Relationship between the population incidence of febrile convulsions in young children in Sydney, Australia and seasonal epidemics of influenza and respiratory syncytial virus, 2003-2010: a time series analysis

Snotwatch: an ecological analysis of the relationship between febrile seizures and respiratory virus activity

Background

Febrile seizures are the commonest type of seizure in occurring in the first few years of life, mostly affecting children aged six months to five years old. While largely benign, the incidence of each febrile seizure increases the risk of recurrence, afebrile seizures and epilepsy. Viruses are the most frequent cause of febrile illnesses in which a febrile seizure occurs. Febrile seizure presentation patterns appear to follow a seasonal trend.

Aims

To identify patterns of febrile seizure incidence across different seasons with specific viral activity, and to establish a framework for analysing virus circulation data with common illnesses within a shared region and population.

Setting

Our study was a study of febrile seizure presentations in Victoria, Australia and respiratory virus detection.

Participants

We obtained independent datasets of emergency department febrile seizure presentations at Monash Health and all respiratory multiplex PCR tests performed at Monash Health from January 2010–December 2019 to observe common trends in virus circulation and febrile seizure incidence.

Study design

Trends were studied temporally through mixed effects Poisson regression analysis of the monthly incidence of febrile seizures and the rate of positive PCR tests. Peak viral seasons (95th centile incidence) were compared to median viral circulation (50th centile incidence) to calculate peak season risk ratios.

Results

We found a 1.75–2.06 annual risk ratio of febrile seizure incidence in June–September. Temporal analysis of our data showed this peak in febrile seizures was attributable to circulating viruses in this season, and virus modelling showed correlation with increased rates of positive Influenza A (1.48 peak season risk ratio), Influenza B (1.31 peak season risk ratio), Human metapneumovirus (1.19 peak season risk ratio) and Respiratory Syncytial Virus (1.53 peak season risk ratio) on PCR testing.

Conclusion

Our ecological study statistically demonstrates the recognised winter peak in febrile seizure incidence and ascribes the seasonal relationship to several viral infections which affect the community, including a novel association with Human metapneumovirus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03222-4.

Seasonal distribution of febrile seizure and the relationship with respiratory and enteric viruses in Korean children based on nationwide registry data

PURPOSE

The seasonal distribution patterns of febrile seizures and of respiratory and enteric viral pathogens are similar. In this study, we analyzed trends in febrile seizures and viral infection in Korean children, using big data from the Korean Health Insurance Review and Assessment Service (HIRA).

METHODS

We analyzed children younger than 6 years who visited the hospital and were diagnosed with febrile seizures from 2009 to 2016, using medical records in the HIRA database. A total of 666,136 medical records of children with a main or subdiagnosis of febrile seizure from 2008 to 2016 were included. Of these records, patients younger than 1 month and records before 2009 were excluded. Finally, 558,130 records were extracted.

RESULTS

The medical records included 315,774 male children and 242,356 (43.4%) female children, with a mean age of 2.31 ± 1.31 years. The annual incidence of febrile seizure was 25.4 per 1000 person-years (27.9 for boys and 22.7 for girls). The ratio of male to female children was 1.30: 1, and records of 1-year-old children comprised the highest proportion (n = 210,400, 33.70%). The total monthly number of patients was highest in May (n = 64,969, 11.6%), and peaks were formed from April to July. The fewest patients were seen in October (n = 34,424, 6.17%). The most common viral pathogens were influenza in April and enterovirus during May-July.

CONCLUSION

The seasonal distribution of febrile seizures was high from late spring to summer, and influenza virus and enterovirus were most frequently associated.

Influenza virus seroincidence in a cohort of healthy and high-risk children enrolled in infancy, Bangkok, Thailand

BACKGROUND

We measured seroconversion to influenza viruses and incidence of symptomatic influenza virus infection in a cohort of children in Bangkok, Thailand.

METHODS

Children aged ≤6 months were followed for two years for acute respiratory illness (ARI) and had serum specimens taken at 6-month intervals and tested by hemagglutination inhibition (HI) assay. Seroconversion was defined as a >4-fold rise in the HI titers between time points with a titer of >40 in the second specimen. Respiratory swabs were tested by rRT-PCR for influenza. Data were analyzed using generalized linear models.

RESULTS

Of 350 children, 266 (76%, 147 were healthy and 119 were high-risk) had ≥2 serum specimens collected before influenza vaccination. During the 2-year follow-up, 266 children contributed 370 person-years of observation, excluding post-vaccination periods. We identified 32 ARI cases with rRT-PCR-confirmed influenza virus infection (7 infections/100 person-years, 95% confidence interval [CI], 4-11). There were 126 episodes of influenza virus infection, resulting in a seroconversion rate of 35 infections/100 person-years (95% CI, 30-42). Rates in healthy and high-risk children did not differ.

CONCLUSIONS

Influenza virus infection is common during the first two years of life among Thai children. A large proportion of infections may not be detected using the ARI case definition.

Temporal relationship between occurrences of hand, foot and mouth disease, respiratory virus detection and febrile seizures in children in tropical Singapore: a time-series analysis

Febrile seizure (FS) in children is a common complication of infections with respiratory viruses and hand, foot and mouth disease (HFMD). We conducted a retrospective ecological time-series analysis to determine the temporal relationship between hospital attendances for FS and HFMD or respiratory virus infections. Epilepsy attendance was used as a control. Data from 2004 to 2012 FS and epilepsy hospital attendance, HFMD notifications to the Ministry of Health and from laboratory-confirmed viral respiratory infections among KK Women's and Children's Hospital inpatients were used. A multivariate linear regression analysis was conducted to evaluate the relationship between FS and the virus time series. Relative risks of FS by age were calculated using Bayesian statistical methods. Paediatric accident and emergency (A&E) attendances for FS were found to be associated with influenza A (extra 0.47 FS per influenza A case), B (extra 0.32 per influenza B case) and parainfluenza 3 (extra 0.35 per parainfluenza type 3 case). However, other viruses were not significantly associated with FS. None of the viruses were associated with epileptic seizure attendance. Influenza A, B and parainfluenza 3 viruses contributed to the burden of FS resulting in A&E attendance. Children at risk of FS should be advised to receive seasonal influenza vaccination.

Atherosclerosis, Periodontal Disease, and Treatment with Resolvins

PURPOSE OF REVIEW

This review aims to discuss the existing evidence on the link between atherosclerosis and periodontitis by particularly presenting new findings that link the pathology and therapy of these diseases. Acute vascular ischemic events that can lead to stroke or myocardial infarction are initiated by inflammatory processes leading to rupture or erosion of plaques susceptible to thrombosis ("high risk" or "vulnerable"). These are highly inflamed plaques residing in the media and adventitia that may not be detected by angiography measurments of luminal narrowing. Statistically significant excess risk for atherosclerotic cardiovascular disease has been reported in persons with periodontitis independent of established risk factors. We hypothesized that the systemic pathologic links also represent potential therapeutic links.

RECENT FINDINGS

We recently demonstrated that periodontal inflammation promotes atherosclerotic plaque inflammation and destabilization. As discrete pathological regions, these plaques with a high susceptibility to rupture can be imaged and differentiated from lower risk plaques. In cholesterol-fed rabbits with periodontal disease, circulating inflammatory mediators were also significantly elevated thereby contributing to "vulnerable blood," a systemic characteristic of high risk for cardiovascular events. New studies show that certain lipid mediators, including lipoxins and resolvins, are potent in preventing and possibly treating a number of inflammation-associated diseases, including periodontitis and vascular inflammation. The concept of the vulnerable patient and the pro-resolving approach open new terrain for discovery of paradigm-changing therapies for the prevention and treatment of two of the most common diseases of man. Importantly, lipoxins and resolvins are natural receptor agonists that do not exhibit the same pro-atherogenic side effects attributed to anti-inflammatory medications (e.g., NSAIDs) but rather coordinate resolution of inflammation and a return to homeostasis.

Emergency Department demand associated with seasonal influenza, 2010 through 2014, New South Wales, Australia

Introduction

Influenza’s impact on health and health care is underestimated by influenza diagnoses recorded in health-care databases. We aimed to estimate total and non-admitted influenza-attributable hospital Emergency Department (ED) demand in New South Wales (NSW), Australia.

Methods

We used generalized additive time series models to estimate the association between weekly counts of laboratory-confirmed influenza infections and weekly rates of total and non-admitted respiratory, infection, cardiovascular and all-cause ED visits in NSW, Australia for the period 2010 through 2014. Visit categories were based on the coded ED diagnosis or the free-text presenting problem if no diagnosis was recorded.

Results

The estimated all-age, annual influenza-attributable respiratory, infection, cardiovascular and all-cause visit rates/100 000 population/year were, respectively, 120.6 (99.9% confidence interval [CI] 102.3 to 138.8), 79.7 (99.9% CI: 70.6 to 88.9), 14.0 (99.9% CI: 6.8 to 21.3) and 309.0 (99.9% CI: 208.0 to 410.1). Among respiratory visits, influenza-attributable rates were highest among < 5-year-olds and ≥ 85-year-olds. For infection and all-cause visits, rates were highest among children; cardiovascular rates did not vary significantly by age. Annual rates varied substantially by year and age group, and statistically significant associations were absent in several years or age groups. Of the respiratory visits, 73.4% did not require admission. The non-admitted proportion was higher for the other clinical categories. Around 1 in 100 total visits and more than 1 in 10 respiratory or infection visits were associated with influenza.

Discussion

Influenza is associated with a substantial and annually varying burden of hospital-attended illness in NSW.

Respiratory and Enteric Virus Detection in Children

The majority of children with febrile seizures have viral infections and viruses were detected in 22% to 63% of children in published studies. Using molecular methods, viruses were also detected in asymptomatic persons. A prospective study was conducted to detect respiratory and enteric viruses in 192 children with febrile seizures and compare the detection rates to those found in 156 healthy age-matched controls. A respiratory or enteric virus was detected in 72.9% of children with febrile seizures and in 51.4% of healthy controls. The viruses most strongly associated with febrile seizures were influenza, respiratory syncytial virus, parainfluenza, human coronavirus, and rotavirus. Compared to healthy controls, the age-adjusted odds ratios for nasopharynx virus positivity in febrile seizure patients were 79.4, 2.8, 7.2, and 4.9 for influenza virus, parainfluenza virus, respiratory syncytial virus, and human coronavirus, respectively, and 22.0 for rotavirus in stool. The detected virus did not influence clinical features of febrile seizure.

Time series analysis of RSV and bronchiolitis seasonality in temperate and tropical Western Australia

Respiratory syncytial virus (RSV) causes respiratory illness in young children and is most commonly associated with bronchiolitis. RSV typically occurs as annual or biennial winter epidemics in temperate regions, with less pronounced seasonality in the tropics. We sought to characterise and compare the seasonality of RSV and bronchiolitis in temperate and tropical Western Australia. We examined over 13 years of RSV laboratory identifications and bronchiolitis hospitalisations in children, using an extensive linked dataset from Western Australia. We applied mathematical time series analyses to identify the dominant seasonal cycle, and changes in epidemic size and timing over this period. Both the RSV and bronchiolitis data showed clear winter epidemic peaks in July or August in the southern Western Australia regions, but less identifiable seasonality in the northern regions. Use of complex demodulation proved very effective at comparing disease epidemics. The timing of RSV and bronchiolitis epidemics coincided well, but the size of the epidemics differed, with more consistent peak sizes for bronchiolitis than for RSV. Our results show that bronchiolitis hospitalisations are a reasonable proxy for the timing of RSV detections, but may not fully capture the magnitude of RSV epidemics.

The burden of seasonal and pandemic influenza in infants and children

The burden of influenza is unevenly distributed, with more severe outcomes in children aged <5 years than older children and adults. In spite of this, immunisation policies for young children are far from universal. This article provides an overview of the published evidence on the burden of influenza in children worldwide, with a particular interest in the impact of pandemic influenza in 2009-2010 (caused by the H1N1pdm09 virus). In an average season, up to 9.8 % of 0- to 14-year olds present with influenza, but incidence rates can be markedly higher in younger children. Children aged <5 years have greater rates of hospitalisation and complications than their older counterparts, particularly if the children have co-existing illnesses; historically, this age group have had higher mortality rates from the disease than other children, although during the 2009-2010 pandemic the median age of those who died of influenza was higher than in previous seasons. Admissions to hospital and emergency departments appear to have been more frequent in children with H1N1pdm09 infections than during previous seasonal epidemics, with pneumonia continuing to be a common complication in this setting. Outcomes in children hospitalised with severe disease also seem to have been worse for those infected with H1N1pdm09 viruses compared with seasonal viruses. Studies in children confirm that vaccination reduces the incidence of seasonal influenza and the associated burden, underlining the importance of targeting this group in national immunisation policies.

CONCLUSIONS

Children aged <5 years are especially vulnerable to influenza, particularly that caused by seasonal viruses, and vaccination in this group can be an effective strategy for reducing disease burden.

The risk of fever following one dose of trivalent inactivated influenza vaccine in children aged ≥6 months to <36 months: a comparison of published and unpublished studies

There are limited summary data published on the risk of fever and febrile seizures in children following influenza vaccination. We performed a review of the risk of fever and febrile seizures following receipt of trivalent inactivated influenza vaccine (TIV) in children aged ≥6 months to <36 months, searching PubMED and Google Scholar for English language articles from 2000 onwards, and initiated or ongoing unpublished studies since September 2007 using Clinicaltrials.gov. Exclusions included other vaccine co-administration, missing ages or participant numbers, or unmeasured fever. We reviewed articles and collated results using a standard data extraction template. We identified a total of 909 published papers and unpublished trials from a search conducted on 23 January 2013, 669 from Google Scholar, 114 from PubMed and 126 from the Clinicaltrials.gov online database. After excluding 890 published papers or unpublished trials, 5 published papers and 14 unpublished trials were included in this review. Extracted data on number of events, children at risk and time of follow-up were converted to the risk of fever, which was averaged per week of follow-up (referred to as 'averaged weekly risk'). Following one dose of TIV, the median averaged weekly risk of any fever (≥37.5°C) was 26.0% (range 10.3-70.0%) in unpublished trials compared to 8.2% (range 5.3-28.3%) in published papers (p=0.04). The median averaged weekly risk of severe fever (≥39.0°C) was 3.2% (range 0-10.0%) and 2.0% (range 0.6-17.0%), respectively (p=0.91). Variation in the reporting of fever by participant age groups, time since vaccination and the definition or measurement of fever resulted in a wide range of risk estimates. Reporting of febrile reactions should be standardised to allow comparison between manufacturers and influenza seasons.

Syndromic surveillance for influenza in the emergency department-A systematic review

The science of surveillance is rapidly evolving due to changes in public health information and preparedness as national security issues, new information technologies and health reform. As the Emergency Department has become a much more utilized venue for acute care, it has also become a more attractive data source for disease surveillance. In recent years, influenza surveillance from the Emergency Department has increased in scope and breadth and has resulted in innovative and increasingly accepted methods of surveillance for influenza and influenza-like-illness (ILI). We undertook a systematic review of published Emergency Department-based influenza and ILI syndromic surveillance systems. A PubMed search using the keywords "syndromic", "surveillance", "influenza" and "emergency" was performed. Manuscripts were included in the analysis if they described (1) data from an Emergency Department (2) surveillance of influenza or ILI and (3) syndromic or clinical data. Meeting abstracts were excluded. The references of included manuscripts were examined for additional studies. A total of 38 manuscripts met the inclusion criteria, describing 24 discrete syndromic surveillance systems. Emergency Department-based influenza syndromic surveillance has been described worldwide. A wide variety of clinical data was used for surveillance, including chief complaint/presentation, preliminary or discharge diagnosis, free text analysis of the entire medical record, Google flu trends, calls to teletriage and help lines, ambulance dispatch calls, case reports of H1N1 in the media, markers of ED crowding, admission and Left Without Being Seen rates. Syndromes used to capture influenza rates were nearly always related to ILI (i.e. fever +/- a respiratory or constitutional complaint), however, other syndromes used for surveillance included fever alone, "respiratory complaint" and seizure. Two very large surveillance networks, the North American DiSTRIBuTE network and the European Triple S system have collected large-scale Emergency Department-based influenza and ILI syndromic surveillance data. Syndromic surveillance for influenza and ILI from the Emergency Department is becoming more prevalent as a measure of yearly influenza outbreaks.

Risk of presentation to hospital with epileptic seizures after vaccination with monovalent AS03 adjuvanted pandemic A/H1N1 2009 influenza vaccine (Pandemrix): self controlled case series study

OBJECTIVE

To assess the risk of epileptic seizures in people with and without epilepsy after vaccination with a monovalent AS03 adjuvanted pandemic A/H1N1 influenza vaccine (Pandemrix; Glaxo SmithKline, Sweden).

DESIGN

Register based self controlled case series.

SETTING

Three Swedish counties (source population 750,000).

PARTICIPANTS

373,398 people (age 0-106, median 41.2) who were vaccinated. Vaccinated people with epileptic seizures, diagnosed as inpatients or outpatients, at any time from 90 days before until 90 days after any dose of vaccine.

MAIN OUTCOME MEASURES

Endpoints were admission to hospital or outpatient hospital care with epileptic seizures as the main diagnosis. The effect estimate of relative incidence was calculated as the incidence of epileptic seizures in period after exposure relative to the incidence of epileptic seizures in two control periods, one before and one after vaccination.

RESULTS

859 people experienced epileptic seizures during the study period. There was no increased risk of seizures in people with previously diagnosed epilepsy (relative incidence 1.01, 95% confidence interval 0.74 to 1.39) and a non-significant decrease in risk for people without epilepsy (0.67, 0.27 to 1.65) during the day 1-7 risk period (where day 1 is the day of vaccination). In a second risk period (day 8-30), there was a non-significant increased risk of seizures in people without epilepsy (1.11, 0.73 to 1.70) but no increase in risk for those with epilepsy (1.00, 0.83 to 1.21).

CONCLUSIONS

This study found no evidence of an increase in risk of presentation to hospital with epileptic seizures after vaccination with a monovalent AS03 adjuvanted pandemic H1N1 influenza vaccine.

Signal identification and evaluation for risk of febrile seizures in children following trivalent inactivated influenza vaccine in the Vaccine Safety Datalink Project, 2010-2011

In fall 2010 in the southern hemisphere, an increased risk of febrile seizures was noted in young children in Australia in the 24 h after receipt of trivalent inactivated influenza vaccine (TIV) manufactured by CSL Biotherapies. Although the CSL TIV vaccine was not recommended for use in young children in the US, during the 2010-2011 influenza season near real-time surveillance was conducted for febrile seizures in the 0-1 days following first dose TIV in a cohort of 206,174 vaccinated children ages 6 through 59 months in the Vaccine Safety Datalink Project. On a weekly basis, surveillance was conducted with the primary approach of a self-controlled risk interval design and the secondary approach of a current vs. historical vaccinee design. Sequential statistical methods were employed to account for repeated analyses of accumulating data. Signals for seizures based on computerized data were identified in mid November 2010 using a current vs. historical design and in late December 2010 using a self-controlled risk interval design. Further signal evaluation was conducted with chart-confirmed febrile seizure cases using only data from the primary approach (i.e. self-controlled risk interval design). The magnitude of the incidence rate ratio and risk difference comparing risk of seizures in the 0-1 days vs. 14-20 days following TIV differed by receipt of concomitant 13-valent pneumococcal conjugate vaccine (PCV13). Among children 6-59 months of age, the incidence rate ratio (IRR) for TIV adjusted for concomitant PCV13 was 2.4 (95% CI 1.2, 4.7) while the IRR for PCV13 adjusted for concomitant TIV was 2.5 (95% CI 1.3, 4.7). The IRR for concomitant TIV and PCV13 was 5.9 (95% CI 3.1, 11.3). Risk difference estimates varied by age due to the varying baseline risk for seizures in young children, with the highest estimates occurring at 16 months (12.5 per 100,000 doses for TIV without concomitant PCV13, 13.7 per 100,000 doses for PCV13 without concomitant TIV, and 44.9 per 100,000 doses for concomitant TIV and PCV13) and the lowest estimates occurring at 59 months (1.1 per 100,000 doses for TIV without concomitant PCV13, 1.2 per 100,000 doses for PCV13 without concomitant TIV, and 4.0 per 100,000 doses for concomitant TIV and PCV13). Incidence rate ratio and risk difference estimates were lower for children receiving TIV without concomitant PCV13 or PCV13 without concomitant TIV. Because of the importance of preventing influenza and pneumococcal infections and associated complications, our findings should be placed in a benefit-risk framework to ensure that population health benefits are maximized.