenza and acute respiratory viral infections in St. Petersburg was recorded according to statistical coupons by age groups of the population. Examined nasopharyngeal f lushes received no later than 3–4 days from the onset of the disease, and in case of a lethal outcome — sectional material (bronchi, trachea, lungs, spleen tissues). The detection of RNA of inf luenza viruses was carried out in RT-PCR (Amplicenc Inf luenza virus A/B, Amplicenc Inf luenza virus A/H1-swine-FL, Amplicenc Inf luenza virus A типа-FL, «Interlabservice», Moscow). Isolation of inf luenza viruses from the clinical material was carried out on culture by the MDSC cell. Isolates were typed in RTGA with diagnostic sera to reference and epidemic inf luenza viruses. Isolation of inf luenza viruses from the clinical material was carried out on culture by the MDSC cell. Isolates were typed in RTGA with diagnostic sera to reference and epidemic inf luenza viruses. Results. In 2016, the incidence of inf luenza in St. Petersburg was 81.38 per 100 000 population and was 4.1 times higher than the incidence rate in 2015. The epidemic rise in the incidence of inf luenza and ARVI began with the 3rd calendar week, lasted 6 weeks, with a peak incidence at the 5th calendar week. In total, 398 675 people (7.6% of the population) were ill during this period, including adults — 184 658 (4%), children 0–14 years old — 214 017 or 31.5% of this age group. The greatest number of cases among children was registered in the group of 3–6 years — 87 766 (41.0%). Among the ill children, 86.2% attended pre-school children’s institutions (kindergartens). During the epidemic recovery in 2016, inf luenza viruses were detected in 297 people (46.2%): the inf luenza A (H1N1) virus pdm09 in 97.1% of cases, A (H3N2) — 0.6%, B — 2.3%. There were 102 deaths from complications after the inf luenza, including 101 cases of inf luenza A (H1N1) and A (H3N2) inf luenza A (H1N1) pdm09 confirmed by PCR. Among the dead 101 adults (including 2 pregnant women) and one child. All of them were not vaccinated against the f lu earlier. All deceased adults suffered from chronic physical illnesses.

Keywords

• influenza morbidity
• epidemic process
• influenza viruses
• age distribution
• virological method