Influenza and Influenza-Like Virus Infection in Children Under 14 Years of Age: An Investigation of 725 Cases in the 2021/2022 Influenza Epidemic Season in Poland.

BACKGROUND Influenza in children poses a significant health problem worldwide. In this study we investigated 725 cases of influenza and influenza-like virus infection in children under 14 years of age in the 2021/2022 influenza epidemic season in Poland. MATERIAL AND METHODS The material for the study (nose and throat swabs) was collected during the 2021/2022 epidemic season. We analyzed 725 samples from the National Influenza Center, Department of Influenza Research at the National Institute of Public Health NIH-NRI or at 16 Voivodship Sanitary Epidemiological Stations across Poland. Quantitative polymerase chain reaction (qRT-PCR) was applied to determine the influenza virus type and subtype (in RNA isolated from positive samples). RESULTS This study shows the high incidence of influenza among children under the age of 14. Most confirmed infections were caused by influenza A. The genetic material of the A/H1N1/pdm09 subtype was not found among the analyzed samples. The highest number of influenza A infections was among the youngest children (the 0-4 years age group). The most common influenza-like virus was respiratory syncytial virus (RSV). The greatest number of cases caused by this respiratory virus was registered among the youngest children (0-4 years). CONCLUSIONS This study, which shows the high incidence of influenza among children under the age of 14, highlights the importance of regular influenza vaccination. Since children often play a dominant role in spreading influenza virus in the community, regular vaccination can have both health and economic benefits for all age groups.

Analysis of Infections Caused by Influenza Viruses and Influenza-Like Viruses in the Population of People over 65 Years of Age in the 2019-2020 Epidemic Season in Poland.

BACKGROUND Influenza can be the most dangerous for people in risk groups, for example for seniors, in whom it can lead to serious and life-threatening complications. The aim of this research was to analyze the activity of influenza viruses and influenza-like viruses in patients over 65 years of age in the 2019-2020 epidemic season in Poland. MATERIAL AND METHODS A total of 1269 samples collected from patients over 65 years of age with suspected influenza or other respiratory viruses in the 2019-2020 epidemic season (from October 1, 2019, to September 30, 2020) were analyzed. The test material was nose and throat swabs collected during the 2019-2020 epidemic season. Quantitative polymerase chain reaction was used to determine the influenza virus type and subtype for positive samples. RESULTS Among the confirmed infections with influenza viruses, cases due to influenza A were dominant, and the dominant subtype was influenza A subtype A/H1N1/pdm09. Infections with influenza-like viruses were also confirmed in the patients participating in the study, with the presence of genetic material of respiratory syncytial viruses confirmed most often. CONCLUSIONS Seasonal vaccinations can significantly reduce the number of cases and thus the risk of post-influenza complications and deaths among seniors. This is very important, especially now, due to the current epidemiological situation related to the ongoing SARS-CoV-2 respiratory virus pandemic.

Epidemiology of Influenza Viruses and Viruses Causing Influenza-Like Illness in Children Under 14 Years Old in the 2018-2019 Epidemic Season in Poland.

BACKGROUND This study aimed to investigate the epidemiology of influenza viruses and viruses that caused influenza-like disease in children under 14 years of age in the 2018-2019 epidemic season in Poland, and to identify the public health lessons that can be learned. MATERIAL AND METHODS Nose and throat swabs were used to obtain samples. The samples were analyzed in the National Influenza Center, Department of Influenza Research at the National Institute of Public Health-National Institute of Hygiene as well as in 16 Voivodship Sanitary Epidemiological Stations across the country. Methods of RNA isolation depended on the laboratory where the isolation was performed. In all laboratories, quantitative polymerase chain reactions were used to determine the influenza virus type as well as the subtype. RESULTS The study group was confirmed to be infected with influenza A and B, with influenza A/H1N1/pdm09 as the dominant subtype. Among the age group of children up to 14 years of age, cases of infection with viruses that cause influenza-like disease were also reported. It was noticeable that the largest number of confirmed cases of infection was recorded in the group of the youngest children (0-4 years). In addition, several different variants of co-infection were registered. CONCLUSIONS This population study showed that in the 2018-2019 epidemic season in Poland children aged under 14 years were at risk of influenza virus infection and its complications. The presented data support increasing the percentage of children being vaccinated in Poland.

Subtypes of Influenza Virus Infection and Outcomes in Individuals Older than 65 Years of Age in Poland in the 2016/2017 to 2019/2020 Epidemic Seasons.

BACKGROUND Influenza is a viral disease causing many deaths each season. With aging, the human immune system becomes weaker, so people over the age of 65 years are at higher risk of complications after influenza infections. This population study, conducted in Poland, aimed to identify the subtypes of influenza virus infection and outcomes in individuals more than 65 years of age in the 2016/2017 to 2019/2020 epidemic seasons. MATERIAL AND METHODS The research materials were nose and throat swabs. Research was conducted in 16 Voivodship Sanitary and Epidemiological Stations and in the Department of Influenza Research, National Influenza Centre, NIPH-NIH. Methods of RNA isolation depended on the laboratory where the isolation was performed. In all laboratories, quantitative polymerase chain reaction (qRT-PCR) was used to determine the influenza virus type and subtype. RESULTS The analysis of the incidence of influenza among people over the age of 65 included the 2016/2017, 2017/2018, 2018/2019, and 2019/2020 influenza epidemic seasons. We analyzed the percentage of positive samples, the dynamics of epidemic seasons, and the percentage share of influenza viruses in the 65+ age group, according to the epidemic season and percentage of deaths. CONCLUSIONS This population study showed that, in Poland, between the 2016/2017 and 2019/2020 epidemic seasons, people who were more than 65 years of age were at higher risk of influenza virus infection and its complications. The findings support the importance of seasonal influenza vaccination in the population over age 65 years.

Influenza and Influenza-Like Respiratory Virus Infections in Children During the 2019/20 Influenza Seazon and the COVID-19 Pandemic in Poland: Data from the Department of Influenza Research, the National Influenza Center at the National Institute of Public Health, National Institute of Hygiene-National Research Institute and 16 Voivodeship Sanitary and Epidemiological Stations

BACKGROUND This population study aimed to investigate influenza and influenza-like respiratory virus infections in children during the 2019/20 influenza season and the coronavirus disease 2019 (COVID-19) pandemic in Poland. MATERIAL AND METHODS This study analyzed data from the National Influenza Centre, the Department of Influenza Research at the National Institute of Public Health, and 16 Voivodeship Sanitary and Epidemiological Stations in Poland. Nose and throat swabs were obtained from children during the 2019/20 influenza season and the COVID-19 pandemic. Viral RNA detection was performed using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to diagnose influenza virus infection and viral subtypes. RESULTS In the analyzed group, both cases of influenza A and B and infections with influenza-like viruses were confirmed. Among all cases caused by influenza viruses, influenza A was more frequent than B, with predominance of the A/H1N1/pdm09 subtype. The flu-like virus which infected most children was the human respiratory syncytial virus (RSV). The greatest number of cases with RSV was registered in the group of the youngest children (0-4 years). CONCLUSIONS This population study from Poland showed that during the COVID-19 pandemic, and during the winter influenza season of 2019/20, influenza and influenza-like viral infections in children showed some differences from previous influenza seasons. The findings highlight the importance of viral infection surveillance and influenza vaccination in the pediatric population.

Prevalence of circulating antibodies against hemagglutinin of influenza viruses in epidemic season 2021/2022 in Poland.

The aim of the study was to determine the level of anti-hemagglutinin antibodies in the serum of patients during the 2021/2022 epidemic season in Poland. A total of 700 sera samples were tested, divided according to the age of the patients into 7 age groups: 0-4 years of age, 5-9 years of age, 10-14 years of age, 15-25 years of age, 26-44 years of age, 45-64 years of age and ≥65 years of age, 100 samples were collected from each age group. Anti-hemagglutinin antibody levels was determined using the haemagglutination inhibition assay (OZHA). The results obtained confirm the presence of anti-hemagglutinin antibodies for the antigens A/Victoria/2570/2019 (H1N1) pdm09, A/Cambodia/e0826360/2020 (H3N2), B/Washington/02/2019 and B/Phuket/3073/2013 recommended by World Health Organization (WHO) for the 2021/2022 epidemic season. The analysis of the results shows differences in the levels of individual anti-hemagglutinin antibodies in the considered age groups. In view of very low percentage of the vaccinated population in Poland, which was 6.90% in the 2021/2022 epidemic season, the results obtained in the study would have to be interpreted as the immune system response in patients after a previous influenza virus infection.

The Impact of the COVID-19 Pandemic on Influenza Transmission in Poland.

BACKGROUND: The aim of this study was to determine whether the occurrence of the SARS-CoV-2 pandemic affected the incidence of influenza in Poland and the efficiency of the SENTINEL influenza surveillance system. METHODS: The analysis was based on virologic data from the 2018/2019-2021/2022 epidemic seasons. The data in question were obtained from the SENTINEL influenza surveillance system, which is utilized in Poland. RESULTS: In the 2020/2021 epidemic season, only one positive case was confirmed. In the epidemic season of 2021/2022, the number of positive cases increased. There was a delay in the peak of the season, since the start of pandemic, which was observed in the 14th week of 2022. Previously, it was recorded in the 5-10th week, depending on the season. Before the pandemic, the number of positive samples in relation to the tested ones oscillated between 41-49.4%. After the pandemic, it was 0.3% and below 20%, respectively, for season 2020/2021 and season 2021/2022. CONCLUSIONS: The COVID-19 pandemic caused a decline in many other infectious diseases, including influenza, as a result of the numerous lockdowns and from people shifting to remote work. Other safety measures, such as obligatory protective masks and the use of disinfectants, had a significant impact on reducing the number of cases.

Seasonal and inter-seasonal RSV activity in the European Region during the COVID-19 pandemic from autumn 2020 to summer 2022.

Background: The emergence of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in early 2020 and subsequent implementation of public health and social measures (PHSM) disrupted the epidemiology of respiratory viruses. This work describes the epidemiology of respiratory syncytial virus (RSV) observed during two winter seasons (weeks 40-20) and inter-seasonal periods (weeks 21-39) during the pandemic between October 2020 and September 2022. Methods: Using data submitted to The European Surveillance System (TESSy) by countries or territories in the World Health Organization (WHO) European Region between weeks 40/2020 and 39/2022, we aggregated country-specific weekly RSV counts of sentinel, non-sentinel and Severe Acute Respiratory Infection (SARI) surveillance specimens and calculated percentage positivity. Results for both 2020/21 and 2021/22 seasons and inter-seasons were compared with pre-pandemic 2016/17 to 2019/20 seasons and inter-seasons. Results: Although more specimens were tested than in pre-COVID-19 pandemic seasons, very few RSV detections were reported during the 2020/21 season in all surveillance systems. During the 2021 inter-season, a gradual increase in detections was observed in all systems. In 2021/22, all systems saw early peaks of RSV infection, and during the 2022 inter-seasonal period, patterns of detections were closer to those seen before the COVID-19 pandemic. Conclusion: RSV surveillance continued throughout the COVID-19 pandemic, with an initial reduction in transmission, followed by very high and out-of-season RSV circulation (summer 2021) and then an early start of the 2021/22 season. As of the 2022/23 season, RSV circulation had not yet normalised.

Spread of Influenza Viruses in Poland and Neighboring Countries in Seasonal Terms.

In Poland, flu supervision is coordinated by the National Influenza Center at the National Institute of Public Health-National Institute of Hygiene. In this publication, we want to determine geographical trends in influenza virus circulation in the region. A detailed analysis of virological and epidemiological data showed the course of the epidemic season in Poland, as well as in neighboring countries. The spatial differentiation of the incidence of infection between voivodships was examined, as well as compared to countries that border a given voivodship. The results show a significant variation in the incidence of infection in terms of time and space. This points to the need to increase the number of tests and to raise awareness among health care professionals and the public about the probability of an influenza pandemic, as undetected viruses can spread further into the European Union.

Hemagglutination inhibition antibody titers as a correlate of protection against influenza disease in the 2018/2019 epidemic season in Poland.

The aim of this study was to determine the level of antibodies against hemagglutinin of influenza viruses in the sera of people in the seven age groups in the epidemic season 2018/2019 in Poland. The level of anti-hemagglutinin antibodies was determined by hemagglutination inhibition test (HAI). 1050 clinical samples from all over the country were tested. The level of antibodies against influenza viruses was highest in the 10-14 age group for A/Singapore/INFIMH-16-0019/2016 (H3N2) and B/Phuket/3073/2013 Yamagata lineage antigens. These results confirm the circulation of four antigenically different influenza virus strains, two subtypes of influenza A virus - A/Michigan/45/2015 (H1N1)pdm09 and A/Singapore/INFIMH-16-0019/2016 (H3N2) and two lineages of influenza B virus - B/Colorado/06/2017 - Victoria lineage and B/Phuket/3073/2013 Yamagata lineage.