Estimating seasonal variation in Australian pertussis notifications from 1991 to 2016: evidence of spring to summer peaks

Pertussis seasonal variation in Northern Vietnam: the evidence from a tertiary hospital

BACKGROUND

Pertussis is a highly contagious and dangerous respiratory disease that threatens children's health in many countries, including Vietnam, despite vaccine coverage. From 2015 to 2018, Vietnam experienced an increasing number of pertussis patients. Therefore, this study aimed to investigate the trend and examine the seasonal variations of pertussis in North Vietnam.

METHODS

Data were collected from medical records of all under-5-year-old inpatients admitted to the National Children's Hospital in Hanoi, Vietnam (VNCH) 2015-2018. A descriptive analysis was performed to describe the distribution of incident cases by year and season. Linear multivariable regression was conducted to investigate the association between the incidence of cases and seasonality adjusted by age and vaccination status.

RESULTS

We identified 1063 laboratory-confirmed patients during 2015-2018, including 247 (23.2%) severe patients. The number of pertussis patients admitted to VNCH per 1000 hospitalizations was 3.2 in 2015, compared to 1.9, 3.1, and 2.1 in 2016, 2017, and 2018, respectively. Outbreaks occurred biennially; however, there was no significant difference in the number of severe patients over this period. Most cases occurred in the hot season (509 patients, or nearly half of the study population). With the adjustment of the vaccination rate and average age, the risk of pertussis-associated hospitalization in the mild season and the hot season was 21% (95% CI [0.12; 0.3]) and 15% (95% CI [0.05; 0.25]) higher than that in the warm season, respectively. The rate of hospitalizations was high in the mild season (28.9%) and the warm season (30.8%), nearly twice as much as that in the hot season; nevertheless, the death rate was only striking high in the mild season, about 5-6 times as much as those in the other seasons.

CONCLUSION

The pertussis incidence in Northern Vietnam varied between seasons, peaking in the hot season (April-July). However, severe patients and deaths increased in the mild season (December-March). Interventions, for example, communication activities on pertussis and vaccination, are of immense importance in lowering the prevalence of pertussis. In addition, early diagnoses and early warnings performed by health professionals should be encouraged.

Population-Based Study of Pertussis Incidence and Risk Factors among Persons >50 Years of Age, Australia

Despite vaccination programs, pertussis has been poorly controlled, especially among older adults in Australia. This longitudinal, retrospective, observational study aimed to estimate the incidence and risk factors of pertussis among persons ≥50 years of age in Australia in the primary care setting, including those with underlying chronic obstructive pulmonary disease (COPD) or asthma. We used the IQVIA general practitioner electronic medical record database to identify patients ≥50 years of age with a clinical diagnosis of pertussis during 2015-2019. Pertussis incidence rates ranged from 57.6 to 91.4 per 100,000 persons and were higher among women and highest in those 50-64 years of age. Patients with COPD or asthma had higher incidence rates and an increased risk for pertussis compared with the overall population ≥50 years of age. Our findings suggest that persons ≥50 years of age in Australia with COPD or asthma have a higher incidence of and risk for pertussis diagnosis.

Genomic dissection of the microevolution of Australian epidemic Bordetella pertussis

Whooping cough (pertussis) is a highly contagious respiratory disease caused by the bacterium Bordetella pertussis. Despite high vaccine coverage, pertussis has re-emerged in many countries including Australia and caused two large epidemics in Australia since 2007. Here, we undertook a genomic and phylogeographic study of 385 Australian B. pertussis isolates collected from 2008 to 2017. The Australian B. pertussis population was found to be composed of mostly ptxP3 strains carrying different fim3 alleles, with ptxP3-fim3A genotype expanding far more than ptxP3-fim3B. Within the former, there were six co-circulating epidemic lineages (EL1 to EL6). The multiple ELs emerged, expanded, and then declined at different time points over the two epidemics. In population genetics terms, both hard and soft selective sweeps through vaccine selection pressures have determined the population dynamics of Australian B. pertussis. Relative risk estimation suggests that once a new B. pertussis lineage emerged, it was more likely to spread locally within the first 1.5 years. However, after 1.5 years, any new lineage was likely to expand to a wider region. Phylogenetic analysis revealed the expansion of ptxP3 strains was also associated with replacement of the type III secretion system allele bscI1 with bscI3. bscI3 is associated with decreased T3SS secretion and may allow B. pertussis to reduce immune recognition. This study advanced our understanding of the epidemic population structure and spatial and temporal dynamics of B. pertussis in a highly immunized population.

ARIMA and ARIMA-ERNN models for prediction of pertussis incidence in mainland China from 2004 to 2021

Objective

To compare an autoregressive integrated moving average (ARIMA) model with a model that combines ARIMA with the Elman recurrent neural network (ARIMA-ERNN) in predicting the incidence of pertussis in mainland China.

Background

The incidence of pertussis has increased rapidly in mainland China since 2016, making the disease an increasing public health threat. There is a pressing need for models capable of accurately predicting the incidence of pertussis in order to guide prevention and control measures. We developed and compared two models for predicting pertussis incidence in mainland China.

Methods

Data on the incidence of pertussis in mainland China from 2004 to 2019 were obtained from the official website of the Chinese Center for Disease Control and Prevention. An ARIMA model was established using SAS (ver. 9.4) software and an ARIMA-ERNN model was established using MATLAB (ver. R2019a) software. The performances of these models were compared.

Results

From 2004 to 2019, there were 104,837 reported cases of pertussis in mainland China, with an increasing incidence over time. The incidence of pertussis showed obvious seasonal characteristics, with the peak lasting from March to September every year. Compared with the mean squared error (MSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) of the ARIMA model, those of the ARIMA-ERNN model were 81.43%, 95.97% and 80.86% lower, respectively, in fitting performance. In terms of prediction performance, the MAE, MSE and MAPE were 37.75%, 56.88% and 43.75% lower, respectively.

Conclusion

The fitting and prediction performances of the ARIMA-ERNN model were better than those of the ARIMA model. This provides theoretical support for the prediction of infectious diseases and should be beneficial to public health decision making.

Pertussis surveillance results from a French general practitioner network, France, 2017 to 2020

Introduction

In France, three complementary surveillance networks involving hospitals and paediatrician practices currently allow pertussis surveillance among infants (<1 year old) and children (1–12 years old). Data on incidences among adolescents (13–17 years old) and adults (≥ 18 years) are scarce. In 2017, a sentinel surveillance system called Sentinelles network, was implemented among general practitioners (GPs).

Aim

The purpose of Sentinelles network is to assess pertussis incidence, monitor the cases’ age distribution and evaluate the impact of the country’s vaccination policy. We present the results from the first 4 years of this surveillance.

Methods

GPs of the French Sentinelles network reported weekly numbers of epidemiologically or laboratory-confirmed cases and their characteristics.

Results

A total of 132 cases were reported over 2017–2020. Estimated national incidence rates per 100,000 inhabitants were 17 (95% confidence interval (CI): 12–22) in 2017, 10 (95% CI: 6–14) in 2018, 15 (95% CI: 10–20) in 2019 and three (95% CI: 1–5) in 2020. The incidence rate was significantly lower in 2020 than in 2017–2019. Women were significantly more affected than men (83/132; 63% of women, p = 0.004); 66% (87/132) of cases were aged 15 years or over (median age: 31.5 years; range: 2 months–87 years). Among 37 vaccinated cases with data, 33 had received the recommended number of doses for their age.

Conclusions

These results concur with incidences reported in other European countries, and with studies showing that the incidences of several respiratory diseases decreased in 2020 during the COVID-19 pandemic. The results also suggest a shift of morbidity towards older age groups, and a rapid waning of immunity after vaccination, justifying to continue this surveillance.

Estimating pertussis incidence in general practice using a large Australian primary care database

BACKGROUND

While pertussis is notifiable in most countries, notifications typically underestimate the true pertussis burden. We explored the incidence of pertussis in general practice in Australia.

METHODS

Using MedicineInsight, a large longitudinal electronic medical record database of general practice (primary care) encounters which includes >1.5 million patients, we first defined a cohort of active patients and then used free-text search algorithms to identify patients with pertussis-related encounters. We defined and identified pertussis-related encounters in four patient categories: pertussis-associated (category 1), potential pertussis (category 2), epidemiologically-linked pertussis (category 3), and symptoms consistent with pertussis (category 4). Incident pertussis-related encounter rates per 100,000 active patients were calculated from Jan 2008 to Aug 2015.

RESULTS

Estimated mean annual pertussis incidence increased as definitions were expanded, from 94.3 (category 1 patients only) to 148.8 (categories 1+2+3 patients combined) per 100,000 active patients per year. Monthly time-series corresponding to the first three categories were highly correlated (Pearson's r > 90% for each pair), but each was poorly correlated with category 4. For categories 1+2+3, the highest incidence was among 0-4 and 5-9 year olds. Incidence was 30% higher in females than males (i.e. 184.5 vs 139.8 per 100,00 active patients for categories 1-3 patients combined). Pertussis-associated incidence (category 1) was similar to national pertussis notification rates. Categories 2 and 3 added 25% and 33%, respectively, on average relative to category 1 incidence. The estimated incidence from categories 1+2+3 together were on average 64% higher than national pertussis notification rates.

CONCLUSION

We provide comprehensive estimates of pertussis-related incidence in general practice (primary care), well in excess of notified pertussis incidence in Australia. This highlights the utility of MedicineInsight data in providing a greater understanding of the burden of medically-attended pertussis infections.

Retrospective analysis of bacterial culture-confirmed pertussis cases in Beijing Children's hospital from 2014 to 2019 reveals prevention and control of the grim situation in mainland China

BACKGROUND

Our study aims to explore the epidemiological features of children with bacterial culture-confirmed pertussis visiting Beijing Children's Hospital, China.

METHODS

From 2014 through 2019, patients with suspected pertussis coming from mainland China provided nasopharyngeal swabs and bacterial culture that was subsequently cultivated.

RESULTS

During the study period, 6956 children with suspected pertussis from 30 different administrative provinces of mainland China were investigated, of which 1494 cases (21.5%) had positive B. pertussis culture. The number of pertussis cases increased year-on-year, from 122 in 2014 to 279 in 2019. Of the confirmed cases, 38.2% and 26.8% were identified in the summer and autumn, respectively. The age distribution of children with pertussis showed that 77.2% were <12 months old, including 56.0% <6 months old. Only thirteen B. parapertussis isolates and one B. bronchiseptica isolates were collected in the present samples.

CONCLUSIONS

The present culture-confirmed cases reveal the severe epidemic situation of pertussis spreading over the whole country and mainly affecting the infants. It is necessary to set up hospital-based surveillance with reliable laboratory methods to promote clinical awareness and to monitor the disease.

Association of weather variability with resurging pertussis infections among different age groups: A non-linear approach

Pertussis has resurged in many countries over recent years, especially among adolescents and adults. This study assessed the effect of weather variability on resurging pertussis among different age groups in Jinan, China. Data on weekly pertussis notifications by age group and weather factors (mean temperature (MeanT), mean temperature standard deviation within a week (MeanT SD), diurnal temperature range (DTR) and relative humidity (RH)) were collected between 2013 and 2017. Distributed lag non-linear models (DLNMs) and regression tree models were used to examine the non-linear association between weather variability and pertussis infections. The 2-weeks cumulative relative risk (RR) of pertussis infections was 4.46 (95% confidence interval (CI): 2.33-9.51) in 0-4 age group, 6.25 (95% CI: 1.38-22.76) in 5-9 age group and 10.11 (95% CI: 2.83-39.07) in 10+ age group when MeanT was at 30.0 °C. MeanT SD (RR range in the three age groups: 2.82-5.83), DTR (RR range: 6.33-11.56) and RH (RR range: 2.02-7.43) also exert significant influence, with the highest risks at 10+ age group. Regression tree models showed the interactive effects of weather variability. The mean pertussis infections increased by over 1.7-fold in 0-4 years group when MeanT ≥14 °C, RH ≥57% and DTR ≥10 °C; by over 2.3-fold in 5-9 years group when MeanT ≥20 °C and MeanT SD ≥3 °C; by 2.0-fold in 10+ years group when MeanT ≥0.7 °C, DTR ≥8.3 °C and RH ≥74%. The study found significantly different associations between weather variability and pertussis infections by age group, and appeared to be stronger in 10+ years group. Continuing climate change, together with other risk factors such as low antibody levels among adolescents and adults, may facilitate pertussis resurgence. This supports previous suggestions of carefully reconsidering current vaccination programme to effectively curb the resurgence of pertussis.

High healthcare resource utilisation due to pertussis in Australian adults aged 65 years and over

BACKGROUND

In the context of co-morbid illness and increasing age, data on excess morbidity from pertussis in older adults is crucial for immunisation policy but has been largely limited to case-series.

METHODS

We designed a matched case-control study nested within a population-based cohort of 267,153 adults aged ≥45 years in New South Wales, Australia (The 45 and Up Study cohort). Excess hospital bed days, emergency department (ED) admissions, general practitioner (GP) visits, and prescriptions were estimated using negative binomial regression models. An additional self-controlled analysis was also conducted to validate the main models, and to evaluate results for those with either asthma or a body mass index (BMI)≥30 compared to those without these risk factors.

RESULTS

Based on 524 pairs of PCR-confirmed pertussis cases and matched controls, we estimated an excess healthcare utilisation per case of 2.5 prescriptions (95% CI: 0.2-4.7), of which 1.1 (95% CI: 0.5-2.2) were antibiotics, 2.3 GP visits (95% CI: 2.0-2.6), and 0.1 ED admissions (95% CI: 0.1-0.2). Compared to those 45-64 years, cases ≥65 years had a significantly greater excess for all prescriptions (1.1 vs 4.7/case), antibiotic prescriptions (0.1 vs 2.2/case), and ED admissions (0.1 vs 0.2/case), but no significant excess of respiratory-related hospital bed days. An additional self-controlled analysis confirmed that cases with either asthma or BMI≥30 had higher overall healthcare utilisation but this was not associated with pertussis infection.

CONCLUSION

We found a substantial excess outpatient healthcare burden among adults aged 65 years and over with PCR-confirmed pertussis, supporting further evaluation of preventive measures.