Influenza-associated Influenza-like Illness Research Articles

Cost-effectiveness analysis of quadrivalent influenza vaccination for older adults aged 60 and above in mainland China

Objective: To evaluate the cost-effectiveness of government fully-funded quadrivalent influenza vaccination (QIV) program for older adults aged 60 and above in mainland China. Methods: Based on decision tree model in the previous research on the cost-effectiveness analysis of TIV immunization, we extended the structure of model and updated the key parameters such as influenza patients' healthcare seeking behavior, vaccine cost, vaccine coverage and vaccine efficacy/effectiveness to estimate influenza-associated outpatient consultations, hospitalizations, respiratory disease excess mortality and quality-adjusted life years (QALY) between the QIV and no vaccination or TIV program. And incremental cost and incremental cost-effectiveness ratio (ICER) were evaluated between the QIV and no vaccination or TIV program from the societal perspective. The time frame of the study is one year. All costs were adjusted to 2019 using the consumer price index. Results: Comparing the fully-funded QIV and no vaccination or TIV for older adults aged 60 and above is separately expected to prevent 45 070 or 2 718 influenza-associated influenza-like illness (ILI) outpatients, 21 451 or 1 294 influenza-associated severe acute respiratory infection (SARI) hospitalizations, 19 346 or 1 167 influenza-associated respiratory excess deaths and avoid 155 234 or 9 363 QALY loss each year. Compared with no vaccination, introducing QIV into National Immunization Program (NIP) is expected to increase the cost of 11.71 billion yuan from the societal perspective. The incremental cost per QALY gained between QIV and no vaccination was 75 325 yuan per QALY, which is higher than willingness-to-pay (WTP) threshold (one-fold gross domestic product per capita is considered as WTP: 70 892 yuan) and means no cost effective. Introducing QIV rather than TIV into NIP will cost 7.98 billion yuan from the societal perspective and the ICER was 852.54 thousand yuan per QALY which is much higher than WTP and means no cost effective as well. The threshold of vaccination cost between QIV and no vaccination or TIV should no more than 113.41 or 6.83 yuan when the two comparators' scenarios above are all cost effective. Conclusion: Under the condition of current vaccine effectiveness and vaccine cost, comparing fully-funded QIV with no or TIV vaccination program is not cost effective for people aged 60 years or older.

Influenza epidemiology and burden of disease in Mongolia, 2013–2014 to 2017–2018

Background: Mongolia is a vast, sparsely populated country in central Asia. Its harsh climate and nomadic lifestyle make the population vulnerable to acute respiratory infections, particularly influenza. Evidence on the morbidity, mortality and socioeconomic impact of influenza in Mongolia is scarce; however, routine surveillance for influenza-like illness (ILI), severe acute respiratory infection (SARI) and laboratory-detected influenza is conducted. This paper describes the epidemiology of influenza and the estimated burden of influenza-associated illness in Mongolia in the five influenza seasons between 2013–2014 and 2017–2018. Methods: Demographic and laboratory data from 152 sentinel surveillance sites on all patients who met the case definitions of ILI and SARI between October 2013 and May 2018 were extracted and analysed as described in A Manual for Estimating Disease Burden Associated with Seasonal Influenza. Results: The estimated annual influenza-associated ILI and SARI rates, presented as ranges, were 1279–2798 and 81–666 cases per 100 000 population, respectively. Children aged <5 years accounted for 67% of all ILI cases and 79% of all SARI cases. The annual specimen positivity for influenza was highest (11–30% for ILI and 8–31% for SARI) for children aged 5–<15 years and children <2 years old, respectively. The annual mortality rate due to pneumonia and SARI was highest among children aged <2 years (15.8–54.0 per 100 000 population). Although the incidence of influenza-associated ILI and SARI was lowest for people aged >65 years, the mortality rate due to pneumonia and SARI (1.2–5.1 per 100 000) was higher than that for those aged 15–64 years. Conclusion: The estimated influenza-associated ILI and SARI incidence rates are high in Mongolia, and children, especially those aged <5 years, have the highest influenza-associated burden in Mongolia. These findings provide evidence for decision-makers in Mongolia to consider targeted influenza vaccination, particularly for children.

Study on clinical symptoms and influencing factors of influenza-associated severe acute respiratory illness in children younger than 5 years old in Suzhou of China, 2011-2017

Objective: To study the influencing factors of influenza-associated severe acute respiratory illness (SARI) in children younger than 5 years of old in Suzhou, and to provide evidence to support the improvement of prevention and control strategies for influenza in children. Methods: We conducted a prospective influenza surveillance for hospitalized SARI and outpatient influenza-like illness (ILI) at Children's Hospital of Soochow University from April 2011 to March 2017. We compared the clinical and other characteristics of influenza-positive patients with SARI to those with ILI to find the differences and to identify influencing factors of influenza-associated SARI, using χ2 test and unconditional logistic regression. Results: We found 786 cases of influenza-associated ILI and 413 cases of influenza-associated SARI during the study period. Cough, runny nose, shortness of breath, asthma or wheezing were more common in influenza-associated SARI than in influenza-associated ILI (P<0.01). Univariate and multivariate logistic regression showed that the influencing factors which significantly associated with increased risk of influenza-associated SARI were as follows: younger age (<6 months OR=3.6, 6-23 months aOR=2.5), respiratory infection history within 3 months (aOR=4.5), chronic lung disease history (OR=3.4), fever above 39.0 ℃ (39.0-39.9 ℃ aOR=2.4, ≥40.0 ℃ aOR=6.0), and the presence of A/H1N1 (aOR=2.3), A/H3N2 (aOR=1.9). Conclusion: Children younger than 2 years old, with a history of chronic lung disease, a history of respiratory infection within 3 months, or with a fever peak above 39.0 ℃ should seek medical advice as soon as possible or receive annual influenza vaccination to reduce the incidence of influenza-associated serious outcomes.

Influenza epidemiology and burden of disease in Mongolia, 2013-2014 to 2017-2018.

BackgroundMongolia is a vast, sparsely populated country in central Asia. Its harsh climate and nomadic lifestyle make the population vulnerable to acute respiratory infections, particularly influenza. Evidence on the morbidity, mortality and socioeconomic impact of influenza in Mongolia is scarce; however, routine surveillance for influenza-like illness (ILI), severe acute respiratory infection (SARI) and laboratory-detected influenza is conducted. This paper describes the epidemiology of influenza and the estimated burden of influenza-associated illness in Mongolia in the five influenza seasons between 2013–2014 and 2017–2018.MethodsDemographic and laboratory data from 152 sentinel surveillance sites on all patients who met the case definitions of ILI and SARI between October 2013 and May 2018 were extracted and analysed as described in A Manual for Estimating Disease Burden Associated with Seasonal Influenza.ResultsThe estimated annual influenza-associated ILI and SARI rates, presented as ranges, were 1279–2798 and 81–666 cases per 100 000 population, respectively. Children aged < 5 years accounted for 67% of all ILI cases and 79% of all SARI cases. The annual specimen positivity for influenza was highest (11–30% for ILI and 8–31% for SARI) for children aged 5– < 15 years and children < 2 years old, respectively. The annual mortality rate due to pneumonia and SARI was highest among children aged < 2 years (15.8–54.0 per 100 000 population). Although the incidence of influenza-associated ILI and SARI was lowest for people aged 365 years, the mortality rate due to pneumonia and SARI (1.2–5.1 per 100 000) was higher than that for those aged 15–64 years.ConclusionThe estimated influenza-associated ILI and SARI incidence rates are high in Mongolia, and children, especially those aged < 5 years, have the highest influenza-associated burden in Mongolia. These findings provide evidence for decision-makers in Mongolia to consider targeted influenza vaccination, particularly for children.

Estimating the disease burden of seasonal influenza in China, 2006-2019

Objective: To estimate the health impact and economic burden of seasonal influenza in mainland China. Methods: From systematic literature reviews, we collected the influenza-associated excess influenza-like-illness (ILI) outpatient consultation rates, hospitalization rates of severe acute respiratory infections (SARI) and respiratory excess mortality, 2006-2017. Using these data, as well as demographic data (2019), the number of influenza-associated excess ILI outpatient consultations, SARI hospitalizations and respiratory excess deaths were estimated. Then using per capita economic burden of influenza-associated outpatient consultations and hospitalizations, as well as the productivity loss of influenza-related premature deaths, the annual influenza-associated total economic burden was estimated. All costs were adjusted to 2019 using the consumer price index. Results: The annual influenza-associated excess ILI outpatient consultations, SARI hospitalizations and excess respiratory deaths were 3 million, 2.34 million, 0.09 million, respectively. The total economic burden was 26.38 billion CNY, accounting for 0.266‰ GDP in 2019, of which the hospitalization-related economic burden accounted for the highest proportion (86.4%, 22.79 billion CNY), followed by the outpatient-related economic burden (11.3%, 2.97 billion CNY), and the indirect economic burden of productivity loss of premature deaths was the lowest (2.4%, 0.62 billion CNY). Largest economic burden was observed in East China (10.51 billion CNY) and smallest observed in Northeast China (0.38 billion CNY). Conclusion: The health burden of influenza-related outpatient visits and hospitalizations were substantial. The economic burden of influenza-related SARI hospitalization was higher than that of influenza-related outpatients and pre-mature deaths. The highest economic burden of influenza occurred in the East China.

Effectiveness of influenza vaccine among health care personnel in Thailand, 2018/19 season

Abstract Background Influenza vaccination is the most effective way of preventing influenza infections and it is recommended for the entire health care personnel in Thailand. However, the evidence of influenza vaccine effectiveness (VE) among health care personnel is lacking in Thailand. The objective of this study was to estimate influenza vaccine effectiveness (VE) against laboratory confirmed medically attended influenza illness for the 2018/9 season among health care personnel who at risk for influenza infection in Bangkok, the capital of Thailand. Methods Throat swab specimens were collected from patients with influenza-like illness (ILI) presenting to outpatient clinics and tested for influenza virus by RT-PCR, between October 2018 and September 2019. A test-negative case-control design was used to estimate influenza VE against medically-attended laboratory-confirmed influenza in outpatient settings. Cases were influenza-like illness (ILI) patients who tested positive for influenza, and controls were influenza negative patients. Results During the 2018/19 season 373 samples were collected; 57 (15.3%) were positive for influenza, 70.2% A un-subtyped and 29.8% B. Adjusted VE against all influenza viruses for this influenza season was -31.7% (95% confidence interval (CI): -40.2 to 66.4), against influenza A un-subtyped, it was 43.9% (95% CI: -30.6 to 75.9) and against influenza B, it was 52.0% (95% CI: (-73.9 to 86.8). Conclusions The seasonal influenza vaccine was moderately effective against medically attended lab-confirmed influenza infection in health care personnel in Bangkok, Thailand in the 2018-19 influenza season. Key messages The seasonal influenza vaccine was moderately effective against medically attended lab-confirmed influenza infection in health care personnel in Bangkok. Increasing seasonal influenza vaccination among health care personnel in Thailand may decrease medically attended influenza-associated ILI cases in this population.

Burden of influenza-associated outpatient influenza-like illness consultations in China, 2006-2015: A population-based study.

BackgroundHuman influenza virus infections cause a considerable burden of morbidity and mortality worldwide each year. Understanding regional influenza‐associated outpatient burden is crucial for formulating control strategies against influenza viruses.MethodsWe extracted the national sentinel surveillance data on outpatient visits due to influenza‐like‐illness (ILI) and virological confirmation of sentinel specimens from 30 provinces of China from 2006 to 2015. Generalized additive regression models were fitted to estimate influenza‐associated excess ILI outpatient burden for each individual province, accounting for seasonal baselines and meteorological factors.ResultsInfluenza was associated with an average of 2.5 excess ILI consultations per 1000 person‐years (py) in 30 provinces of China each year from 2006 to 2015. Influenza A(H1N1)pdm09 led to a higher number of influenza‐associated ILI consultations in 2009 across all provinces compared with other years. The excess ILI burden was 4.5 per 1000 py among children aged below 15 years old, substantially higher than that in adults.ConclusionsHuman influenza viruses caused considerable impact on population morbidity, with a consequent healthcare and economic burden. This study provided the evidence for planning of vaccination programs in China and a framework to estimate burden of influenza‐associated outpatient consultations.

Estimation of the burden of flu-association influenza-like illness visits on total clinic visits through the sentinel influenza monitoring system in Senegal during the 2013-2015 influenza seasons.

Knowing the burden of influenza is helpful for policy decisions. Here we estimated the contribution of influenza-like illness (ILI) visits associated with laboratory-confirmed influenza among all clinic visits in a Senegal sentinel network. ILI data from ten sentinel sites were collected from January 2013 to December 2015. ILI was defined as an axillary measured fever of more than 37.5 °C with a cough or a sore throat. Collected nasopharyngeal swabs were tested for influenza viruses by rRT-PCR. Influenza-associated ILI was defined as ILI with laboratory-confirmed influenza. For the influenza disease burden estimation, we used all-case outpatient visits during the study period who sought care at selected sites. Of 4030 ILI outpatients tested, 1022 were influenza positive. The estimated proportional contribution of influenza-associated ILI was, per 100 outpatients, 1.2 (95% CI 1.1-1.3), 0.32 (95% CI 0.28-0.35), 1.11 (95% CI 1.05-1.16) during 2013, 2014, 2015, respectively. The age-specific outpatient visits proportions of influenza-associated ILI were higher among children under 5 years (0.68%, 95% CI: 0.62-0.70). The predominant virus during years 2013 and 2015 was influenza B while A/H3N2 subtype was predominant during 2014. Influenza viruses cause a substantial burden of outpatient visits particularly among children under 5 of age in Senegal and highlight the need of vaccination in risk groups.

Estimation of community-level influenza-associated illness in a low resource rural setting in India.

ObjectiveTo estimate rates of community-level influenza-like-illness (ILI) and influenza-associated ILI in rural north India.MethodsDuring 2011, we conducted household-based healthcare utilization surveys (HUS) for any acute medical illness (AMI) in preceding 14days among residents of 28villages of Ballabgarh, in north India. Concurrently, we conducted clinic-based surveillance (CBS) in the area for AMI episodes with illness onset ≤3days and collected nasal and throat swabs for influenza virus testing using real-time polymerase chain reaction. Retrospectively, we applied ILI case definition (measured/reported fever and cough) to HUS and CBS data. We attributed 14days of risk-time per person surveyed in HUS and estimated community ILI rate by dividing the number of ILI cases in HUS by total risk-time. We used CBS data on influenza positivity and applied it to HUS-based community ILI rates by age, month, and clinic type, to estimate the community influenza-associated ILI rates.FindingsThe HUS of 69,369 residents during the year generated risk-time of 3945 person-years (p-y) and identified 150 (5%, 95%CI: 4–6) ILI episodes (38 ILI episodes/1,000 p-y; 95% CI 32–44). Among 1,372 ILI cases enrolled from clinics, 126 (9%; 95% CI 8–11) had laboratory-confirmed influenza (A (H3N2) = 72; B = 54). After adjusting for age, month, and clinic type, overall influenza-associated ILI rate was 4.8/1,000 p-y; rates were highest among children <5 years (13; 95% CI: 4–29) and persons≥60 years (11; 95%CI: 2–30).ConclusionWe present a novel way to use HUS and CBS data to generate estimates of community burden of influenza. Although the confidence intervals overlapped considerably, higher point estimates for burden among young children and older adults shows the utility for exploring the value of influenza vaccination among target groups.

The effects of the attributable fraction and the duration of symptoms on burden estimates of influenza-associated respiratory illnesses in a high HIV prevalence setting, South Africa, 2013-2015.

BackgroundThe attributable fraction of influenza virus detection to illness (INF‐AF) and the duration of symptoms as a surveillance inclusion criterion could potentially have substantial effects on influenza disease burden estimates.MethodsWe estimated rates of influenza‐associated influenza‐like illness (ILI) and severe acute (SARI‐10) or chronic (SCRI‐10) respiratory illness (using a symptom duration cutoff of ≤10 days) among HIV‐infected and HIV‐uninfected patients attending 3 hospitals and 2 affiliated clinics in South Africa during 2013‐2015. We calculated the unadjusted and INF‐AF‐adjusted rates and relative risk (RR) due to HIV infection. Rates were expressed per 100 000 population.ResultsThe estimated mean annual unadjusted rates of influenza‐associated illness were 1467.7, 50.3, and 27.4 among patients with ILI, SARI‐10, and SCRI‐10, respectively. After adjusting for the INF‐AF, the percent reduction in the estimated rates was 8.9% (rate: 1336.9), 11.0% (rate: 44.8), and 16.3% (rate: 22.9) among patients with ILI, SARI‐10, and SCRI‐10, respectively. HIV‐infected compared to HIV‐uninfected individuals experienced a 2.3 (95% CI: 2.2‐2.4)‐, 9.7 (95% CI: 8.0‐11.8)‐, and 10.0 (95% CI: 7.9‐12.7)‐fold increased risk of influenza‐associated illness among patients with ILI, SARI‐10, and SCRI‐10, respectively. Overall 34% of the estimated influenza‐associated hospitalizations had symptom duration of >10 days; 8% and 44% among individuals aged <5 and ≥5 years, respectively.ConclusionThe marginal differences between unadjusted and INF‐AF‐adjusted rates are unlikely to affect policies on prioritization of interventions. HIV‐infected individuals experienced an increased risk of influenza‐associated illness and may benefit more from annual influenza immunization. The use of a symptom duration cutoff of ≤10 days may underestimate influenza‐associated disease burden, especially in older individuals.

Influenza activity in Tunisia: 2014-2015 season

Introduction : Influenza is an important public health problem; it is a major cause of morbidity and leads to considerable socio-economic consequences. The aim of this study was to assess influenza activity for the 2014-2015 season in Tunisia. Methods : Influenza surveillance data was used for data analysis. It was obtained from National Program for Surveillance and Control of influenza which involves the National Influenza Centre (NIC) as well as a network of 268 sentinel sites for reporting influenza-like illness (ILI). The NIC receives biological specimen from the ILI sentinel sites as well as from university hospitals. The case definition of ILI was that recommended by WHO “acute respiratory illness, and measured fever ≥ 38°C, and cough, and onset in previous 10 days”. Results : Influenza activity was relatively moderate at the national level during the 2014-15 season. It differed significantly according to age (p Conclusion : The 2014-2015 influenza season was marked by a moderate disease burden of influenza-associated ILI and a co-circulation of three influenza viruses. Reliable surveillance data is needed to provide decision-makers with the evidence necessary for public health policies on influenza prevention and control. Determining influenza viruses in circulation ensures the adequacythe vaccine and eventually detection of new influenza viruses with pandemic potential.

Estimating burden of influenza-associated influenza-like illness and severe acute respiratory infection at public healthcare facilities in Romania during the 2011/12-2015/16 influenza seasons.

BackgroundInfluenza is responsible for substantial morbidity and mortality, but there is limited information on reliable disease burden estimates, especially from middle‐income countries in the WHO European Region.ObjectivesTo estimate the incidence of medically attended influenza‐associated influenza‐like illness (ILI) and hospitalizations due to severe acute respiratory infection (SARI) presenting to public healthcare facilities in Romania.Patients/MethodsSentinel influenza surveillance data for ILI and SARI from 2011/12‐2015/16, including virological data, were used to estimate influenza‐associated ILI and SARI incidence/100 000 and their 95% confidence intervals (95% CI).ResultsThe overall annual incidence of ILI and influenza‐associated ILI per 100 000 persons in Romania varied between 68 (95% CI: 61‐76) and 318 (95% CI: 298‐338) and between 23 (95% CI: 19‐29) and 189 (95% CI: 149‐240), respectively. The highest ILI and influenza incidence was among children aged 0‐4 years. We estimated that SARI incidence per 100 000 persons was 6 (95% CI: 5‐7) to 9 (95% CI: 8‐10), of which 2 (95% CI: 1‐2) to 3 (95% CI: 2‐4) were due to influenza. Up to 0.3% of the Romanian population were annually reported with ILI, and 0.01% was hospitalized with SARI, of which as much as one‐third could be explained by influenza.ConclusionsThis evaluation was the first study estimating influenza burden in Romania. We found that during each influenza season, a substantial number of persons in Romania suffer from influenza‐related ILI or are hospitalized due to influenza‐associated SARI.

Incidence of medically attended influenza among residents of Shai-Osudoku and Ningo-Prampram Districts, Ghana, May 2013 - April 2015.

BackgroundInfluenza vaccination is recommended by the World Health Organization for high risk groups, yet few data exist on influenza disease burden in West Africa.MethodsWe estimated medically attended influenza-associated illness rates among residents of Shai-Osudoku and Ningo Pram-Pram Districts (SONPD), Ghana. From May 2013 to April 2015, we conducted prospective surveillance for severe acute respiratory illness (SARI) and influenza-like illness (ILI) in 17 health facilities. In 2015, we conducted a retrospective assessment at an additional 18 health facilities to capture all SONPD SARI and ILI patients during the study period. We applied positivity rates to those not tested to estimate total influenza cases.ResultsOf 612 SARI patients tested, 58 (9%) were positive for influenza. The estimated incidence of influenza-associated SARI was 30 per 100,000 persons (95% CI: 13-84). Children aged 0 to 4 years had the highest influenza-associated SARI incidence (135 per 100,000 persons, 95% CI: 120-152) and adults aged 25 to 44 years had the lowest (3 per 100,000 persons, 95% CI: 1-7) (p < 0.01). Of 2,322 ILI patients tested, 407 (18%) were positive for influenza. The estimated incidence of influenza-associated ILI was 844 per 100,000 persons (95% CI: 501-1,099). The highest incidence of influenza-associated ILI was also among children aged 0 to 4 years (3,448 per 100,000 persons, 95% CI: 3,727 – 3,898). The predominant circulating subtype during May to December 2013 and January to April 2015 was influenza A(H3N2) virus, and during 2014 influenza B virus was the predominant circulating type.ConclusionsInfluenza accounted for 9% and 18% of medically attended SARI and ILI, respectively. Rates were substantive among young children and suggest the potential value of exploring the benefits of influenza vaccination in Ghana, particularly in this age group.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-2078-x) contains supplementary material, which is available to authorized users.

Modelling of seasonal influenza and estimation of the burden in Tunisia

The burden of influenza was estimated from surveillance data in Tunisia using epidemiological parameters of transmission with WHO classical tools and mathematical modelling. The incidence rates of influenza-associated influenza-like illness (ILI) per 100 000 were 18 735 in 2012/2013 season; 5536 in 2013/14 and 12 602 in 2014/15. The estimated proportions of influenza-associated ILI in the total outpatient load were 3.16%; 0.86% and 1.98% in the 3 seasons respectively. Distribution of influenza viruses among positive patients was: A(H3N2) 15.5%; A(H1N1)pdm2009 39.2%; and B virus 45.3% in 2014/2015 season. From the estimated numbers of symptomatic cases, we estimated that the critical proportions of the population that should be vaccinated were 15%, 4% and 10% respectively. Running the model for the different values of R0, we quantified the number of symptomatic clinical cases, the clinical attack rates, the symptomatic clinical attack rates and the number of deaths. More realistic versions of this model and improved estimates of parameters from surveillance data will strengthen the estimation of the burden of influenza.

Seasonal influenza vaccine effectiveness against medically attended influenza illness among children aged 6–59 months, October 2011–September 2012: A matched test-negative case–control study in Suzhou, China

BackgroundSeasonal influenza infections among young children in China lead to substantial numbers of hospitalizations and financial burden. This study assessed the seasonal influenza vaccine effectiveness (VE) against laboratory confirmed medically attended influenza illness among children in Suzhou, China, from October 2011–September 2012. MethodsWe conducted a test-negative case–control study among children aged 6–59 months who sought care at Soochow University Affiliated Children's Hospital (SCH) from October 2011–September 2012. A case was defined as a child with influenza-like illness (ILI) or severe acute respiratory infection (SARI) with an influenza-positive nasopharyngeal swab by rRT-PCR. Controls were selected from children presenting with ILI or SARI without laboratory confirmed influenza. We conducted 1:1 matching by age and admission date. Vaccination status was verified from the citywide immunization system database. VE was calculated with conditional logistic regression: (1−OR)×100%. ResultDuring the study period, 2634 children aged 6–59 months presented to SCH with ILI (1975) or SARI (659) and were tested for influenza. The vaccination records were available for 69% (1829; ILI: 1354, SARI: 475). Among those, 23% (427) tested positive for influenza, and were included as cases. Among influenza positive cases, the vaccination rates were 3.2% for SARI and 4.5% for ILI. Among controls, the vaccination rates were 13% for SARI, and 11% for ILI. The overall VE against lab-confirmed medically attended influenza virus infection was 67% (95% CI: 41–82). The VE for SARI was 75% (95% CI: 11–93) and for ILI was 64% (95% CI: 31–82). ConclusionsThe seasonal influenza vaccine was effective against medically attended lab-confirmed influenza infection in children aged 6–59 months in Suzhou, China in the 2011–12 influenza season. Increasing seasonal influenza vaccination among young children in Suzhou may decrease medically attended influenza-associated ILI and SARI cases in this population.

Associations between Meteorological Parameters and Influenza Activity in Berlin (Germany), Ljubljana (Slovenia), Castile and León (Spain) and Israeli Districts.

BackgroundStudies in the literature have indicated that the timing of seasonal influenza epidemic varies across latitude, suggesting the involvement of meteorological and environmental conditions in the transmission of influenza. In this study, we investigated the link between meteorological parameters and influenza activity in 9 sub-national areas with temperate and subtropical climates: Berlin (Germany), Ljubljana (Slovenia), Castile and León (Spain) and all 6 districts in Israel.MethodsWe estimated weekly influenza-associated influenza-like-illness (ILI) or Acute Respiratory Infection (ARI) incidence to represent influenza activity using data from each country’s sentinel surveillance during 2000–2011 (Spain) and 2006–2011 (all others). Meteorological data was obtained from ground stations, satellite and assimilated data. Two generalized additive models (GAM) were developed, with one using specific humidity as a covariate and another using minimum temperature. Precipitation and solar radiation were included as additional covariates in both models. The models were adjusted for previous weeks’ influenza activity, and were trained separately for each study location.ResultsInfluenza activity was inversely associated (p<0.05) with specific humidity in all locations. Minimum temperature was inversely associated with influenza in all 3 temperate locations, but not in all subtropical locations. Inverse associations between influenza and solar radiation were found in most locations. Associations with precipitation were location-dependent and inconclusive. We used the models to estimate influenza activity a week ahead for the 2010/2011 period which was not used in training the models. With exception of Ljubljana and Israel’s Haifa District, the models could closely follow the observed data especially during the start and the end of epidemic period. In these locations, correlation coefficients between the observed and estimated ranged between 0.55 to 0.91and the model-estimated influenza peaks were within 3 weeks from the observations.ConclusionOur study demonstrated the significant link between specific humidity and influenza activity across temperate and subtropical climates, and that inclusion of meteorological parameters in the surveillance system may further our understanding of influenza transmission patterns.

The burden of influenza and RSV among inpatients and outpatients in rural western Kenya, 2009-2012.

BackgroundIn Kenya, detailed data on the age-specific burden of influenza and RSV are essential to inform use of limited vaccination and treatment resources.MethodsWe analyzed surveillance data from August 2009 to July 2012 for hospitalized severe acute respiratory illness (SARI) and outpatient influenza-like illness (ILI) at two health facilities in western Kenya to estimate the burden of influenza and respiratory syncytial virus (RSV). Incidence rates were estimated by dividing the number of cases with laboratory-confirmed virus infections by the mid-year population. Rates were adjusted for healthcare-seeking behavior, and to account for patients who met the SARI/ILI case definitions but were not tested.ResultsThe average annual incidence of influenza-associated SARI hospitalization per 1,000 persons was 2.7 (95% CI 1.8–3.9) among children <5 years and 0.3 (95% CI 0.2–0.4) among persons ≥5 years; for RSV-associated SARI hospitalization, it was 5.2 (95% CI 4.0–6.8) among children <5 years and 0.1 (95% CI 0.0–0.2) among persons ≥5 years. The incidence of influenza-associated medically-attended ILI per 1,000 was 24.0 (95% CI 16.6–34.7) among children <5 years and 3.8 (95% CI 2.6–5.7) among persons ≥5 years. The incidence of RSV-associated medically-attended ILI was 24.6 (95% CI 17.0–35.4) among children <5 years and 0.8 (95% CI 0.3–1.9) among persons ≥5 years.ConclusionsInfluenza and RSV both exact an important burden in children. This highlights the possible value of influenza vaccines, and future RSV vaccines, for Kenyan children.

Results from the first six years of national sentinel surveillance for influenza in Kenya, July 2007-June 2013.

BackgroundRecent studies have shown that influenza is associated with significant disease burden in many countries in the tropics, but until recently national surveillance for influenza was not conducted in most countries in Africa.MethodsIn 2007, the Kenyan Ministry of Health with technical support from the CDC-Kenya established a national sentinel surveillance system for influenza. At 11 hospitals, for every hospitalized patient with severe acute respiratory illness (SARI), and for the first three outpatients with influenza-like illness (ILI) per day, we collected both nasopharyngeal and oropharyngeal swabs. Beginning in 2008, we conducted in-hospital follow-up for SARI patients to determine outcome. Specimens were tested by real time RT-PCR for influenza A and B. Influenza A-positive specimens were subtyped for H1, H3, H5, and (beginning in May 2009) A(H1N1)pdm09.ResultsFrom July 1, 2007 through June 30, 2013, we collected specimens from 24,762 SARI and 14,013 ILI patients. For SARI and ILI case-patients, the median ages were 12 months and 16 months, respectively, and 44% and 47% were female. In all, 2,378 (9.6%) SARI cases and 2,041 (14.6%) ILI cases were positive for influenza viruses. Most influenza-associated SARI cases (58.6%) were in children <2 years old. Of all influenza-positive specimens, 78% were influenza A, 21% were influenza B, and 1% were influenza A/B coinfections. Influenza circulated in every month. In four of the six years influenza activity peaked during July–November. Of 9,419 SARI patients, 2.7% died; the median length of hospitalization was 4 days.ConclusionsDuring six years of surveillance in Kenya, influenza was associated with nearly 10 percent of hospitalized SARI cases and one-sixth of outpatient ILI cases. Most influenza-associated SARI and ILI cases were in children <2 years old; interventions to reduce the burden of influenza, such as vaccine, could consider young children as a priority group.

Virological Surveillance of Influenza-Like Illness Among Children in Ghana, 2008–2010

The global annual attack rate for influenza is estimated to be 10%-20% in children, although limited information exists for Africa. In 2007, Ghana initiated influenza surveillance by routine monitoring of acute respiratory illness to obtain data on circulating strains. We describe influenza surveillance in children <11 years old who had influenza-like illness (ILI) from January 2008 to December 2010. Oropharyngeal swabs from pediatric outpatients with ILI attending any of 22 health facilities across the country were submitted. We tested swabs for influenza virus using molecular assays, virus isolation, and hemagglutination assays. Of the 2810 swabs, 636 (23%) were positive for influenza virus. The percentage of positives by gender was similar. The proportion of ILI cases positive for influenza increased with age from 11% (31/275) in infants (aged 0-1 years) to 31% (377/1219) among children aged 5-10 years (P < .001). The majority of cases were influenza A (90%), of which 60% were influenza A(H1N1)pdm09. In all 3 years, influenza activity appeared slightly higher during May through July. During the 3 years of influenza surveillance in Ghana, children aged <11 years bore a high burden of influenza-associated ILI.

Influenza-Like Illness Among University Students: Symptom Severity and Duration Due to Influenza Virus Infection Compared to Other Etiologies

Objective: University students with influenza-like illness (ILI) were assessed to determine whether symptom severity, duration, or missed days of school or work varied according to etiology. Participants: Sixty persons presenting to a university health clinic with ILI symptoms during 3 consecutive influenza seasons completed baseline survey and viral testing; 51 (85%) completed follow-up. Methods: Influenza viral culture and polymerase chain reaction and respiratory virus immunofluorescence assay testing were performed. Information collected at baseline and follow-up included symptom occurrence, severity, duration, and numbers of days of work and school missed. Results: Influenza virus was confirmed in 63% of participants. Influenza-positive individuals were no more likely to report any symptom or miss more days of school or work. Self-reported severity and durations of symptoms were similar between groups. Conclusions: Students with influenza-associated ILI were similar to those with noninfluenza ILI with respect to severity, duration, and numbers of days of school and work missed.