The temporal pattern and relationship of Campylobacter prevalence in broiler slaughter batches and human campylobacteriosis cases in Sweden 2009-2019.

Thermophilic Campylobacter species are the most common cause of bacterial gastroenteritis worldwide, and handling and consumption of broiler meat is considered a major foodborne transmission route. Both the incidence of campylobacteriosis and the prevalence of Campylobacter in broilers show seasonality but the impact of this association and broiler prevalence on human incidence is not clear. To explore this relationship we applied two approaches for analyzing time series data using different time resolutions (weekly, bi-weekly or monthly data) of human campylobacteriosis cases and prevalence of Campylobacter spp. in broiler slaughter batches in Sweden between 2009 and 2019. The decomposition of time series into seasonal (S), long-term trend (T) and residual components (STL model) showed a close overlap in seasonal patterns in terms of timing and the proportional change of peaks from normalized yearly levels. Starting 2016, when a large outbreak was reported, there was significant overlap in the trend components as well. The trend component of human cases prior to the outbreak corresponded to a linear increase of 6.5 % cases annually. In comparison, the estimated annual increase in broiler consumption was 2.7 %. An additive approach for time-series counts incorporating seasonal and epidemic (cases are a function of previous cases) components found a positive association between human cases and broiler prevalence with an optimal lag of 2 weeks, 1 bi-week, or 0 months. Considering the estimated time between slaughter and consumption, incubation time, and the time between on-set of disease and testing, a 2-week lag may be consistent with transmission via handling and consumption of fresh broiler meat. The best model included broiler prevalence as a factor in the epidemic model component, not in the seasonal component. The outcomes in terms of best model, optimal lags and significance of parameters, using weekly, bi-weekly or monthly data were, in general, in agreement but varied with data resolution when only a subset of the time series, not including any known broiler associated outbreaks, was analyzed. The optimal resolution based on the available data and conditions of the present analysis appeared to be weekly or bi-weekly data. Results suggest that broiler prevalence with a 2 week lag period can explain part of the human cases but has a smaller explanatory impact during the part of the study period not including the large known outbreaks. There is no simple relationship between broiler prevalence and human cases. Additional factors than broiler prevalence need to be evaluated in order to understand the transmission routes and epidemiology of campylobacteriosis.

Investigating the Campylobacter enteritis winter peak in Germany, 2018/2019.

Surveillance of notified Campylobacter enteritis in Germany revealed a recurrent annual increase of cases with disease onset several days after the Christmas and New Year holidays ("winter peak"). We suspected that handling and consumption of chicken meat during fondue and raclette grill meals on the holidays were associated with winter peak Campylobacter infections. The hypothesis was investigated in a case-control study with a case-case design where notified Campylobacter enteritis cases served as case-patients as well as control-patients, depending on their date of disease onset (case-patients: 25/12/2018 to 08/01/2019; control-patients: any other date between 30/11/2018 and 28/02/2019). The study was conducted as an online survey from 21/01/2019 to 18/03/2019. Adjusted odds ratios (aOR) were determined in single-variable logistic regression analyses adjusted for age group and sex. We analysed 182 data sets from case-patients and 260 from control-patients and found associations of Campylobacter infections after the holidays with meat fondue (aOR 2.2; 95% confidence interval (CI) 1.2-3.8) and raclette grill meals with meat (aOR 1.5; 95% CI 1.0-2.4) consumed on the holidays. The associations were stronger when chicken meat was served at these meals (fondue with chicken meat: aOR 2.7; 95% CI 1.4-5.5; raclette grill meal with chicken meat: aOR 2.3; 95% CI 1.3-4.1). The results confirmed our initial hypothesis. To prevent Campylobacter winter peak cases in the future, consumers should be made more aware of the risks of a Campylobacter infection when handling raw meat, in particular chicken, during fondue or raclette grill meals on the holidays.

Differential impact of the COVID-19 pandemic on laboratory reporting of norovirus and Campylobacter in England: A modelling approach.

BACKGROUND: The COVID-19 pandemic has impacted surveillance activities for multiple pathogens. Since March 2020, there was a decline in the number of reports of norovirus and Campylobacter recorded by England's national laboratory surveillance system. The aim is to estimate and compare the impact of the COVID-19 pandemic on norovirus and Campylobacter surveillance data in England. METHODS: We utilised two quasi-experimental approaches based on a generalised linear model for sequential count data. The first approach estimates overall impact and the second approach focuses on the impact of specific elements of the pandemic response (COVID-19 diagnostic testing and control measures). The following time series (27, 2015-43, 2020) were used: weekly laboratory-confirmed norovirus and Campylobacter reports, air temperature, conducted Sars-CoV-2 tests and Index of COVID-19 control measures stringency. RESULTS: The period of Sars-CoV-2 emergence and subsequent sustained transmission was associated with persistent reductions in norovirus laboratory reports (p = 0.001), whereas the reductions were more pronounced during pandemic emergence and later recovered for Campylobacter (p = 0.075). The total estimated reduction was 47% - 79% for norovirus (12-43, 2020). The total reduction varied by time for Campylobacter, e.g. 19% - 33% in April, 1% - 7% in August. CONCLUSION: Laboratory reporting of norovirus was more adversely impacted than Campylobacter by the COVID-19 pandemic. This may be partially explained by a comparatively stronger effect of behavioural interventions on norovirus transmission and a relatively greater reduction in norovirus testing capacity. Our study underlines the differential impact a pandemic may have on surveillance of gastrointestinal infectious diseases.