Epidemiological Characteristics Of Influenza Research Articles

Flu yesterday, today and tomorrow. The results of monitoring immunization and morbidity in the epidemic seasons 2019–2020, 2020–2021, 2021–2022, 2022–2023

BACKGROUND: This study presents the epidemiological characteristics of influenza in the last four influenza seasons across the years 2019–2023 The analysis of vaccination and morbidity monitoring data have shown the high effectiveness of influenza vaccine prophylaxis. The influenza vaccines registered in Russia are considered, and their features, composition, and advantages are indicated. Recommendations for their use are provided, including aspects of vaccination of persons belonging to risk groups.
 AIM: This study aimed to analyze the epidemiological features of influenza seasons in 2019–2020, 2020–2021, 2021–2022, and 2022–2023, and evaluate the effectiveness of domestic influenza vaccines in mass immunization of the Russian population.
 MATERIALS AND METHODS: Information from the official website of the Research Institute of Influenza of the Ministry of Health of the Russian Federation, data from the state report “On the State of Sanitary and Epidemiological Welfare of the Population in the Russian Federation” for 2021 and 2022, materials from conferences and congresses on influenza, and information and analytical certificates from the Ministry of Health of the Russian Federation were evaluated. Monitoring included the rapid collection, analysis, synthesis of information on immunization in the Russian Federation (in different age, social, and professional groups of the population), and analysis of influenza incidence, among others. Preventive effectiveness was determined by the following indicators: morbidity per 100,000 population, efficiency index (K) expressed in conventional units (units), and efficiency coefficient (protection) (E) expressed in %.
 RESULTS: The COVID-19 pandemic had significantly affected the quantitative characteristics of seasonal influenza epidemics. In the influenza seasons 2020–2021 and 2021–2022, the predominance of the SARS-CoV-2 virus resulted in the temporary “displacement” of influenza viruses from the human population, and influenza incidence decreased to a historical minimum (0.07 per 100,000 population) in 2020–2021. In the epidemic season 2022–2023, high activity of influenza viruses was noted with the continued high coverage of immunization against influenza in the Russian Federation population (52.8%). The incidence rate of influenza in 2022–2023 was 60.80 per 100,000 people. The incidence among those vaccinated was only 4.23 per 100,000 people, which confirms the effectiveness of vaccination. The etiological structure was dominated by the influenza A(H1N1)pdm09 virus. Of 149,000 cases of registered influenza (with laboratory confirmation, 136,600 cases), 3,276 people (2% of the number of cases) were vaccinated. Most patients had concomitant diseases.
 CONCLUSIONS: In the post-pandemic period, against the background of simultaneous circulation of influenza viruses and SARS-CoV-2, an increase in morbidity, caused primarily by influenza A viruses, is expected. Seasonal vaccination is a strategy to ensure the protection of the population from influenza. Annual immunization against influenza with coverage of at least 40% of all social and professional groups of the population remains effective in reducing the severe forms of diseases and mortality. Vaccination helps avoid an increase in morbidity and mass hospitalization and thus significantly reduces the burden on the healthcare system. Special attention should be paid to vaccination of pregnant, people aged 60 years and patients with chronic diseases.

A 1-year cross-sectional study on the predominance of influenza among hospitalized children in a tropical area, Kota Kinabalu, Sabah

BackgroundChildren are at higher risk of influenza virus infection, and it is difficult to diagnose. They are also responsible for the transmission of influenza because of their longer viral shedding compared to adults. In Malaysia, studies on influenza in children are scarce, and as a result, policy decisions cannot be formulated to control the infection. Hence, the objective of this study is to determine the prevalence and epidemiological characteristics of influenza among children with upper respiratory symptoms in the Sabah state of Malaysia.MethodsA cross-sectional study with a simple random sampling was conducted among children with upper respiratory symptoms in Sabah from 1 March 2019 to 29 February 2020. Patients admitted to a pediatric ward of Sabah Women and Children’s Hospital who presented with a fever >38 °C and cough within 48 h of admission were enrolled in this study. A nasopharyngeal swab was taken, and influenza was diagnosed by lateral flow test. Clinical features of influenza-positive children were compared with children whose results were negative.ResultsA total of 323 nasopharyngeal samples were collected, and 66 (20.4%) of them were positive for influenza. Fifty-six (85%) were infected by influenza A whereas ten (15%) were by influenza B virus. Higher temperature (aOR 2.03, 95% CI 1.296–3.181), less activity (aOR 2.07, 95% CI 1.158–3.693), and seizure (aOR 4.2, 95% CI 1.614–10.978) on admission were significant risk factors associated with influenza in children. Meteorology parameters such as humidity and rainfall amount were statistically significant at 95% CI [1.133 (1.024–1.255)] and 95% CI [0.946 (0.907–0.986)].ConclusionThe prevalence of influenza was high among children with upper respiratory symptoms, and they were infected predominantly with the influenza A virus. Children presented with seizures, less activity, and fever were the significant risk factors for influenza. Influenza vaccination should be prioritized as preventive measures for children.

Clinico-epidemiological profile of Influenza A H1N1 cases at a tertiary care institute of Uttarakhand.

Introduction:The swine (H1N1) virus responsible for worldwide pandemics since 2009 is now causing seasonal epidemics. Since then alarming spikes of swine flu cases have been reported from Uttarakhand every year. There are limited studies conducted in this Himalayan belt to evaluate the clinical and epidemiological profile of the patients admitted in tertiary care hospitals.Aims & Objectives:This study aims to summarize the clinical and epidemiological attributes of swine flu and to approximate the burden of Influenza A H1N1 (Swine Flu) cases in this Himalayan belt.Material and Methods:Clinical and epidemiological characteristics of influenza A H1N1 cases from October 2018 to April 2019 were retrospectively and descriptively analyzed using data from the Medical Records Section and the isolation ward at Shri Guru Ram Rai Institute of Medical and Health Sciences; Shri Mahant Indiresh hospital.Results:A total of 1126 (51.6%) patients were tested of which 30% (338) patients were found to be H1N1 positive. Maximum cases and positivity were detected in the months of January (26.4%), February (50.3%), and March (14.8%), and the patients in the age groups of 41–50 (21.9%) and 51–60 years (19.3%) accounted for majority of the cases. The most common symptoms were fever (85.8%), cough (82.2%), sore throat (82%), and breathlessness (71.3%). A case fatality ratio of 10.9% was observed. A significant statistical association (p value < 0.00001) was reported between co-morbid conditions and death.Conclusion:According to the results of this study, close caution should be exercised in case of patients infected with H1N1 particularly those with co-morbidities.

Epidemiological Characteristics of Influenza in Children during the 2017–2018 and 2018–2019 Influenza Seasons in Jeju, Korea

목적: 제주 지역에서 2017-2018 절기와 2018-2019 절기에 소아 연령에서 인플루엔자의 역학에 대해 알아보고자 하였다. 이에 더하여 국내 인플루엔자 표본감시체계와 비교하여 그 대표성을 확인해보고자 하였다. 방법: 2017-2018, 2018-2019 각각의 절기에 제주대학교 병원에 방문하여 인플루엔자 검사를 시행 받은 13세 미만의 소아를 대상으로 하였다. 의무기록을 통하여 대상 환자들의 인구학적 자료, 인플루엔자 검사 결과를 후향적으로 분석하였다. 결과: 총 5,219명의 인플루엔자 의사환자가 연구 대상자로 포함되었다. 전체적으로 연구 대상자의 평균 나이는 2.85±2.79세였고, 두 절기 모두 인플루엔자 의사환자는 1세 연령 그룹이 가장 많았다. 인플루엔자 감염이 확인된 소아는 총 902 (17.3%)명이었다. 2017-2018 절기에는 인플루엔자 A형의 양성률은 10.4% (236/2,279), 인플루엔자 B형의 양성률은 9.1% (208/2,279)이었다. 2018-2019 절기에는 인플루엔자 A형의 양성률은 10.3% (303/2,940), 인플루엔자 B형의 양성률은 5.3% (155/2,940)이었다. 인플루엔자 환자의 평균 연령은 2017-2018 절기에는 4.09세, 2018-2019 절기에는 5.05세로 통계적으로 유의한 차이를 보였다 (P<0.05). 인플루엔자의 주별 분포는 국내 임상감시시스템의 인플루엔자 의사환자와 유사한 형태로 나타났다. 결론: 제주 지역에서 2017-2018 절기와 2018-2019 절기 사이에 인플루엔자 유행 양상과 연령 분포의 뚜렷한 차이를 보였다. 국내 다른 지역과의 역학적 특성과 비교하여 제주 지역 고유의 인플루엔자 역학에 대한 지속적인 연구가 필요하다.

Clinical and epidemiological characteristics of 245 cases of influenza A (H3N2)

Objective: To investigate the clinical and epidemiological characteristics of influenza A (H3N2) infected patients in Jinhua area, and therefore to improve the understanding of infection with H3N2 influenza virus. Methods: The pharynx swab specimens for pathogenic detection were collected from acute respiratory infection (ARI) cases in the fever clinic of the sentinel hospital in Jinhua area from 2014 to 2017. Descriptive statistics method was used to analyze the clinical features and pathogenics characteristics of the patients infected with H3N2 influenza virus. The t test or χ(2) test of independent samples were used for comparison between groups. Results: A total of 3 803 cases of acute respiratory infection (ARI) were reported in the sentinel hospital in Jinhua area from 2014 to 2017. Among them, 245 cases (6.4%) of H3N2 influenza were diagnosed, including 153 males (62.4%) and 92 females (37.6%), aged from 0.5 to 95 years, with an average age of (50.1+15.7) years. They were divided into 5 age groups, with 107 (43.7%) patients aged 60 years and older. The incidence of major diseases was 43.7%. There was no significant difference in the gender in different age groups (χ(2)=4.581, P=0.333). The seasonal peak of H3N2 influenza A virus infection was mainly in summer (In June-September), but was also seen in other months. In the 4 years from 2014 to 2017, there were a total of 4 peaks, which occurred in July-September, July-August, June-August, and June-August. The body temperature of most patients (73.1%) was between 38.0 and 38.9 ℃. The main positive signs of H3N2 influenza A virus infection were different degrees of pharyngeal hyperemia and tonsillar enlargement. Fever (>38 ℃), cough, dizziness, fatigue, sore throat, headache, chills, shortness of breath, runny nose, myalgia, expectoration, nasal congestion were the main symptoms of H3N2 cases. The proportion of abnormal X-ray/CT manifestations in H3N2 influenza A virus infection cases was lower than that of other influenza viruses. 89.8% of the patients were positive for H3N2 influenza A. The average lymphocyte count was (1.1±0.5) × 10(9)/L, total platelet count (157±39) × 10(9)/L in H3N2 influenza A infection group, which were lower than those in other influenza positive patients [(1.2±0.6)×10(9)/L and (165±42) × 10(9)/L], while the neutrophil count (3.6±0.8) × 10(9)/L was higher than that in other influenza positive patients (3.4±1.0) × 10(9)/L(all P<0.05). Conclusions: Patients with H3N2 influenza A in Jinhua mostly presented with throat congestion and tonsillar enlargement in varying degrees, fever (>38 ℃), cough and sputum production. The seasonal peak of influenza A was in summer (June-September). Elderly aged 60 years or older were the susceptible group.

Epidemiological characteristics of influenza in Guangdong province, during winter of 2017-2018

Objective: To understand the epidemiological characteristics of influenza in Guangdong province, during the winter of 2017-2018, to provide evidence for response to the diversity of influenza, in different seasonal patterns. Methods: Data on weekly influenza surveillance from January 2016 to April 2018, were collected in Guangdong. Information on patients with Influenza-like illness (ILI), on influenza virus positive rates and on outbreaks during the winter of 2017 to 2018, was analyzed and compared with those in spring of 2016 and summer of 2017. χ(2) test and Fisher exact test were used. Results: In the above said winter, the average percentage of visits for ILI in 28 hospitals where sentinel surveillance program had been set, was 4.99% (157 235/3 149 656), which was above the level of the same period in the previous five years. The positive rates of influenza virus among samples collected from ILI outpatients and hospitalized cases under severe acute respiratory infection (SARI) were 28.33% (2 137/7 543) and 14.93% (256/1 715), with the proportions of B (Yamagata) as 70.43% (1 505/2 137) and 73.05% (187/256) respectively. A total of 257 influenza outbreaks were reported in the winter period, with 82.49% (212/257) occurred in elementary schools. Cases aged 6-14 years occurred in winter and spring appeared of having higher positive rate than those seen in summer (P<0.05) whereas elderly cases aged 60 and above showed higher positive rate in summer than those in winter and spring two seasons (P<0.05). Conclusions: Epidemiological characteristics of influenza appeared in Guangdong province, during the winter from 2017 to 2018, were correlated to Influenza B (Yamagata). Capacity on the implementation of surveillance programs and on the coverage of vaccination should be improved and increased in order to control influenza in different epidemic seasons, in Guangzhou.

Клинико-эпидемиологические особенности гриппа у детей Рязанской области в эпидсезоне 2015–2016 гг.

Клинико-эпидемиологические особенности гриппа у детей Рязанской области в эпидсезоне 2015–2016 гг.

THE CLINICAL-EPIDEMIOLOGICAL CHARACTERISTIC OF THE FLU IN KRASNODAR TERRITORY IN 2016

Aim. Clinical and epidemiological characteristics of influenza in the Krasnodar Territory for 2016. Material and methods. The article uses the results of the monitoring of the circulation of influenza viruses from the Federal budgetary establishment of public health services Center for Hygiene and Epidemiology in the Krasnodar Territory in 2016, as well as the clinical features of influenza according to the reports of the Specialized Infectious Diseases Hospital of the Ministry of Health of the Krasnodar Territory for the same period. Results. It was demonstrated that prevalence in the circulation of the influenza strain in the Krasnodar Territory during the year 2016 was A (H1N1) pdm09, the content of which was 96.0%, less frequent influenza A (H3N2) – 2.0% and influenza B – 2.0% . Analysis of the intensity of influenza immunity showed a high percentage of seropositive persons against the influenza B virus (99%), a smaller proportion to the virus A (H3N2) – 40.0% and to the virus A (H1N1) pdm09 – 36%. The hospitalized incidence of influenza and its dynamics are estimated, the characteristics of the clinical course of influenza during the reporting period with details of complications, frequency and causes of deaths are given. Conclusion . The increase in the number of influenza patients who received inpatient treatment in 2016 as compared to 2015, the rarity of erroneous referral diagnoses, prevalence in the structure of patients with moderate disease, complications in the form of community-acquired pneumonia, which determined the death rate 1.1%, was underlined.

Construction of early warning model of influenza-like illness in Zhejiang Province based on support vector machine

To construct a forecasting model of influenza-like illness in Zhejiang Province. The number of influenza-like cases and related pathogens among outpatients and emergency patients were obtained from 11 sentinel hospitals in Zhejiang Province during 2012 to 2013 (total 104 weeks), and corresponding meteorological factors were also collected. The epidemiological characteristics of influenza during the period were then analyzed. Linear correlation and rank correlation analyses were conducted to explore the association between influenza-like illness and related factors. Optimal parameters were selected by cross validation. Support vector machine was used to construct the forecasting model of influenza-like illness in Zhejiang Province and verified by the historical data. Correlation analysis indicated that 8 factors were associated with influenza-like illness occurred in one week. The results of cross validation showed that the optimal parameters were C=3, ε=0.009 and γ=0.4. The results of influenza-like illness forecasting model after verification revealed that support vector machine had the accuracy of 50.0% for prediction with the same level, while it reached 96.7% for prediction within the range of one level higher or lower. Support vector machine is suitable for early warning of influenza-like illness.

Clinico-epidemiological profile of Influenza A H1N1 cases admitted at a tertiary care institute of western India.

Background: H1N1 is a novel strain of Influenza A virus that evolved by genetic reassortment. Following its emergence in March 2009 in Mexico, H1N1 virus spread rapidly throughout the world. India confirmed its first case on 16 May 2009 when someone tested positive for the H1N1 in Hyderabad. Aims & Objectives: (1) To study the epidemiology of Influenza A H1N1 cases; (2) To study clinical presentation of Influenza A H1N1 cases. Materials and Methods: Clinical epidemiological characteristics of Influenza A H1N1 cases admitted at IDW (Infectious Disease Ward) at Government Medical College and Hospital (GMCH), Solapur. Cases from August 2009 to December 2009 were descriptively analysed. Data were analysed using MS Excel software. Results: At GMCH, till December 2009, a total 4229 patients were screened for Influenza A H1N1, of which 110 were admitted and tested. Maximum cases were detected in the month of October and the patients of age group >15-30 years accounted for 30% (33 cases) of the cases. Influenza A H1N1 resulted in death of 17.2% of the admitted cases, of which 47% deaths occurred within 48 h of admission. Common symptoms were fever and cough. Conclusion: On the basis of these findings, it can be safely hypothesized that prevalence of Influenza A H1N1 is high in the younger population, and fever, cough and sore throat are the most common symptoms with which the patients usually present.

Influenza A(H1N1)pdm09-Associated Pneumonia Deaths in Thailand

BackgroundThe first human infections with influenza A(H1N1)pdm09 virus were confirmed in April 2009. We describe the clinical and epidemiological characteristics of influenza A(H1N1)pdm09-associated pneumonia deaths in Thailand from May 2009-January 2010.MethodsWe identified influenza A(H1N1)pdm09-associated pneumonia deaths from a national influenza surveillance system and performed detailed reviews of a subset.ResultsOf 198 deaths reported, 49% were male and the median age was 37 years; 146 (73%) were 20–60 years. Among 90 deaths with records available for review, 46% had no identified risk factors for severe influenza. Eighty-eight patients (98%) received antiviral treatment, but only 16 (18%) initiated therapy within 48 hours of symptom onset.ConclusionsMost influenza A(H1N1)pdm09 pneumonia fatalities in Thailand occurred in adults aged 20–60 years. Nearly half lacked high-risk conditions. Antiviral treatment recommendations may be especially important early in a pandemic before vaccine is available. Treatment should be considered as soon as influenza is suspected.

Descriptive clinical and epidemiological characteristics of influenza A H1N1 2009 virus infections in pigs in England

Infection of pigs with influenza A H1N1 2009 virus (A(H1N1)pdm09) was first detected in England in November 2009 following global spread of the virus in the human population. This paper...

Clinical-Epidemiological Profile of Influenza A H1N1 Cases at a Tertiary Care Institute of India

Introduction:Influenza virus is a common human pathogen that has caused serious respiratory illness and death over the past century. In April 2009, a new strain of Influenza virus A H1N1, commonly referred to as “swine flu”, began to spread in several countries around the world, and India confirmed its first case on 16 May 16 2009.Aim:To study the clinical and epidemiological profile of Influenza A H1N1 cases at the Government Medical College and Hospital, Chandigarh.Materials and Methods:Clinical epidemiological characteristics of Influenza A H1N1 cases from May 2009 to April 2010 were retrospectively, descriptively analyzed using data from the Influenza A H1N1 screening center and isolation ward at the Government Medical College and Hospital, Chandigarh. Data were Analyzed using MS Excel software.Results:At GMCH, till April 2010, a total of 4379 patients were screened for Influenza A H1N1, of which 365 patients were tested. The most common symptoms were fever (87.6%), cough (49.77%), sore throat (27%) and breathlessness (23.9%). The most common presentation (42.30%) of Influenza A H1N1 cases was fever and cold-like features, not cough. 29.58% (108) of the tested patients were found to be positive for the disease. Maximum cases were detected in the month of December, and the patients less than 40 years of age accounted for 81.4% (44 cases) of the cases. Influenza A H1N1 resulted in death of 54.9% (28) of the admitted cases, of which 46% (12) deaths occurred within 48 h of admission.Conclusion:On the basis of these findings, it can be safely hypothesized that prevalence of Influenza A H1N1 is high in the younger population, and fever, cough and sore throat are the most common symptoms with which the patients usually present.

Monitoring of Influenza Viruses in the Aftermath of the Great East Japan Earthquake

Influenza has a significant impact on public health when a natural disaster occurs during the influenza season. However, the epidemiological characteristics of influenza following natural disasters have not been well documented due to the difficulty of implementing laboratory-based influenza surveillance in such situations. The Great East Japan Earthquake occurred on March 11, 2011, when influenza was already circulating. Since routine influenza surveillance was not performed in Miyagi Prefecture, we initiated an ad hoc laboratory-based monitoring system immediately after the earthquake. From March 15 to May 19, we tested 277 samples for influenza virus collected around Sendai City and from evacuation centers in Miyagi Prefecture. Influenza A (H3N2) was detected in 112 cases, influenza A (H1N1) 2009 in one case, and influenza B in 92 cases. The H3N2 virus was dominant until the 14th week. However, a sudden increase in the number of influenza B cases occurred after schools were reopened. According to phylogenetic analysis, a major clade switch of the H3N2 virus took place after the earthquake. The Yamagata lineage of influenza B was detected in one patient from western Japan, indicating the importing of viruses into the affected area.

Epidemiological characteristics of influenza A(H1N1) 2009 pandemic in the Western Pacific Region

The first laboratory-confirmed cases of infection with pandemic influenza A(H1N1) 2009 in the Western Pacific Region were reported on 28 April 2009. By 11 June 2009, the day the pandemic was declared by the World Health Organization, nine Western Pacific Region countries and areas had reported laboratory confirmed pandemic influenza A(H1N1) 2009 cases. From April 2009 to July 2010, more than 250000 cases and 1800 deaths from laboratory-confirmed pandemic influenza A(H1N1) 2009 were reported from 34 countries and areas in the Region. By age group region-wide, 8.6%, 41.9%, 48.3%, and 1.2% of cases were in the <5years, 5-14 years, 15-64 years, and 65+ years age groups, respectively; the overall crude case fatality ratio in the Western Pacific Region was 0.5%. The pandemic demonstrated that region-wide disease reporting was possible. Countries and areas of the Western Pacific Region should take this opportunity to strengthen the systems established during the pandemic to develop routine disease reporting.

Demographic and epidemiological characteristics of influenza in HIMA, San Pablo Caguas Hospital, Puerto Rico

Demographic and epidemiological characteristics of influenza in HIMA, San Pablo Caguas Hospital, Puerto Rico