key: cord-1033369-hg3aky1y
authors: Kowalczyk, D.; Szymański, K.; Cieślak, K.; Hallmann-Szelińska, E.; Brydak, L. B.
title: Respiratory Infections with Particular Emphasis on Influenza Virus Activity in Persons Over 14 Years of Age in the Epidemic Season 2016/2017 in Poland
date: 2018-06-20
journal: Current Trends in Immunity and Respiratory Infections
DOI: 10.1007/5584_2018_224
sha: c4ced20e05b492ccad0924bd1bb48bd2458b5077
doc_id: 1033369
cord_uid: hg3aky1y

Influenza viruses cause respiratory infections every epidemic season regardless of the patient’s age. The aim of this study was to determine the activity of respiratory viruses in the epidemic season 2016/2017 in Poland, with particular emphasis on influenza viruses among people aged over 14. There were 2982 clinical samples taken from patients from four age groups: 15–25, 26–44, 45–64, and ≥ 65 years tested under the Sentinel and non-Sentinel surveillance programs. The presence of influenza viruses was confirmed in more than 40% of cases, the predominant type was influenza A virus unsubtyped, followed by subtype A/H3N2/. The results for the four age groups indicate that the highest number of confirmed respiratory viruses was recorded in individuals ≥65 years of age, slightly less, in the decreasing order, in the age groups 45–64 years, 15–25 years, and 26–44 years. Influenza type B infections were observed only in sporadic cases. Given the epidemiological data, epidemic season 2016/2017 was characterized by similar dynamics compared to the previous season in Poland and also in most of the European countries. More than 4 million cases and suspected cases of influenza and influenza-like viruses have been reported in Poland, more than 16,000 hospitalizations, and 25 deaths, of which 20 cases occurred among people ≥65 years of age in the epidemic season 2016/2017.

Infections caused by influenza A and B viruses are observed each season, and the course of illness may differ from one another (Brydak 2008) . In each case, however, quick confirmation of the presence of the influenza virus is important since inappropriately treated infections can lead to sometimes deadly complications, especially among people from the risk groups (Fiore et al. 2011) . Generally, the diagnostic process is carried out using molecular biology methods (Bednarska et al. 2016b) , which allows the obtaining of results promptly. The use of antiviral treatment with neuraminidase inhibitors reduces the risk of complications, also often emanating from the respiratory tract (Bednarska et al. 2015; Brydak 2015) . The epidemic season 2016/2017 in Poland was characterized by a high incidence of influenza and influenza-like illness (ILI) (4,919,110) and of the number of hospitalizations (16, 890) . The number of deaths due to complications amounted to 25 cases in persons over 14 years of age, out of which 20 cases were reported in persons older than 65 years (NIPH-NIH 2017). The influenza activity was rather moderate with the peak incidence of ILI at week 4 of 2017, whereas the highest number of confirmed influenza viruses was observed at week 3 of 2017. Not without significance remains the fact that the proportion of population in Poland vaccinated against influenza is declining in Poland season by season. In 2016, only 2.48% people aged over 14 and 6.87% people aged over 65 were vaccinated, the proportions comparable to those in the preceding year (EPIMELD 2016). The dismal influenza vaccination coverage rate is particularly relevant in the face of a clearly increasing incidence of respiratory infections in adult persons in recent years. The aim of the present study was to evaluate the activity of influenza and influenza viruses in individuals in the age bracket of 14-65 years in the epidemic season 2016/2017 in Poland.

The study was approved by an institutional ethics committee, and it was conducted in accordance with the Declaration of Helsinki for Human Research. The study material consisted of 2982 clinical specimens taken from patients from four age groups (15-25, 26-44, 45-64, and 65 years) within the Sentinel and non-Sentinel surveillance programs. The specimens were nasal and throat swabs, and bronchial alveolar lavage fluid A conventional multiplex RT-PCR was performed to confirm the presence of influenzalike viruses, using a RV15 OneStep ACE Detection Kit (Seegene; Seoul, South Korea). Specimens were tested for the following respiratory viruses: influenza A and B; adenoviruses (ADV); respiratory syncytial viruses (RSV) A and B; human metapneumovirus (HMPV); human coronavirus (HcoV); human parainfluenza viruses 1, 2, 3, and 4; human bocavirus (HboV); and enteroviruses.

In total 2882 clinical specimens were tested in people aged over 14. (Fig. 2) .

In the season 2016/2017, infections caused by influenza A virus remained prevalent (Fig. 3) , with the highest number of confirmed cases noted in the age group 65 (n ¼ 356). In age groups 45-64 and 26-44 years, infections caused by influenza A unsubtyped amounted to 279 and 230 cases, respectively. The lowest number of confirmed influenza A unsubtyped cases was observed in the age group 15-25 years (n ¼ 86). The presence of influenza virus subtype A/H3N2/ was observed across all age ranges. The highest number of confirmed cases of A/H3N2/ subtype was observed in the age groups 26-44 and 45-64 years, 105 and 104, respectively, slightly lower in the age group 65 years (n ¼ 91), and the lowest in 15-25-year-old subjects (n ¼ 45). There were single cases of influenza B virus, but (Table 1) . During the epidemic season 2016/2017, the number of specimens analyzed to confirm influenza infections was lower than that in the previous seasons. However, the percentage of confirmations among people aged over 14 was higher ( Concerning the age-dependent differences in the type of influenza virus causing infections (Fig. 1) , the highest number of confirmations in 2016/2017 was observed in persons over 65 years of age (49.4%), which was different from 2015/ 2016 when the highest number was in those in the age brackets of 45-64 and 26-44 (Kowalczyk et al. 2017a ). The results are consistent with the data from other EU countries concerning influenza virus infections; the prevalence of A/H3N2/ subtype was noted in the season2016/2017, especially in persons aged over 65, who were most vulnerable to infection, according to the ECDC risk assessment ( Given the increase in the number of infections among the elderly over 65 years of age in the analyzed season 2016/2017, a low percentage of people vaccinated against influenza in Poland appears to be an important factor. Although in many voivodships vaccination for this age group is paid by the marshal's offices, 6.87% of them have been vaccinated (NIC 2017). There also was an alarming increase in the number of deaths due to complications among the elderly, 20 out of the 25 cases in 2016/2017, compared with the 56 out of the 140 influenza-related deaths in the preceding season. This dramatic increase in the proportion of influenza-related deaths in the elderly should signal an urgent need for intensified attempts to increase the vaccination coverage in Poland. According to the recommendations issued by WHO, 15 academic medical societies, and 143 national influenza centers, vaccination is the only and most effective method of preventing influenza complications and deaths (NIC 2017; Grohskopf et al. 2016; Brydak et al. 2012; Brydak 2008) . 

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Novelties in influenza surveillance in Poland

Influenza, pandemic flu, myth or real threat? Rythm

Prophylaxis of influenza in general practice

Implementing an influenza vaccination programme for adults aged 65 years in Poland

European Centre for Disease Prevention and Control. An agency of the European Union

Antiviral agents for the treatment and chemoprophylaxis of influenza -recommendations of the Advisory Committee on Immunization Practices (ACIP)

Prevention and control of influenza with vaccines

Virological characteristic of the 2014/2015 influenza season based on molecular analysis of biological material derived from I-MOVE study

Circulation of antibodies against influenza virus Hemagglutinins in the 2014/2015 epidemic season in Poland

The activity of influenza and influenza-like viruses in individuals aged over 14 in the 2015/2016 influenza season in Poland

Reports on Influenza Morbidity in Poland in 2017

Acknowledgments This work was funded by NIPH-NIH thematic subject 3/EM. The authors would like to acknowledge physicians and employees of the voivodship sanitary epidemiological stations (VSES) participating in the Sentinel and non-Sentinel programs for their input into the influenza surveillance in Poland.

The authors declare no conflicts of interest in relation to this article.