The national burden of influenza‐like illness and severe respiratory illness overall and associated with nine respiratory viruses in South Africa, 2013–2015

BackgroundEstimates of the disease burden associated with different respiratory viruses are severely limited in low‐ and middle‐income countries, especially in Africa.MethodsWe estimated age‐specific numbers and rates of medically and non‐medically attended influenza‐like illness (ILI) and severe respiratory illness (SRI) that were associated with influenza, respiratory syncytial virus (RSV), rhinovirus, human metapneumovirus, adenovirus, enterovirus and parainfluenza virus types 1–3 after adjusting for the attributable fraction (AF) of virus detection to illness in South Africa during 2013–2015. The base rates were estimated from five surveillance sites and extrapolated nationally.ResultsThe mean annual rates per 100,000 population were 51,383 and 4196 for ILI and SRI, respectively. Of these, 26% (for ILI) and 46% (for SRI) were medically attended. Among outpatients with ILI, rhinovirus had the highest AF‐adjusted rate (7221), followed by influenza (6443) and adenovirus (1364); whereas, among inpatients with SRI, rhinovirus had the highest AF‐adjusted rate (400), followed by RSV (247) and influenza (130). Rhinovirus (9424) and RSV (2026) had the highest AF‐adjusted rates among children aged <5 years with ILI or SRI, respectively, whereas rhinovirus (757) and influenza (306) had the highest AF‐adjusted rates among individuals aged ≥65 years with ILI or SRI, respectively.ConclusionsThere was a substantial burden of ILI and SRI in South Africa during 2013–2015. Rhinovirus and influenza had a prominent disease burden among patients with ILI. RSV and influenza were the most prominent causes of SRI in children and the elderly, respectively.     

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

Background

The 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.

Methods

We 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.

Results

The 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.

Conclusion

The 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.     

Primary care influenza‐like illness surveillance in Ho Chi Minh City,Vietnam 2013‐2015

Background

Year‐round transmission of influenza has been detected in Vietnam through both national surveillance and other epidemiological studies. Understanding the demographic and clinical features of influenza‐like illness (ILI) presenting to primary care in urban Vietnam is vital to understand these transmission dynamics.

Methods

An observational study of patients with ILI in Ho Chi Minh City, Vietnam, was conducted between August 2013 and November 2015 in a mix of public and private primary care settings. Molecular testing for influenza A and influenza B and 12 other respiratory viruses was performed.

Results

A total of 1152 ILI patients were recruited. 322 and 136 subjects tested positive for influenza A and influenza B, respectively. 193 subjects tested positive for another respiratory virus; most commonly rhinovirus and parainfluenza virus 3. Influenza was detected in 81% of the 116 study weeks. Three peaks of influenza activity were detected; an H3N2 peak April‐June 2014, an influenza B peak July‐December 2014, and a mixed H3N2 and H1N1 peak March‐September 2015. Subjects recruited from private clinics were more likely to have higher income and to have reported previous influenza vaccination. Antibiotic use was common (50.3%) despite limited evidence of bacterial infection.

Conclusion

Influenza in southern Vietnam has complex transmission dynamics including periods of intense influenza activity of alternating types and subtypes. Broadening surveillance from hospital to the community in tropical settings is feasible and a valuable for improving our understanding of the global spread and evolution of the virus.     

Cohort profile: A Prospective Household cohort study of Influenza,Respiratory syncytial virus and other respiratory pathogens community burden and Transmission dynamics in South Africa, 2016–2018

PurposeThe PHIRST study (Prospective Household cohort study of Influenza, Respiratory Syncytial virus, and other respiratory pathogens community burden and Transmission dynamics in South Africa) aimed to estimate the community burden of influenza and respiratory syncytial virus (RSV) including the incidence of infection, symptomatic fraction, and to assess household transmission.ParticipantsWe enrolled 1684 individuals in 327 randomly selected households in a rural and an urban site over three consecutive influenza and two RSV seasons. A new cohort of households was enrolled each year. Participants were sampled with nasopharyngeal swabs twice‐weekly during the RSV and influenza seasons of the year of enrolment. Serology samples were collected at enrolment and before and after the influenza season annually.Findings to DateThere were 122 113 potential individual follow‐up visits over the 3 years, and participants were interviewed for 105 783 (87%) of these. Out of 105 683 nasopharyngeal swabs, 1258 (1%) and 1026 (1%) tested positive on polymerase chain reaction (PCR) for influenza viruses and RSV, respectively. Over one third of individuals had PCR‐confirmed influenza each year. Overall, there was influenza transmission to 10% of household contacts of an index case.Future PlansFuture planned analyses include analysis of influenza serology results and RSV burden and transmission. Households enrolled in the PHIRST study during 2016–2018 were eligible for inclusion in a study of SARS‐CoV‐2 transmission initiated in July 2020. This study uses similar testing frequency to assess the community burden of SARS‐CoV‐2 infection and the role of asymptomatic infection in virus transmission.     

Pediatric influenza‐associated myositis – Nebraska, 2001–2007

Objective Influenza‐associated myositis (IAM), characterized by severe lower‐extremity myalgia and reluctance to walk, is a complication of influenza among children. We investigated IAM in Nebraska during six influenza seasons, 2001–2007. Methods During 2006–2007, we requested reports of severe influenza illness among persons aged <18 years and investigated medical records to identify and confirm IAM cases defined as severe myalgia with elevated serum creatinine kinase level in a patient aged <18 years, occurring within 7 days of laboratory confirmed influenza illness onset. Statewide hospital discharge data (HDD) were reviewed to identify retrospectively confirmed IAM cases during 2006–2007 and five previous seasons, by using surveillance data to define periods of influenza activity. Statewide IAM incidence was estimated for 2001–2002 through 2006–2007. Results During 2006–2007, a total of 13 IAM cases were confirmed by enhanced surveillance. Median age was 6 years (range, 4–11 years). Influenza diagnosis was established by viral isolation from six patients (one influenza A and five influenza B) and rapid diagnostic tests for seven. Twelve (92%) patients, including one who died, were hospitalized for a median of 3 days (range, 1–4 days). Review of HDD identified 12 retrospectively confirmed IAM cases during 2006–2007, including four not reported through enhanced surveillance, and only one during five previous seasons (2003–2004). The HDD‐derived, retrospectively confirmed statewide IAM incidence estimates/1 00 000 population aged <18 years were 2·693 and 0·225 during 2006–2007 and 2003–2004, respectively. Conclusion An IAM epidemic occurred in Nebraska during the 2006–2007 influenza season.     

Human respiratory syncytial virus diversity and epidemiology among patients hospitalized with severe respiratory illness in South Africa, 2012–2015

BackgroundWe aimed to describe the prevalence of human respiratory syncytial virus (HRSV) and evaluate associations between HRSV subgroups and/or genotypes and epidemiologic characteristics and clinical outcomes in patients hospitalized with severe respiratory illness (SRI).MethodsBetween January 2012 and December 2015, we enrolled patients of all ages admitted to two South African hospitals with SRI in prospective hospital‐based syndromic surveillance. We collected respiratory specimens and clinical and epidemiological data. Unconditional random effect multivariable logistic regression was used to assess factors associated with HRSV infection.ResultsHRSV was detected in 11.2% (772/6908) of enrolled patients of which 47.0% (363/772) were under the age of 6 months. There were no differences in clinical outcomes of HRSV subgroup A‐infected patients compared with HRSV subgroup B‐infected patients but among patients aged <5 years, children with HRSV subgroup A were more likely be coinfected with Streptococcus pneumoniae (23/208, 11.0% vs. 2/90, 2.0%; adjusted odds ratio 5.7). No significant associations of HRSV A genotypes NA1 and ON1 with specific clinical outcomes were observed.ConclusionsWhile HRSV subgroup and genotype dominance shifted between seasons, we showed similar genotype diversity as noted worldwide. We found no association between clinical outcomes and HRSV subgroups or genotypes.     

Economic burden of influenza‐associated hospitalizations and outpatient visits in Bangladesh during 2010

Objective

Understanding the costs of influenza-associated illness in Bangladesh may help health authorities assess the cost-effectiveness of influenza prevention programs. We estimated the annual economic burden of influenza-associated hospitalizations and outpatient visits in Bangladesh.

Design

From May through October 2010, investigators identified both outpatients and inpatients at four tertiary hospitals with laboratory-confirmed influenza infection through rRT-PCR. Research assistants visited case-patients'' homes within 30 days of hospital visit/discharge and administered a structured questionnaire to capture direct medical costs (physician consultation, hospital bed, medicines and diagnostic tests), direct non-medical costs (food, lodging and travel) and indirect costs (case-patients'' and caregivers'' lost income). We used WHO-Choice estimates for routine healthcare service costs. We added direct, indirect and healthcare service costs to calculate cost-per-episode. We used median cost-per-episode, published influenza-associated outpatient and hospitalization rates and Bangladesh census data to estimate the annual economic burden of influenza-associated illnesses in 2010.

Results

We interviewed 132 outpatients and 41 hospitalized patients. The median cost of an influenza-associated outpatient visit was US$4.80 (IQR = 2.93–8.11) and an influenza-associated hospitalization was US$82.20 (IQR = 59.96–121.56). We estimated that influenza-associated outpatient visits resulted in US$108 million (95% CI: 76–147) in direct costs and US$59 million (95% CI: 37–91) in indirect costs; influenza-associated hospitalizations resulted in US$1.4 million (95% CI: 0.4–2.6) in direct costs and US$0.4 million (95% CI: 0.1–0.8) in indirect costs in 2010.

Conclusions

In Bangladesh, influenza-associated illnesses caused an estimated US$169 million in economic loss in 2010, largely driven by frequent but low-cost outpatient visits.     

Effectiveness of seasonal influenza vaccinations against laboratory‐confirmed influenza‐associated infections among Singapore military personnel in 2010–2013

Background

Limited information is available about seasonal influenza vaccine effectiveness (VE) in tropical communities.

Objectives

Virus subtype-specific VE was determined for all military service personnel in the recruit camp and three other non-recruit camp in Singapore''s Armed Forces from 1 June 2009 to 30 June 2012.

Methods

Consenting servicemen underwent nasal washes, which were tested with RT-PCR and subtyped. The test positive case and test negative control design was used to estimate the VE. To estimate the overall effect of the programme on new recruits, we used an ecological time series approach.

Results

A total of 7016 consultations were collected. The crude estimates for the VE of the triavalent vaccine against both influenza A(H1N1)pdm09 and influenza B were 84% (95% CI 78–88%, 79–86%, respectively). Vaccine efficacy against influenza A(H3N2) was markedly lower (VE 33%, 95% CI −4% to 57%). An estimated 70% (RR = 0·30; 95% CI 0·11–0·84), 39% (RR = 0·61;0·25–1·43) and 75% (RR = 0·25; 95% CI 0·11–0·50) reduction in the risk of influenza A(H1N1)pdm09, influenza A(H3N2) and influenza B infections, respectively, in the recruit camp during the post-vaccination period compared with during the pre-vaccination period was observed.

Conclusions

Overall, the blanket influenza vaccine programme in Singapore''s Armed Forces has had a moderate to high degree of protection against influenza A(H1N1)pdm09 and influenza B, but not against influenza A(H3N2). Blanket influenza vaccination is recommended for all military personnel.     

Interim estimates of the effectiveness of influenza vaccination against influenza‐associated hospitalization in children in Hong Kong, 2015–16

From 1 September 2015 through 31 January 2016, we enrolled 2068 children 6 months to 17 years of age admitted to hospital with a febrile acute respiratory infection in our test‐negative study. Information on receipt of 2015–16 northern hemisphere inactivated influenza vaccination was elicited from parents or legal guardians. Using conditional logistic regression adjusting for age and matching on calendar time, we estimated influenza vaccine effectiveness against hospitalization with influenza A or B to be 79.2% (95% confidence interval: 42.0%–92.4%). Annual influenza vaccination should be more widely used in children in Hong Kong.     

The burden of influenza among Kenyan pregnant and postpartum women and their infants, 2015–2020

BackgroundIn tropical Africa, data about influenza‐associated illness burden are needed to assess potential benefits of influenza vaccination among pregnant women. We estimated the incidence of influenza among pregnant women and their infants in Siaya County, Kenya.MethodsWe enrolled women at <31 weeks of gestation and conducted weekly follow‐up until 6‐month postpartum to identify acute respiratory illnesses (ARIs). We defined ARI among mothers as reported cough, rhinorrhoea or sore throat and among infants as maternal‐reported cough, difficulty breathing, rhinorrhoea or clinician diagnosis of respiratory illness. We collected nasal/nasopharyngeal and oropharyngeal swabs from mothers/infants with ARI and tested for influenza A and B using molecular assays. We calculated antenatal incidence of laboratory‐confirmed influenza among mothers and postnatal incidence among mothers and infants.ResultsDuring June 2015 to May 2020, we analysed data from 3,026 pregnant women at a median gestational age of 16 weeks (interquartile range [IQR], 13, 18) and followed 2,550 infants. Incidence of laboratory‐confirmed influenza during pregnancy (10.3 episodes per 1,000 person‐months [95% confidence interval {CI} 8.6–11.8]) was twofold higher than in the postpartum period (4.0 [95% CI 2.6–5.5]; p < 0.01). Incidence was significantly higher among human immunodeficiency virus (HIV)‐infected pregnant women (15.6 [95% CI 11.0–20.6] vs. 9.1 [95% CI 7.5–10.8]; p < 0.01). Incidence among young infants was 4.4 (95% CI 3.0–5.9) and similar among HIV‐exposed and HIV‐unexposed infants.ConclusionOur findings suggest a substantial burden of influenza illnesses during pregnancy, with a higher burden among HIV‐infected mothers. Kenyan authorities should consider the value of vaccinating pregnant women, especially if HIV infected.