Incidence of influenza-associated hospitalization in rural communities in western and northern India, 2010-2012: a multi-site population-based study

Respiratory viruses associated with severe acute respiratory infection in children aged <5 years at a tertiary care hospital in Delhi, India during 2013-15

Background

With the increased availability of licensed vaccines for respiratory viruses such as severe acute respiratory syndrome coronavirus 2, respiratory syncytial virus (RSV), and influenza virus, a better understanding of the viral aetiology of severe acute respiratory infections (SARI) among children could help in optimising the use of these vaccines. We conducted a study among children aged <5 years hospitalised with SARI at a tertiary care children's hospital in north India and tested for common respiratory pathogens.

Methods

We randomly enrolled eligible SARI cases aged <5 years from August 2013 to July 2015. SARI cases were defined as either <7-day history of fever with cough or in children aged eight days to three months, a physician diagnosis of acute lower respiratory infection requiring hospitalisation. We also enrolled an age-group matched control without any acute illness in a 2:1 ratio from the outpatient clinic within 24 hours of case enrolment. Nasopharyngeal and/or oropharyngeal swabs were collected and tested using TaqMan Array Cards, a real-time reverse transcription polymerase chain reaction-based multi-pathogen testing platform for selected respiratory viruses among the enrolled cases and controls. We compared the prevalence of each pathogen among cases and controls using the χ2 (χ2) or Fisher exact test (P < 0.05). We used logistic regression to estimate adjusted odds ratios (aORs) which were then used to calculate aetiologic fractions (EFs).

Results

We enrolled 840 cases and 419 outpatient controls. Almost half of the individuals in the whole sample were aged <6 months (n = 521, 41.4%). Females made up 33.7% of cases and 37.2% of controls. Viral detections were more common among cases (69%, 95% confidence interval (CI) = 66, 73) compared to controls (33%; 95% CI = 29, 38) (P < 0.01). RSV (n = 257, 31%; 95% CI = 28, 34%) was the most common virus detected among cases. Influenza A was detected among 24 (3%; 95% CI = 2, 4%), and influenza B among 5 (1%; 95% CI = 0, 1%) cases. The association between the virus and SARI was strongest for RSV (aOR = 23; 95% CI = 12, 47; EF = 96%). Antivirals were administered to 1% of SARI cases while 78% received antibiotics.

Conclusions

Using a multi-pathogen molecular detection method, we detected respiratory viruses among more than two-thirds of children aged <5 years admitted with SARI in the Delhi tertiary care children's hospital. The guidelines for preventing and managing SARI cases among children could be optimised further with the improved availability of antivirals and vaccines.

Incidence of Hospitalization due to Influenza-Associated Severe Acute Respiratory Infection During 2010-2019 in Bangladesh

BACKGROUND

Global influenza-associated acute respiratory infections contribute to 3-5 million severe illnesses requiring hospitalization annually, with 90% of hospitalizations occurring among children < 5 years in developing countries. In Bangladesh, the inadequate availability of nationally representative, robust estimates of influenza-associated hospitalizations limits allocation of resources for prevention and control measures.

METHODS

This study used data from the hospital-based influenza surveillance (HBIS) system in Bangladesh from 2010 to 2019 and healthcare utilization surveys to determine hospital utilization patterns in the catchment area. We estimated annual influenza-associated hospitalization numbers and rates for all age groups in Bangladesh using WHO methods, adjusted for a 6-day-a-week enrollment schedule, selective testing of specimens from children under five, and healthcare-seeking behavior, based on the proportion of symptomatic community participants seeking healthcare within the past week. We then estimated national hospitalization rates by multiplying age-specific hospitalization rates with the corresponding annual national census population.

RESULTS

Annual influenza-associated hospitalization rates per 100,000 population for all ages ranged from 31 (95% CI: 27-36) in 2011 to 139 (95% CI: 130-149) in 2019. Children < 5 years old had the highest rates of influenza-associated hospitalization, ranging from 114 (95% CI: 90-138) in 2011 to 529 (95% CI: 481-578) in 2019, followed by adults aged ≥ 65 years with rates ranging from 46 (95% CI: 34-57) in 2012 to 252 (95% CI: 213-292) in 2019. The national hospitalization estimates for all ages during 2010-2019 ranged from 47,891 to 236,380 per year.

CONCLUSIONS

The impact of influenza-associated hospitalizations in Bangladesh may be considerable, particularly for young children and older adults. Targeted interventions, such as influenza vaccination for these age groups, should be prioritized and evaluated.

P. G, Potdar V, Manna B, Amarchand R, Choudekar A, Gopal G, Sarda K, Lafond KE, Azziz-Baumgartner E, Saha S, Dar L, Krishnan A. Adverse outcomes in patients hospitalized with pneumonia at age 60 or more: A prospective multi-centric hospital-based study in India

BACKGROUND

Limited data exists regarding risk factors for adverse outcomes in older adults hospitalized with Community-Acquired Pneumonia (CAP) in low- and middle-income countries such as India. This multisite study aimed to assess outcomes and associated risk factors among adults aged ≥60 years hospitalized with pneumonia.

METHODS

Between December 2018 and March 2020, we enrolled ≥60-year-old adults admitted within 48 hours for CAP treatment across 16 public and private facilities in four sites. Clinical data and nasal/oropharyngeal specimens were collected by trained nurses and tested for influenza, respiratory syncytial virus (RSV), and other respiratory viruses (ORV) using the qPCR. Participants were evaluated regularly until discharge, as well as on the 7th and 30th days post-discharge. Outcomes included ICU admission and in-hospital or 30-day post-discharge mortality. A hierarchical framework for multivariable logistic regression and Cox proportional hazard models identified risk factors (e.g., demographics, clinical features, etiologic agents) associated with critical care or death.

FINDINGS

Of 1,090 CAP patients, the median age was 69 years; 38.4% were female. Influenza viruses were detected in 12.3%, RSV in 2.2%, and ORV in 6.3% of participants. Critical care was required for 39.4%, with 9.9% in-hospital mortality and 5% 30-day post-discharge mortality. Only 41% of influenza CAP patients received antiviral treatment. Admission factors independently associated with ICU admission included respiratory rate >30/min, blood urea nitrogen>19mg/dl, altered sensorium, anemia, oxygen saturation <90%, prior cardiovascular diseases, chronic respiratory diseases, and private hospital admission. Diabetes, anemia, low oxygen saturation at admission, ICU admission, and mechanical ventilation were associated with 30-day mortality.

CONCLUSION

High ICU admission and 30-day mortality rates were observed among older adults with pneumonia, with a significant proportion linked to influenza and RSV infections. Comprehensive guidelines for CAP prevention and management in older adults are needed, especially with the co-circulation of SARS-CoV-2.

Healthcare-seeking behaviours of patients with acute respiratory infection: a cross-sectional survey in a rural area of southwest China

OBJECTIVES

This study aimed to assess the healthcare-seeking behaviour and related factors of people with acute respiratory symptoms in the rural areas of central and western China to estimate the disease burden of influenza more accurately.

DESIGN

Cross-sectional survey.

SETTINGS

Fifty-two communities/villages in the Wanzhou District, Chongqing, China, a rural area in southwest China, from May 2022 to July 2022.

PARTICIPANTS

The participants were those who had been living in Wanzhou District continuously for more than 6 months and consented to participate.

OUTCOME MEASURES

A semistructured questionnaire was used to determine the healthcare-seeking behaviour of participants, and the dichotomous response of 'yes' or 'no' was used to assess whether participants had acute respiratory symptoms and their healthcare-seeking behaviour.

RESULTS

Only 50.92% (360 of 707) of the patients with acute respiratory infection visited medical and health institutions for treatment, whereas 49.08% (347 of 707) avoided treatment or opted for self-medication. The primary reason for not seeing a doctor was that patients felt their condition was not serious and visiting a medical facility for treatment was unnecessary. Short distance (87.54%) and reasonable charges (49.48%) were ranked as the most important reasons for choosing treatment at primary medical and health facilities (80.27%). The primary reasons for which patients visited secondary and tertiary hospitals (7.78% and 8.61%, respectively) were that doctors in such facilities were better at diagnosis (57.14%) and at treatment (87.10%).

CONCLUSION

The findings provided in this study indicated that regular healthcare-seeking behaviour investigations should be conducted. The disease burden of influenza can be calculated more accurately when healthcare-seeking behaviour investigations are combined with surveillance in the hospitals.

A combination of annual and nonannual forces drive respiratory disease in the tropics

INTRODUCTION

It is well known that influenza and other respiratory viruses are wintertime-seasonal in temperate regions. However, respiratory disease seasonality in the tropics is less well understood. In this study, we aimed to characterise the seasonality of influenza-like illness (ILI) and influenza virus in Ho Chi Minh City, Vietnam.

METHODS

We monitored the daily number of ILI patients in 89 outpatient clinics from January 2010 to December 2019. We collected nasal swabs and tested for influenza from a subset of clinics from May 2012 to December 2019. We used spectral analysis to describe the periodic signals in the system. We evaluated the contribution of these periodic signals to predicting ILI and influenza patterns through lognormal and gamma hurdle models.

RESULTS

During 10 years of community surveillance, 66 799 ILI reports were collected covering 2.9 million patient visits; 2604 nasal swabs were collected, 559 of which were PCR-positive for influenza virus. Both annual and nonannual cycles were detected in the ILI time series, with the annual cycle showing 8.9% lower ILI activity (95% CI 8.8% to 9.0%) from February 24 to May 15. Nonannual cycles had substantial explanatory power for ILI trends (ΔAIC=183) compared with all annual covariates (ΔAIC=263) in lognormal regression. Near-annual signals were observed for PCR-confirmed influenza but were not consistent over time or across influenza (sub)types. The explanatory power of climate factors for ILI and influenza virus trends was weak.

CONCLUSION

Our study reveals a unique pattern of respiratory disease dynamics in a tropical setting influenced by both annual and nonannual drivers, with influenza dynamics showing near-annual periodicities. Timing of vaccination campaigns and hospital capacity planning may require a complex forecasting approach.

Estimation of seasonal influenza disease burden using sentinel site data in Pakistan 2017-2019: A cross-sectional study

Background

The influenza A(H1N1)pdm09 pandemic highlighted the need for reliable disease burden estimation from low- and middle-income countries like Pakistan. We designed retrospective age-stratified estimation of influenza-related severe acute respiratory infections (SARIs) incidence in Islamabad Pakistan 2017-2019.

Materials and Methods

The catchment area was mapped on SARI data from one designated influenza sentinel site and other healthcare facilities in the Islamabad region. The incidence rate was calculated as per 100,000 for each age group with 95% confidence interval.

Results

The catchment population for the sentinel site was 0.7 million against the total denominator of 1.015 million, and incidence rates were adjusted. During January 2017 to December 2019, among 13,905 hospitalizations, 6715 (48%) patients were enrolled; 1208 of these (18%) were positive for influenza. During 2017, influenza A/H3 dominated with 52% detections followed by A(H1N1)pdm09 (35%) and influenza B (13%). Furthermore, elderly 65+ years age group had highest hospitalizations and influenza positive. The incidence rates of all cause respiratory and influenza-related SARI were highest among children >5 years; highest incidence was found in 0 to 11 month/year group with 424/100,000 cases and lowest in 5-15 years 56/100,000. The estimated average annual influenza-associated hospitalization percentage was 29.3% during the study period.

Conclusion

Influenza accounts for a significant proportion of respiratory morbidity and hospitalization. These estimates would enable governments for evidence-based decisions and priority allocation of health resources. It is necessary to test for other respiratory pathogens for more clear disease burden estimation.

Association between climate and infectious diseases among children in Varanasi city, India: A prospective cohort study

The effects of climate on infectious diseases could influence the health impacts, particularly in children in countries with the unfair socioeconomic conditions. In a prospective cohort of 461 children under 16-years-of-age in Varanasi city, India, the association of maximum-temperature (Tmax), relative humidity (RH), absolute humidity (AH), rainfall (RF), wind-speed (WS), and solar radiation (SLR) with prevalent infectious diseases (Diarrhea, Common cold and flu, Pneumonia, Skin-disease and Malaria, and Dengue) was examined using binomial-regression, adjusting for confounders and effect modifiers (socioeconomic-status; SES and child anthropometry), from January 2017 to January 2020. Attributable-fraction (AFx) was calculated due to each climate variable for each infectious disease. The result showed that each unit (1 °C) rise in Tmax was associated with an increase in diarrhea and skin-disease cases by 3.97% (95% CI: 2.92, 5.02) and 3.94% (95% CI: 1.67, 6.22), respectively, whereas, a unit decline in Tmax was associated with an increase in cold and flu cases by 3.87% (95% CI: 2.97, 4.76). Rise in humidity (RH) was associated with increase in cases of cold and flu by 0.73% (95% CI: 0.38, 1.08) and malaria (AH) by 7.19% (95% CI: 1.51, 12.87) while each unit (1 g/m³) decrease in humidity (AH) observed increase in pneumonia cases by 3.02% (95% CI: 0.75, 5.3). WS was positively associated with diarrhea (14.16%; 95% CI: 6.52, 21.80) and negatively with dengue (17.40%; 12.32, 22.48) cases for each unit change (kmph). RF showed marginal association while SLR showed no association at all. The combined AFx due to climatic factors ranged from 9 to 18%. SES and anthropometric parameters modified the climate-morbidity association in children with a high proportion of children found suffering from stunting, wasting, and underweight conditions. Findings from this study draw the attention of government and policymakers to prioritize effective measures for child health as the present association may increase disease burden in the future under climate-change scenarios in already malnourished paediatric population through multiple pathways.

Cohort profile: Indian Network of Population-Based Surveillance Platforms for Influenza and Other Respiratory Viruses among the Elderly (INSPIRE)

PURPOSE

We describe here a multicentric community-dwelling cohort of older adults (>60 years of age) established to estimate incidence, study risk factors, healthcare utilisation and economic burden associated with influenza and respiratory syncytial virus (RSV) in India.

PARTICIPANTS

The four sites of this cohort are in northern (Ballabgarh), southern (Chennai), eastern (Kolkata) and western (Pune) parts of India. We enrolled 5336 participants across 4220 households and began surveillance in July 2018 for viral respiratory infections with additional participants enrolled annually. Trained field workers collected data about individual-level and household-level risk factors at enrolment and quarterly assessed frailty and grip strength. Trained nurses surveilled weekly to identify acute respiratory infections (ARI) and clinically assessed individuals to diagnose acute lower respiratory infection (ALRI) as per protocol. Nasal and oropharyngeal swabs are collected from all ALRI cases and one-fifth of the other ARI cases for laboratory testing. Cost data of the episode are collected using the WHO approach for estimating the economic burden of seasonal influenza. Handheld tablets with Open Data Kit platform were used for data collection.

FINDINGS TO DATE

The attrition of 352 participants due to migration and deaths was offset by enrolling 680 new entrants in the second year. All four sites reported negligible influenza vaccination uptake (0.1%-0.4%), low health insurance coverage (0.4%-22%) and high tobacco use (19%-52%). Ballabgarh had the highest proportion (54.4%) of households in the richest wealth quintile, but reported high solid fuel use (92%). Frailty levels were highest in Kolkata (11.3%) and lowest in Pune (6.8%). The Chennai cohort had highest self-reported morbidity (90.1%).

FUTURE PLANS

The findings of this cohort will be used to inform prioritisation of strategies for influenza and RSV control for older adults in India. We also plan to conduct epidemiological studies of SARS-CoV-2 using this platform.

Efficacy of live attenuated and inactivated influenza vaccines among children in rural India: A 2-year, randomized, triple-blind, placebo-controlled trial

BACKGROUND

Influenza is a cause of febrile acute respiratory infection (FARI) in India; however, few influenza vaccine trials have been conducted in India. We assessed absolute and relative efficacy of live attenuated influenza vaccine (LAIV) and inactivated influenza vaccine (IIV) among children aged 2 to 10 years in rural India through a randomized, triple-blind, placebo-controlled trial conducted over 2 years.

METHODS AND FINDINGS

In June 2015, children were randomly allocated to LAIV, IIV, intranasal placebo, or inactivated polio vaccine (IPV) in a 2:2:1:1 ratio. In June 2016, vaccination was repeated per original allocation. Overall, 3,041 children received LAIV (n = 1,015), IIV (n = 1,010), nasal placebo (n = 507), or IPV (n = 509). Mean age of children was 6.5 years with 20% aged 9 to 10 years. Through weekly home visits, nasal and throat swabs were collected from children with FARI and tested for influenza virus by polymerase chain reaction. The primary outcome was laboratory-confirmed influenza-associated FARI; vaccine efficacy (VE) was calculated using modified intention-to-treat (mITT) analysis by Cox proportional hazards model (PH) for each year. In Year 1, VE was 40.0% (95% confidence interval (CI) 25.2 to 51.9) for LAIV and 59.0% (95% CI 47.8 to 67.9) for IIV compared with controls; relative efficacy of LAIV compared with IIV was -46.2% (95% CI -88.9 to -13.1). In Year 2, VE was 51.9% (95% CI 42.0 to 60.1) for LAIV and 49.9% (95% CI 39.2 to 58.7) for IIV; relative efficacy of LAIV compared with IIV was 4.2% (95% CI -19.9 to 23.5). No serious adverse vaccine-attributable events were reported. Study limitations include differing dosage requirements for children between nasal and injectable vaccines (single dose of LAIV versus 2 doses of IIV) in Year 1 and the fact that immunogenicity studies were not conducted.

CONCLUSIONS

In this study, we found that LAIV and IIV vaccines were safe and moderately efficacious against influenza virus infection among Indian children.

TRIAL REGISTRATION

Clinical Trials Registry of India CTRI/2015/06/005902.

Burden of influenza-associated respiratory and circulatory mortality in India, 2010-2013

Background

Influenza causes substantial morbidity and mortality worldwide, however, reliable burden estimates from developing countries are limited, including India. We aimed to quantify influenza-associated mortality for India utilizing 2010-2013 nationally representative data sources for influenza virus circulation and deaths.

Methods

Virological data were obtained from the influenza surveillance network of 10 laboratories led by National Institute of Virology, Pune covering eight states from 2010-2013. Death data were obtained from the nationally representative Sample Registration System for the same time period. Generalized linear regression with negative binomial distribution was used to model weekly respiratory and circulatory deaths by age group and proportion of specimens positive for influenza by subtype; excess deaths above the seasonal baseline were taken as an estimate of influenza-associated mortality counts and rates. Annual excess death rates and the 2011 India Census data were used to estimate national influenza-associated deaths.

Results

Estimated annual influenza-associated respiratory mortality rates were highest for those ≥65 years (51.1, 95% confidence interval (CI) = 9.2-93.0 deaths/100 000 population) followed by those <5 years (9.8, 95% CI = 0-21.8/100 000). Influenza-associated circulatory death rates were also higher among those ≥65 years (71.8, 95% CI = 7.9-135.8/100 000) as compared to those aged <65 years (1.9, 95% CI = 0-4.6/100 000). Across all age groups, a mean of 127 092 (95% CI = 64 046-190,139) annual influenza-associated respiratory and circulatory deaths may occur in India.

Conclusions

Estimated influenza-associated mortality in India was high among children <5 years and adults ≥65 years. These estimates may inform strategies for influenza prevention and control in India, such as possible vaccine introduction.

Efficacy of inactivated trivalent influenza vaccine in rural India: a 3-year cluster-randomised controlled trial

BACKGROUND

Paediatric vaccination against influenza can result in indirect protection, by reducing transmission to their unvaccinated contacts. We investigated whether influenza vaccination of children would protect them and their household members in a resource-limited setting.

METHODS

We did a cluster-randomised, blinded, controlled study in three villages in India. Clusters were defined as households (ie, dwellings that shared a courtyard), and children aged 6 months to 10 years were eligible for vaccination as and when they became age-eligible throughout the study. Households were randomly assigned (1:1) by a computer-based system to intramuscular trivalent inactivated influenza vaccine (IIV3) or a control of inactivated poliovirus vaccine (IPV) in the beginning of the study; vaccination occurred once a year for 3 years. The primary efficacy outcome was laboratory-confirmed influenza in a vaccinated child with febrile acute respiratory illness, analysed in the modified intention-to-treat population (ie, children who received at least one dose of vaccine, were under surveillance, and had not an influenza infection within 15 days of last vaccine dose). The secondary outcome for indirect effectiveness (surveillance study) was febrile acute respiratory illness in an unvaccinated household member of a vaccine study participant. Data from each year (year 1: November, 2009, to October, 2010; year 2: October, 2010, to October, 2011; and year 3: October, 2011, to May, 2012) were analysed separately. Safety was analysed among all participants who were vaccinated with at least one dose of the vaccine. This trial is registered with ClinicalTrials.gov, number NCT00934245.

FINDINGS

Between Nov 1, 2009, to May 1, 2012, we enrolled 3208 households, of which 1959 had vaccine-eligible children. 1010 households were assigned to IIV3 and 949 households were assigned to IPV. In 3 years, we vaccinated 4345 children (2132 with IIV3 and 2213 with IPV) from 1868 households (968 with IIV3 and 900 with IPV) with 10 813 unvaccinated household contacts. In year 1, influenza virus was detected in 151 (10%) of 1572 IIV3 recipients and 206 (13%) of 1633 of IPV recipients (total IIV3 vaccine efficacy 25·6% [95% CI 6·8-40·6]; p=0·010). In year 2, 105 (6%) of 1705 IIV3 recipients and 182 (10%) of 1814 IPV recipients had influenza (vaccine efficacy 41·0% [24·1-54·1]; p<0·0001). In year 3, 20 (1%) of 1670 IIV3 recipients and 81 (5%) of 1786 IPV recipients had influenza (vaccine efficacy 74·2% [57·8-84·3]; p<0·0001). In year 1, total vaccine efficacy against influenza A(H1N1)pdm09 was 14·5% (-20·4 to 39·3). In year 2, total vaccine efficacy against influenza A(H3N2) was 64·5% (48·5-75·5). Total vaccine efficacy against influenza B was 32·5% (11·3-48·6) in year 1, 4·9% (-38·9 to 34·9) in year 2, and 76·5% (59·4-86·4) in year 3. Indirect vaccine effectiveness was statistically significant only in year 3 (38·1% [7·4-58·6], p=0·0197) when influenza was detected in 39 (1%) of 4323 IIV3-allocated and 60 (1%) of 4121 IPV-allocated household unvaccinated individuals. In the IIV3 group, 225 (12%) of 1632 children in year 1, 375 (22%) of 1718 in year 2, and 209 (12%) of 1673 in year 3 had an adverse reaction (compared with 216 [13%] of 1730, 380 [21%] of 1825, and 235 [13%] of 1796, respectively, in the IPV group). The most common reactions in both groups were fever and tenderness at site. No vaccine-related deaths occurred in either group.

INTERPRETATION

IIV3 provided variable direct and indirect protection against influenza infection. Indirect protection was significant during the year of highest direct protection and should be considered when quantifying the effect of vaccination programmes.

FUNDING

US Centers for Disease Control and Prevention.

Underdetection of laboratory-confirmed influenza-associated hospital admissions among infants: a multicentre, prospective study

BACKGROUND

Since influenza often presents non-specifically in infancy, we aimed to assess the extent to which existing respiratory surveillance platforms might underestimate the frequency of severe influenza disease among infants.

METHODS

The Influenza and Respiratory Syncytial Virus in Infants (IRIS) study was a prospective observational study done at four hospitals in Albania, Jordan, Nicaragua, and the Philippines. We included acutely ill infants aged younger than 1 year admitted to hospital within 10 days or less of illness onset during two influenza seasons (2015-16 and 2016-17) in Albania, Jordan, and Nicaragua, and over a continuous 34 week period (2015-16) in the Philippines. We assessed the frequency of influenza virus infections by real-time RT-PCR (rRT-PCR) and serology. The main study outcome was seroconversion, defined as convalescent antibody titres more than or equal to four-fold higher than acute sera antibody titres, and convalescent antibody titres of 40 or higher. Seroconverison was confirmed by haemagglutination inhibition assay for influenza A viruses, and by hemagglutination inhibition assay and microneutralisation for influenza B viruses.

FINDINGS

Between June 27, 2015, and April 21, 2017, 3634 acutely ill infants were enrolled, of whom 1943 were enrolled during influenza seasons and had complete acute-convalescent pairs and thus were included in the final analytical sample. Of the 1943 infants, 94 (5%) were influenza-positive by both rRT-PCR and serology, 58 (3%) were positive by rRT-PCR-only, and 102 (5%) were positive by serology only. Seroconversion to at least one of the influenza A or B viruses was observed among 196 (77%) of 254 influenza-positive infants. Of the 254 infants with influenza virus, 84 (33%) only had non-respiratory clinical discharge diagnoses (eg, sepsis, febrile seizures, dehydration, or other non-respiratory viral illness). A focus on respiratory diagnoses and rRT-PCR-confirmed influenza underdetects influenza-associated hospital admissions among infants by a factor of 2·6 (95% CI 2·0-3·6). Findings were unchanged when syndromic severe acute respiratory infection criteria were applied instead of clinical diagnosis.

INTERPRETATION

If the true incidence of laboratory-confirmed influenza-associated hospital admissions among infants is at least twice that of previous estimates, this substantially increases the global burden of severe influenza and expands our estimates of the preventive value of maternal and infant influenza vaccination programmes.

FUNDING

US Centers for Disease Control and Prevention.

Progress and Remaining Gaps in Estimating the Global Disease Burden of Influenza

Influenza has long been a global public health priority because of the threat of another global pandemic. Although data are available for the annual burden of seasonal influenza in many developed countries, fewer disease burden data are available for low-income and tropical countries. In recent years, however, the surveillance systems created as part of national pandemic preparedness efforts have produced substantial data on the epidemiology and impact of influenza in countries where data were sparse. These data are leading to greater interest in seasonal influenza, including implementation of vaccination programs. However, a lack of quality data on severe influenza, nonrespiratory outcomes, and high-risk groups, as well as a need for better mathematical models and economic evaluations, are some of the major gaps that remain. These gaps are the focus of multilateral research and surveillance efforts that will strengthen global efforts in influenza control in the future.

The burden of influenza-associated respiratory hospitalizations in Bhutan, 2015-2016

BACKGROUND

Influenza burden estimates help provide evidence to support influenza prevention and control programs. In this study, we estimated influenza-associated respiratory hospitalization rates in Bhutan, a country considering influenza vaccine introduction.

METHODS

Using real-time reverse transcription-polymerase chain reaction laboratory results from severe acute respiratory infection (SARI) surveillance, we estimated the proportion of respiratory hospitalizations attributable to influenza each month among patients aged <5, 5-49, and ≥50 years in six Bhutanese districts for 2015 and 2016. We divided the sum of the monthly influenza-attributed hospitalizations by the total of the six district populations to generate age-specific rates for each year.

RESULTS

In 2015, 10% of SARI patients tested positive for influenza (64/659) and 18% tested positive (129/736) in 2016. The incidence of influenza-associated hospitalizations among all age groups was 50/100 000 persons (95% confidence interval [CI]: 45-55) in 2015 and 118/100 000 persons (95% CI: 110-127) in 2016. The highest rates were among children <5 years: 182/100 000 (95% CI: 153-210) in 2015 and 532/100 000 (95% CI: 473-591) in 2016. The second highest influenza-associated hospitalization rates were among adults ≥50 years: 110/100 000 (95% CI: 91-130) in 2015 and 193/100 000 (95% CI: 165-221) in 2016.

CONCLUSIONS

Influenza viruses were associated with a substantial burden of severe illness requiring hospitalization especially among children and older adults. These findings can be used to understand the potential impact of seasonal influenza vaccination in these age groups.

Influenza-associated paediatric respiratory hospitalizations in China, 1996-2012: a systematic analysis

Background

The World Health Organization recommends that children aged ≥ 6 months be vaccinated against influenza. Influenza vaccination policies depend on the evidence of the burden of influenza, yet few national data on influenza-associated severe outcomes among children exist in China.

Methods

We conducted a systematic review of articles published from 1996 to 2012 on laboratory-confirmed, influenza-associated paediatric respiratory hospitalizations in China. We extracted data and stratified the percentage of samples testing positive for influenza by age group (< 2, < 5 and < 18 years old); case definition; test methods; and geographic location. The pooled percentage of samples testing positive for influenza was estimated with a random effects regression model.

Results

Influenza was associated with 8.8% of respiratory hospitalizations among children aged < 18 years, ranging from 7.0% (95% confidence interval: 4.2–9.8%) in children aged < 2 years to 8.9% (95% confidence interval: 6.8–11%) in children aged < 5 years. The percentage of samples testing positive for influenza was consistently higher among studies with data from children aged < 5 years and < 18 years than those restricted only to children aged < 2 years; the percentages were higher in Northern China than Southern China.

Discussion

Influenza is an important cause of paediatric respiratory hospitalizations in China. Influenza vaccination of school-aged children could prevent substantial influenza-associated illness, including hospitalizations, in China.

Estimation of Burden of Influenza among under-Five Children in India: A Meta-Analysis

BACKGROUND

We estimated the burden of influenza-related acute respiratory tract infection (ARI) among under-fives in India through meta-analysis.

METHODOLOGY

We estimated pooled incidence and proportional positivity of laboratory-diagnosed influenza among under-fives using data from observational studies published from 1 January 1961 to 31 December 2016. Death due to influenza was estimated using a multiplier model.

RESULTS

Influenza-associated ARI incidence was estimated as 132 per 1000 child-years (115-149). The patients positive for influenza among ARI in outpatients and inpatients were estimated to be 11.2% (8.8-13.6) and 7.1% (5.5-8.8), respectively. We estimated total influenza cases during 2016 as 16 009 207 (13 942 916-18 082 769) in India. Influenza accounted for 10 913 476 (9 504 666-12 362 310) outpatient visits and 109 431 (83 882-134 980) hospitalizations. A total of 27 825 (21 382-34 408) influenza-associated under-five deaths were estimated in India in 2016.

CONCLUSION

Influenza imposes a substantial burden among under-fives in India. Public health approach for its prevention and control needs to be explored.

Comparison of incidence and cost of influenza between healthy and high-risk children <60 months old in Thailand, 2011-2015

Introduction

Thailand recommends influenza vaccination for children aged 6 months to <36 months, but investment in vaccine purchase is limited. To inform policy decision with respect to influenza disease burden and associated cost in young children and to support the continued inclusion of children as the recommended group for influenza vaccination, we conducted a prospective cohort study of children in Bangkok hospital to estimate and compare influenza incidence and cost between healthy and high-risk children.

Methods

Caregivers of healthy children and children with medical conditions (‘high-risk’) aged <36 months were called weekly for two years to identify acute respiratory illness (ARI) episodes and collect illness-associated costs. Children with ARI were tested for influenza viruses by polymerase chain reaction. Illnesses were categorized as mild or severe depending on whether children were hospitalized. Population-averaged Poisson models were used to compare influenza incidence by risk group. Quantile regression was used to examine differences in the median illness expenses.

Results

During August 2011-September 2015, 659 healthy and 490 high-risk children were enrolled; median age was 10 months. Incidence of mild influenza-associated ARI was higher among healthy than high-risk children (incidence rate ratio [IRR]: 1.67; 95% confidence interval [CI]: 1.13–2.48). Incidence of severe influenza-associated ARI did not differ (IRR: 0.40; 95% CI: 0.11–1.38). The median cost per mild influenza-associated ARI episode was $22 among healthy and $25 among high-risk children (3–4% of monthly household income; difference in medians: -$1; 95% CI for difference in medians: -$9 to $6). The median cost per severe influenza-associated ARI episode was $232 among healthy and $318 among high-risk children (26–40% and 36–54% of monthly household income, respectively; difference in medians: 110; 95% CI for difference in medians: -$352 to $571).

Conclusions

Compared to high-risk children, healthy children had higher incidence of mild influenza-associated ARI but not severe influenza-associated ARI. Costs of severe influenza-associated ARI were substantial. These findings support the benefit of annual influenza vaccination in reducing the burden of influenza and associated cost in young children.

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

Objective

To estimate rates of community-level influenza-like-illness (ILI) and influenza-associated ILI in rural north India.

Methods

During 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.

Findings

The 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).

Conclusion

We 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.

Report on WHO meeting on immunization in older adults: Geneva, Switzerland, 22-23 March 2017

Many industrialized countries have implemented routine immunization policies for older adults, but similar strategies have not been widely implemented in low- and middle-income countries (LMICs). In March 2017, the World Health Organization (WHO) convened a meeting to identify policies and activities to promote access to vaccination of older adults, specifically in LMICs. Participants included academic and industry researchers, funders, civil society organizations, implementers of global health interventions, and stakeholders from developing countries with adult immunization needs. These experts reviewed vaccine performance in older adults, the anticipated impact of adult vaccination programs, and the challenges and opportunities of building or strengthening an adult and older adult immunization platforms. Key conclusions of the meeting were that there is a need for discussion of new opportunities for vaccination of all adults as well as for vaccination of older adults, as reflected in the recent shift by WHO to a life-course approach to immunization; that immunization in adults should be viewed in the context of a much broader model based on an individual's abilities rather than chronological age; and that immunization beyond infancy is a global priority that can be successfully integrated with other interventions to promote healthy ageing. As WHO is looking ahead to a global Decade of Healthy Ageing starting in 2020, it will seek to define a roadmap for interdisciplinary collaborations to integrate immunization with improving access to preventive and other healthcare interventions for adults worldwide.

Estimated incidence of influenza-associated severe acute respiratory infections in Indonesia, 2013-2016

Background

Indonesia's hospital‐based Severe Acute Respiratory Infection (SARI) surveillance system, Surveilans Infeksi Saluran Pernafasan Akut Berat Indonesia (SIBI), was established in 2013. While respiratory illnesses such as SARI pose a significant problem, there are limited incidence‐based data on influenza disease burden in Indonesia. This study aimed to estimate the incidence of influenza‐associated SARI in Indonesia during 2013‐2016 at three existing SIBI surveillance sites.

Methods

From May 2013 to April 2016, inpatients from sentinel hospitals in three districts of Indonesia (Gunung Kidul, Balikpapan, Deli Serdang) were screened for SARI. Respiratory specimens were collected from eligible inpatients and screened for influenza viruses. Annual incidence rates were calculated using these SIBI‐enrolled influenza‐positive SARI cases as a numerator, with a denominator catchment population defined through hospital admission survey (HAS) to identify respiratory‐coded admissions by age to hospitals in the sentinel site districts.

Results

From May 2013 to April 2016, there were 1527 SARI cases enrolled, of whom 1392 (91%) had specimens tested and 199 (14%) were influenza‐positive. The overall estimated annual incidence of influenza‐associated SARI ranged from 13 to 19 per 100 000 population. Incidence was highest in children aged 0‐4 years (82‐114 per 100 000 population), followed by children 5‐14 years (22‐36 per 100 000 population).

Conclusions

Incidence rates of influenza‐associated SARI in these districts indicate a substantial burden of influenza hospitalizations in young children in Indonesia. Further studies are needed to examine the influenza burden in other potential risk groups such as pregnant women and the elderly.

Cost of Treatment of Febrile Acute Respiratory Infection (FARI) Among Under-Five Children Attending Health Facilities of Ballabgarh, Haryana

OBJECTIVE

To estimate the expenditure incurred towards treatment of an episode of respiratory infection among under-fives in outpatient and inpatient departments of primary and secondary level health facilities.

METHODS

During March 2011 - September 2012, under-five children presenting with febrile acute respiratory infection (FARI) in the outpatient (OPD) and inpatient (IPD) departments of public and private health facilities of Ballabgarh, Haryana were enrolled in the study. Children who were free from co-morbidities and whose contact number or proper address were available, were enrolled and followed up over telephone or by house visits till recovery. Information was collected on expenditure incurred towards treatment of FARI. Work loss of each day was valued as per capita national income per day. Cost of service in public facilities were supplemented by WHO-CHOICE estimates. The cost of respiratory episode in different settings are expressed in median and inter quartile range (IQR).

RESULTS

One hundred fourteen children from OPD and 75 from IPD were enrolled and followed up till recovery. Among eligible children 40% and 20% in OPD and IPD were excluded respectively as they could not provide address or contact number. The median costs of an episode treated in OPD and IPD were INR 447(IQR: INR 294-669) and INR 7506.06 (IQR: INR 3765-10,406) respectively.

CONCLUSIONS

Respiratory infections are responsible for substantial economic burden, especially with huge proportion of out-of-pocket expenditure. Total cost of a respiratory episode that required hospitalization was 1.5 times the per capita monthly income of an Indian.

Influenza Season Hospitalization Trends in Israel: A Multi-Year Comparative Analysis 2005/2006 Through 2012/2013

BACKGROUND

Influenza-related morbidity impacts healthcare systems, including hospitals.

OBJECTIVE

To obtain a quantitative assessment of hospitalization burden in pediatric and internal medicine departments during influenza seasons compared with the summer months in Israel.

METHODS

Data on pediatric and internal medicine hospitalized patients in general hospitals in Israel during the influenza seasons between 2005 and 2013 were analyzed for rate of hospitalizations, rate of hospitalization days, hospital length of stay (LOS), and bed occupancy and compared with the summer months. Data were analyzed for hospitalizations for all diagnoses, diagnoses of respiratory or cardiovascular disease (ICD9 390-519), and influenza or pneumonia (ICD9480-487), with data stratified by age. The 2009-2010 pandemic influenza season was excluded.

RESULTS

Rates of monthly hospitalizations and hospitalization days for all diagnoses were 4.8% and 8% higher, respectively, during influenza seasons as compared with the summers. The mean LOS per hospitalization for all diagnoses demonstrated a small increase during influenza seasons as compared with summer seasons. The excess hospitalizations and hospitalization days were especially noticed for the age groups under 1 year, 1-4 years, and 85 years and older. The differences were severalfold higher for patients with a diagnosis of respiratory or cardiovascular disease and influenza or pneumonia. Bed occupancy was higher during influenza seasons compared with the summer, particularly in pediatric departments.

CONCLUSIONS

Hospital burden in pediatric and internal medicine departments during influenza seasons in Israel was associated with age and diagnosis. These results are important for optimal preparedness for influenza seasons.

Drug resistance in influenza A virus: the epidemiology and management

Influenza A virus (IAV) is the sole cause of the unpredictable influenza pandemics and deadly zoonotic outbreaks and constitutes at least half of the cause of regular annual influenza epidemics in humans. Two classes of anti-IAV drugs, adamantanes and neuraminidase (NA) inhibitors (NAIs) targeting the viral components M2 ion channel and NA, respectively, have been approved to treat IAV infections. However, IAV rapidly acquired resistance against both classes of drugs by mutating these viral components. The adamantane-resistant IAV has established itself in nature, and a majority of the IAV subtypes, especially the most common H1N1 and H3N2, circulating globally are resistant to adamantanes. Consequently, adamantanes have become practically obsolete as anti-IAV drugs. Similarly, up to 100% of the globally circulating IAV H1N1 subtypes were resistant to oseltamivir, the most commonly used NAI, until 2009. However, the 2009 pandemic IAV H1N1 subtype, which was sensitive to NAIs and has now become one of the dominant seasonal influenza virus strains, has replaced the pre-2009 oseltamivir-resistant H1N1 variants. This review traces the epidemiology of both adamantane- and NAI-resistant IAV subtypes since the approval of these drugs and highlights the susceptibility status of currently circulating IAV subtypes to NAIs. Further, it provides an overview of currently and soon to be available control measures to manage current and emerging drug-resistant IAV. Finally, this review outlines the research directions that should be undertaken to manage the circulation of IAV in intermediate hosts and develop effective and alternative anti-IAV therapies.

Influenza and respiratory syncytial virus in infants study (IRIS) of hospitalized and non-ill infants aged <1 year in four countries: study design and methods

Background

This multi-country prospective study of infants aged <1 year aims to assess the frequency of influenza virus and respiratory syncytial virus (RSV) infections associated with hospitalizations, to describe clinical features and antibody response to infection, and to examine predictors of very severe disease requiring intensive care.

Methods/Design

We are enrolling a hospital-based cohort and a sample of non-ill infants in four countries (Albania, Jordan, Nicaragua, and the Philippines) using a common protocol. We are currently starting year 2 of a 2- to 3-year study and will enroll approximately 3,000 infants hospitalized for any acute illness (respiratory or non-respiratory) during periods of local influenza and/or RSV circulation. After informed consent and within 24 h of admission, we collect blood and respiratory specimens and conduct an interview to assess socio-demographic characteristics, medical history, and symptoms of acute illness (onset ≤10 days). Vital signs, interventions, and medications are documented daily through medical record abstraction. A follow-up health assessment and collection of convalescent blood occurs 3-5 weeks after enrollment. Influenza and RSV infection is confirmed by singleplex real time reverse transcriptase polymerase chain reaction (rRT-PCR) assays. Serologic conversion will be assessed comparing acute and convalescent sera using hemagglutination inhibition assay for influenza antibodies and enzyme-linked immunosorbent assay (ELISA) for RSV. Concurrent with hospital-based enrollment, respiratory specimens are also being collected (and tested by rRT-PCR) from approximately 1,400 non-ill infants aged <1 year during routine medical or preventive care.

Discussion

The Influenza and RSV in Infants Study (IRIS) promises to expand our knowledge of the frequency, clinical features, and antibody profiles of serious influenza and RSV disease among infants aged <1 year, quantify the proportion of infections that may be missed by traditional surveillance, and inform decisions about the potential value of existing and new vaccines and other prevention and treatment strategies.

Evaluation of case definitions for estimation of respiratory syncytial virus associated hospitalizations among children in a rural community of northern India

BACKGROUND

The burden estimation studies for respiratory syncytial virus (RSV) have been based on varied case definitions, including case-definitions designed for influenza surveillance systems. We used all medical admissions among children aged 0-59 months to study the effect of case definitions on estimation of RSV-associated hospitalizations rates.

METHODS

The hospital-based daily surveillance enrolled children aged 0-59 months admitted with acute medical conditions from July 2009-December 2012, from a well-defined rural population in Ballabgarh in northern India. All study participants were examined and nasal and throat swabs taken for testing by real-time polymerase chain reaction (RT-PCR) for RSV and influenza virus. Clinical data were used to retrospectively evaluate World Health Organization (WHO) case definitions (2011) commonly used for surveillance of respiratory pathogens, ie, acute respiratory illness (WHO-ARI), severe ARI (SARI) and influenza-like illness (ILI), for determination of RSV-associated hospitalization. RSV-associated hospitalization rates adjusted for admissions at non-study hospitals were calculated.

FINDINGS

Out of 505 children enrolled, 82 (16.2%) tested positive for RSV. Annual incidence rates of RSV-associated hospitalization per 1000 children were highest among infants aged 0-5 months (15.2; 95% confidence interval (CI) 8.3-26.8), followed by ages 6-23 months (5.3, 95% CI 3.2-8.7) and lowest among children 24-59 months (0.5, 95% CI 0.1-1.5). The RSV positive children were more likely to have signs of respiratory distress like wheeze, chest in-drawing, tachypnea, and crepitation compared to RSV-negative based on bivariate comparisons. Other less commonly seen signs of respiratory distress, ie, nasal flaring, grunting, accessory muscle usage were also significantly associated with being RSV positive. Compared to the estimated RSV hospitalization rate based on all medical hospitalizations, the WHO-ARI case definition captured 86% of the total incidence, while case definitions requiring fever like ILI and SARI underestimated the incidence by 50-80%.

CONCLUSIONS

Our study suggests that RSV is a substantial cause of hospitalization among children aged <24months especially those aged <6 months. The WHO-ARI case definition appeared to be the most suitable screening definition for RSV surveillance because of its high sensitivity.

The Global Influenza Hospital Surveillance Network (GIHSN): a new platform to describe the epidemiology of severe influenza

BACKGROUND

Influenza is a global public health problem. However, severe influenza only recently has been addressed in routine surveillance.

OBJECTIVES

The Global Influenza Hospital Surveillance Network (GIHSN) was established to study the epidemiology of severe influenza in consecutive seasons in different countries. Our objective is to describe the GIHSN approach and methods.

METHODS

The GIHSN uses prospective active surveillance to identify consecutive influenza admissions in permanent residents of well-defined geographic areas in sites around the world. A core common protocol is followed. After consent, data are collected on patient characteristics and clinical outcomes, respiratory swabs are obtained, and the presence of influenza virus and subtype or lineage is ascertained by polymerase chain reaction. Data are collated and analyzed at the GIHSN coordination center.

RESULTS

The GIHSN has run its activities for two consecutive influenza seasons, 2012-2013 and 2013-2014, and hospitals in Brazil, China, France, Russian Federation, Turkey, and Spain have been involved in one or both seasons. Consistency on the application of the protocol and heterogeneity for the first season have been addressed in two previous publications. During both seasons, 19 677 eligible admissions were recorded; 11 843 (60%) were included and tested, and 2713 (23%) were positive for influenza: 991 (37%) A(H1N1); 807 (30%) A(H3N2); 583 (21%) B/Yamagata; 56 (2%) B/Victoria and 151 (6%) influenza A; and 125 (5%) influenza B were not characterized.

CONCLUSIONS

The GIHSN is a platform that provides information on severe influenza worldwide, applying a common core protocol and a consistent case definition.

Influenza Burden and Transmission in the Tropics

Each year, influenza causes substantial mortality and morbidity worldwide. It is important to understand influenza in the tropics because of the significant burden in the region and its relevance to global influenza circulation. In this review, influenza burden, transmission dynamics, and their determinants in the tropics are discussed. Environmental, cultural, and social conditions in the tropics are very diverse and often differ from those of temperate regions. Theories that account for and predict influenza dynamics in temperate regions do not fully explain influenza epidemic patterns observed in the tropics. Routine surveillance and household studies have been useful in understanding influenza dynamics in the tropics, but these studies have been limited to only some regions; there is still a lack of information regarding influenza burden and transmission dynamics in many tropical countries. Further studies in the tropics will provide useful insight on many questions that remain.