A multidisciplinary and structured investigation of three suspected clusters of transverse upper limb reduction defects in France.

INTRODUCTION: Between 2019-2021, facing public concern, a scientific expert committee (SEC) reanalysed suspected clusters of transverse upper limb reduction defects (TULRD) in three administrative areas in France, where initial investigations had not identified any risk exposure. We share here the national approach we developed for managing suspicious clusters of the same group of congenital anomalies occurring in several areas. METHODS: The SEC analysed the medical records of TURLD suspected cases and performed spatiotemporal analyses on confirmed cases. If the cluster was statistically significant and included at least three cases, the SEC reviewed exposures obtained from questionnaires, environmental databases, and a survey among farmers living near to cases' homes concerning their plant product use. RESULTS: After case re-ascertainment, no statistically significant cluster was observed in the first administrative areas. In the second area, a cluster of four children born in two nearby towns over two years was confirmed, but as with the initial investigations, no exposure to a known risk factor explaining the number of cases in excess was identified. In the third area, a cluster including just two cases born the same year in the same town was confirmed. DISCUSSION: Our experience highlights that in the event of suspicious clusters occurring in different areas of a country, a coordinated and standardised approach should be preferred.

The state of integrated disease surveillance globally: synthesis report of a mixed methods study.

OBJECTIVES: Disease surveillance is an essential public health function needed to prevent, detect, monitor and respond to health threats. Integrated disease surveillance (IDS) enhances its utility and has been advocated for decades by the World Health Organization. This study sought to examine the state of IDS implementation worldwide. STUDY DESIGN: The study used a concurrent mixed methods approach consisting of a systematic scoping review of the literature on IDS, a survey of International Association of National Public Health Institutes (IANPHI) members and qualitative deep dive case studies in seven countries. METHODS: This report collates, analyses and synthesises the findings from the three components. The scoping review consisted of a review of summarised evidence on IDS. Eight reviews and five primary studies were included. The cross-sectional survey was conducted of 110 IANPHI members representing ninety-five countries. Qualitative case studies were conducted in Malawi, Mozambique, Uganda, Pakistan, Canada, Sweden, and England, which involved thirty-four focus group discussions and forty-eight key informant interviews. RESULTS: In the different countries, IDS is conceptualised differently and there are differing levels of maturity of IDS functions. Although the role of National Public Health Institutes has not been well defined in the IDS, they play a significant role in IDS in many countries. Fragmentation between sectors and resourcing (human and financial) issues were common. Good governance measures such as appropriate legislative and regulatory frameworks and roles and responsibilities for IDS were often unclear. The COVID-19 pandemic has strengthened some surveillance systems, often through leveraging existing respiratory surveillance systems. In some instances, improvements were seen only for COVID-19 related data but these changes were not sustained. Evaluation of IDS was also reported to be weak. CONCLUSIONS: Integration should be driven by a clear purpose and contextualised. Political commitment, clear governance, and resourcing are needed. Technology and the establishment of technical communities of practice may help. However, the complexity and cost of integration should not be under-estimated, and further economic and impact evaluations of IDS are needed.

Seroprevalence for Borrelia burgdorferi sensu lato and tick-borne encephalitis virus antibodies and associated risk factors among forestry workers in northern France, 2019 to 2020.

BackgroundLyme borreliosis (LB) is the most common tick-borne disease (TBD) in France. Forestry workers are at high risk of TBD because of frequent exposure to tick bites.AimWe aimed to estimate the seroprevalence of Borrelia burgdorferi sensu lato and tick-borne encephalitis virus (TBEV) antibodies among forestry workers in northern France. We compared seroprevalence by geographical area and assessed factors associated with seropositivity.MethodsBetween 2019 and 2020, we conducted a randomised cross-sectional seroprevalence survey. Borrelia burgdorferi sl seropositivity was defined as positive ELISA and positive or equivocal result in western blot. Seropositivity for TBEV was defined as positive result from two ELISA tests, confirmed by serum neutralisation. We calculated weighted seroprevalence and adjusted prevalence ratios to determine association between potential risk factors and seropositivity.ResultsA total of 1,778 forestry workers participated. Seroprevalence for B. burgdorferi sl was 15.5% (95% confidence interval (CI): 13.9-17.3), 3.5 times higher in the eastern regions than in the western and increased with seniority and with weekly time in a forest environment. Seroprevalence was 2.5 times higher in forestry workers reporting a tick bite during past years and reporting usually not removing ticks rapidly. Seroprevalence for TBEV was 0.14% (95% CI: 0.05-0.42).ConclusionWe assessed for the first time seroprevalence of B. burgdorferi sl and TBEV antibodies among forestry workers in northern France. These results will be used, together with data on LB and tick-borne encephalitis (TBE) incidence and on exposure to tick-bites, to target prevention programmes.

Evidence of early circulation of SARS-CoV-2 in France: findings from the population-based "CONSTANCES" cohort.

Using serum samples routinely collected in 9144 adults from a French general population-based cohort, we identified 353 participants with a positive anti-SARS-CoV-2 IgG test, among whom 13 were sampled between November 2019 and January 2020 and were confirmed by neutralizing antibodies testing. Investigations in 11 of these participants revealed experience of symptoms possibly related to a SARS-CoV-2 infection or situations at risk of potential SARS-CoV-2 exposure. This suggests early circulation of SARS-CoV-2 in Europe.

Increased awareness and knowledge of Lyme Borreliosis and tick bite prevention among the general population in France: 2016 and 2019 health barometer survey.

BACKGROUND: Lyme borreliosis (LB) is the most frequent tick-borne disease in France. In the absence of a vaccine, LB prevention mainly relies on reducing tick bites. In 2016, the French Ministry of Health launched a national plan against tick-borne infections, including a prevention component. To evaluate the impact of this prevention strategy, we assessed knowledge and practices of tick bite prevention using the 2016 and 2019 national surveys on health attitudes and beliefs known as the French Health Barometer. METHODS: The Health Barometer is a repeated nationwide phone survey conducted annually on a random sample aged 18 to 75 years living in mainland France. In 2016 and 2019, participants were asked, among others, about their exposure to ticks, their behavior and practices regarding tick bites, and their knowledge about LB and its prevention. RESULTS: In 2019, 30% of the population reported a lifetime tick bite and 6% in the last year, an increase from 25% and 4%, respectively, in 2016 (p < 0.001). In 2019, 25% of the population felt exposed to tick bites compared to 23% in 2016 (p < 0.001). The proportion of participants who had heard about LB and who considered themselves well informed respectively increased from 66% and 29% in 2016 to 79% and 41% in 2019, (p < 0.001). In 2019 compared to 2016, a greater part of the French population applied protective measures against tick bites, particularly wearing protective clothing (74% vs 66%, p < 0.001) and regular tick checks and prompt tick removal after exposure (54% vs 47%, p < 0.001). CONCLUSIONS: A substantial proportion of French residents are exposed to tick bites and apply protective measures. Our findings indicate a trend toward an increased knowledge and awareness of tick bites and LB between 2016 and 2019 in France. Our results can be used to target future information campaigns to specific age groups or at-risk areas in addition to the general population. However, we need to further study the barriers to the use of preventive measures.

COVID-19 hotspots through clusters analysis in France (may-October 2020): where should we track the virus to mitigate the spread?

BACKGROUND: In France, the lifting of the lockdown implemented to control the COVID-19 first wave in 2020 was followed by a reinforced contact-tracing (CT) strategy for the early detection of cases and transmission chains. We developed a reporting system of clusters defined as at least three COVID-19 cases, within seven days and belonging to the same community or having participated in the same gathering, whether they know each other or not. The aim of this study was to describe the typology and criticality of clusters reported between the two lockdowns in France to guide future action prioritisation. METHODS: In this study we describe the typology and criticality of COVID-19 clusters between the two lockdowns implemented in France (between May and end of October 2020). Clusters were registered in a national database named "MONIC" (MONItoring des Clusters), established in May 2020. This surveillance system identified the most affected communities in a timely manner. A level of criticality was defined for each cluster to take into consideration the risk of spreading within and outside the community of occurrence, and the health impact within the community. We compared the level of criticality according to the type of community in which the cluster occurred using Pearson's chi-square tests. RESULTS: A total of 7236 clusters were reported over the study period, particularly in occupational environment (25.1%, n = 1813), elderly care structures (21.9%, n = 1586), and educational establishments (15.9%, n = 1154). We show a shift over time of the most affected communities in terms of number of clusters. Clusters reported in occupational environment and the personal sphere had increased during summer while clusters reported in educational environment increased after the start of the school year. This trend mirrors change of transmission pattern overtime according to social contacts. Among all reported clusters, 43.1% had a high level of criticality with significant differences between communities (p < 0.0001). A majority of clusters had a high level of criticality in elderly care structures (82.2%), in disability care centres (56.6%), and health care facilities (51.7%). CONCLUSION: These results highlight the importance of targeting public health action based on timely sustained investigations, testing capacity and targeted awareness campaigns. The emergence of new SARS-CoV-2 variants strengthen these public health recommendations and the need for rapid and prioritise vaccination campaigns.

Early assessment of the impact of mitigation measures to control COVID-19 in 22 French metropolitan areas, October to November 2020.

In France, measures including curfew and lockdown were implemented to control the COVID-19 pandemic second wave in 2020. This study descriptively assesses their possible effects, also relative to their timing. A considerable decrease in incidence of COVID-19 cases and hospital admissions was observed 7 to 10 days after mitigation measures were put in place, occurring earlier in metropolitan areas which had implemented these first. This temporal coincidence suggests the measures' positive impact, consistent with international experiences.

Extension of French vaccination mandates: from the recommendation of the Steering Committee of the Citizen Consultation on Vaccination to the law.

On 4 December 2017, French parliamentarians passed a law extending the vaccination mandates for children up to 2 years of age from three vaccinations (against diphtheria, tetanus and poliomyelitis) to 11 by adding vaccinations against pertussis, Haemophilus influenza b (Hib), hepatitis B, pneumococcal diseases, meningococcal C diseases, measles, mumps and rubella. This vote follows a recommendation made by the Steering Committee of the Citizen Consultation on Vaccination that took place in 2016. The law applies to all children born after 1 January 2018. Parents who do not fulfil the mandate will not be fined but non-vaccinated children will not be admitted to any collective child services such as nurseries or schools. No exemption other than for medical reasons will be considered. Here we describe the historical background of this evolution and its main epidemiological, sociological and policy drivers. They mainly refer to insufficient vaccine coverage, persistence of a preventable burden for some diseases and growing vaccine hesitancy in the French population. We also discuss some of the challenges and conditions of success.

Association between maternal prepregnancy obesity and breastfeeding duration: Data from a nationwide prospective birth cohort.

Association of maternal obesity with shorter breastfeeding duration may involve different factors and might be modified by parity. In a national birth cohort, we aimed to estimate the association between prepregnancy body mass index (pBMI) and breastfeeding duration after adjustment for sociodemographic, pregnancy, and other characteristics and assess the effect modification of parity in such associations. In 2012, 3,368 mother-infant dyads were randomly included at birth in the French Epifane cohort. Breastfeeding information was collected in maternity wards and by phone interview at 1, 4, 8, and 12 months postpartum. Poisson regression analyses estimated the association of pBMI with the number of days of "any breastfeeding" (ABF) and "exclusive breastfeeding" (EBF) in unadjusted and adjusted models. Interactions between parity and pBMI were tested. Obesity before pregnancy was independently associated with shorter ABF duration (incidence rate ratio [IRR] = 0.86, 95%CI [0.74, 0.99]) compared to normal-weight status. Parity showed an effect modification only with EBF duration. Among primiparae, no association was found for obesity, but overweight was significantly associated with shorter EBF duration independently of all covariates (IRR = 0.74 [0.58, 0.95]). Among multiparas, obesity was associated with shorter EBF duration after controlling for sociodemographic factors (IRR = 0.71 [0.53, 0.95]). This association was no longer statistically significant after controlling for other covariates. Obesity appears to be a strong risk factor in shorter ABF duration. Furthermore, parity is a key factor in the relationship of pBMI to shorter EBF duration. Overweight primiparous and obese multiparous women need additional support to prolong breastfeeding duration.

Estimated Annual Numbers of Foodborne Pathogen-Associated Illnesses, Hospitalizations, and Deaths, France, 2008-2013.

Estimates of the annual numbers of foodborne illnesses and associated hospitalizations and deaths are needed to set priorities for surveillance, prevention, and control strategies. The objective of this study was to determine such estimates for 2008-2013 in France. We considered 15 major foodborne pathogens (10 bacteria, 3 viruses, and 2 parasites) and estimated that each year, the pathogens accounted for 1.28-2.23 million illnesses, 16,500-20,800 hospitalizations, and 250 deaths. Campylobacter spp., nontyphoidal Salmonella spp., and norovirus accounted for >70% of all foodborne pathogen-associated illnesses and hospitalizations; nontyphoidal Salmonella spp. and Listeria monocytogenes were the main causes of foodborne pathogen-associated deaths; and hepatitis E virus appeared to be a previously unrecognized foodborne pathogen causing ≈68,000 illnesses in France every year. The substantial annual numbers of foodborne illnesses and associated hospitalizations and deaths in France highlight the need for food-safety policymakers to prioritize foodborne disease prevention and control strategies.

Sociodemographic factors and pregnancy outcomes associated with prepregnancy obesity: effect modification of parity in the nationwide Epifane birth-cohort.

BACKGROUND: In light of the adverse outcomes for mothers and offspring related to maternal obesity, identification of subgroups of women at risk of prepregnancy obesity and its related-adverse issues is crucial for optimizing antenatal care. We aimed to identify sociodemographic factors and maternal and neonatal outcomes associated with prepregnancy obesity, and we tested the effect modification of parity on these associations. METHODS: In 2012, 3368 mothers who had delivered in 136 randomly selected maternity wards were included just after birth in the French birth cohort, Epifane. Maternal height and weight before and at the last month of pregnancy were self-reported. Maternal and neonatal outcomes were collected in medical records. Prepregnancy Body Mass Index (pBMI) was classified into underweight (<18.5), normal (18.5-24.9), overweight (25.0-29.9) and obesity (≥30.0). Since we found statistically significant interactions with parity, the multinomial logistic regression model estimating associations of pBMI class with sociodemographic characteristics and pregnancy outcomes was stratified on parity (1335 primiparous and 1814 multiparous). RESULTS: Before pregnancy, 7.6% of women were underweight, 64.2% were of normal weight, 18.0% were overweight and 10.2% were obese. Among the primiparous, maternal age of 25-29 years (OR = 2.09 [1.13-3.87]; vs. 30-34 years), high school level (OR = 2.22 [1.33-3.73]; vs. university level), gestational diabetes (OR = 2.80 [1.56-5.01]) and hypertensive complications (OR = 3.80 [1.83-7.89]) were independently associated with prepregnancy obesity. Among the multiparous, primary (OR = 6.30 [2.40-16.57]), junior high (OR = 2.89 [1.81-4.64]) and high school (OR = 1.86 [1.18-2.93]) education levels (vs. university level), no attendance at antenatal classes (OR = 1.77 [1.16-2.72]), excess gestational weight gain (OR = 1.82 [1.20-2.76]), gestational diabetes (OR =5.16 [3.15-8.46]), hypertensive complications (OR = 8.13 [3.97-16.64]), caesarean delivery (OR = 1.80 [1.18-2.77]) and infant birth weight ≥ 4 kg (OR = 1.70 [1.03-2.80]; vs. birth weight between 2.5 kg and 4 kg) were independently associated with prepregnancy obesity. CONCLUSION: Obesity before pregnancy is associated with a set of sociodemographic characteristics and adverse pregnancy outcomes that differ across parity groups. Such findings are useful for targeted health policies aimed at attaining healthy prepregnancy weight and organizing perinatal care.

[Horizon scanning in preparation for future health threats: a pilot exercise conducted by the French Institute for Public Health Surveillance in 2014]. / La veille prospective, une démarche de préparation aux futures menaces de la santé publique : exercice mené à l'Institut de veille sanitaire en 2014.

Background: Health surveillance is a reactive process, with no real hindsight for dealing with signals and alerts. It may fail to detect more radical changes with a major medium-term or long-term impact on public health. To increase proactivity, the French Institute for Public Health Surveillance has opted for a prospective monitoring approach.Methods: Several steps were necessary: 1) Identification of public health determinants. 2) Identification of key variables based on a combination of determinants. Variables were classified into three groups (health event trigger factors, dissemination factors and response factors) and were submitted to future development assumptions. 3) Identification, in each of the three groups, of micro-scenarios derived from variable trends. 4) Identification of macro-scenarios, each built from the three micro-scenarios for each of the three groups. 5) Identification of issues for the future of public health.Results: The exercise identified 22 key variables, 17 micro-scenarios and 5 macro-scenarios. The topics retained relate to issues on social and territorial health inequalities, health burden, individual and collective responsibilities in terms of health, ethical aspects, emerging phenomena, 'Big data', data mining, new health technologies, interlocking of analysis scales.Conclusions: The approach presented here guides the programming of activities of a health safety agency, particularly for monitoring and surveillance. By describing possible future scenarios, health surveillance can help decision-makers to influence the context towards one or more favourable futures.

Global HIV epidemiology: specific patterns of the epidemic in the North and South.

Thirty years after the identification of the first cases of AIDS, it was estimated that 34 million of people were living with HIV worldwide in 2011. The incidence is declining but remains high, with 2.5 million of new HIV infections per year. Africa is the region of the world most heavily affected, accounting for three-quarters of the global burden of HIV infection and the same proportion for new infections. The incidence declines in most parts of the world while heterosexual transmission remains the dominant mode of HIV acquisition followed by homosexual transmission. Intravenous drug use continues to drive the epidemic in Eastern Europe and parts of Asia. Condom use remains the cornerstone of prevention of sexual transmission. Male medical circumcision has now been proven an effective public health intervention to prevent sexual transmission. Antiretroviral treatment may reduce sexual transmission at population level while improving the conditions of life and survival of those harbouring the virus. Harm-reduction together with blood safety prevent blood transmission. The prevention of mother-to-child transmission is now moving its global objective to elimination by the end of 2015. At least 20 years will be necessary for achieving HIV control at the worldwide level with currently available interventions.

Impact of hepatitis C triple therapy availability upon the number of patients to be treated and associated costs in France: a model-based analysis.

OBJECTIVE: The combination of pegylated interferon (PEG-IFN), ribavirin (RBV) and a protease inhibitor (PI) has been approved in summer 2011 for the treatment of genotype 1 (G1) hepatitis C virus (HCV)-infected patients, with a substantially improved efficacy. The aim of this study was to estimate the number of G1 patients to be treated in France in 2012 and associated costs. METHODS: A published model of HCV and data on PEG-IFN sales were used to estimate patients needing treatment using three scenarios. (1) HCV screening rate unchanged versus 2010; proportion of treated F0-F1 patients unchanged, proportion of treated F2-F4 patients increased to the current proportion of treated F2-F4 G2/3 patients. (2) Scenario 1 but the proportion of treated F0-F1 patients increased to the current proportion of treated F0-F1 G2/3 patients. (3) Scenario 2 but a 5% increase in the HCV screening rate. To estimate cost, treatment duration was multiplied by drug unit cost. Probabilities corresponding to treatment duration were estimated based on liver fibrosis stage, treatment-naive or experienced status of the patient and virological response kinetics on treatment. RESULTS: Compared with the 5100 G1 patients treated in 2010, the number of G1 patients receiving treatment in 2012 would be 15,000 in scenario 1, 18,300 in scenario 2 and 19,400 in scenario 3, among whom 2.5-3.7% may receive PEG-IFN/RBV and 96.3-97.5% PEG-IFN/RBV+PI. Costs associated with this regimen use ranged from 497 to 638 million Euros. CONCLUSION: These model-based estimates indicate that new anti-HCV treatments may result in a three- to fourfold increase in the number of G1 patients to be treated in France in 2012.

Incidence of listeriosis and related mortality among groups at risk of acquiring listeriosis.

BACKGROUND: Listeriosis is a foodborne disease of significant public health concern that primarily affects persons with recognized underlying conditions or diseases that impair cell-mediated immunity. The degree of risk posed by the different underlying conditions is crucial to prioritize prevention programs that target the highest risk populations. METHODS: We reviewed cases of listeriosis reported in France from 2001 to 2008. Numbers of cases and deaths were tabulated by age and underlying condition. Measures of the impact of specific underlying conditions on the occurrence of listeriosis were calculated. For estimating the total number of persons living with specific diseases, we applied prevalence estimates of these diseases to the French population. Underlying conditions were ranked by the degree to which they increased the risk of listeriosis. RESULTS: From 2001 to 2008, 1959 cases of listeriosis were reported in France (mean annual incidence 0.39 per 100,000 residents). Compared with persons <65 years with no underlying conditions, those with chronic lymphocytic leukemia had a >1000-fold increased risk of acquiring listeriosis, and those with liver cancer; myeoloproliferative disorder; multiple myeloma; acute leukemia; giant cell arteritis; dialysis; esophageal, stomach, pancreas, lung, and brain cancer; cirrhosis; organ transplantation; and pregnancy had a 100-1000-fold increased risk of listeriosis. CONCLUSIONS: To be effective and acceptable to physicians and patients, listeriosis prevention strategies should be targeted based on evidence of increased risk. Stringent dietary guidance, to avoid specific foods with a high risk for Listeria contamination, should be targeted to pregnant women and to others at highest risk of listeriosis.

Practical considerations for sensitivity analysis after multiple imputation applied to epidemiological studies with incomplete data.

BACKGROUND: Multiple Imputation as usually implemented assumes that data are Missing At Random (MAR), meaning that the underlying missing data mechanism, given the observed data, is independent of the unobserved data. To explore the sensitivity of the inferences to departures from the MAR assumption, we applied the method proposed by Carpenter et al. (2007).This approach aims to approximate inferences under a Missing Not At random (MNAR) mechanism by reweighting estimates obtained after multiple imputation where the weights depend on the assumed degree of departure from the MAR assumption. METHODS: The method is illustrated with epidemiological data from a surveillance system of hepatitis C virus (HCV) infection in France during the 2001-2007 period. The subpopulation studied included 4343 HCV infected patients who reported drug use. Risk factors for severe liver disease were assessed. After performing complete-case and multiple imputation analyses, we applied the sensitivity analysis to 3 risk factors of severe liver disease: past excessive alcohol consumption, HIV co-infection and infection with HCV genotype 3. RESULTS: In these data, the association between severe liver disease and HIV was underestimated, if given the observed data the chance of observing HIV status is high when this is positive. Inference for two other risk factors were robust to plausible local departures from the MAR assumption. CONCLUSIONS: We have demonstrated the practical utility of, and advocate, a pragmatic widely applicable approach to exploring plausible departures from the MAR assumption post multiple imputation. We have developed guidelines for applying this approach to epidemiological studies.

Methadone induction in primary care (ANRS-Methaville): a phase III randomized intervention trial.

BACKGROUND: In France, the rapid scale-up of buprenorphine, an opioid maintenance treatment (OMT), in primary care for drug users has led to an impressive reduction in HIV prevalence among injecting drug users (IDU) but has had no major effect on Hepatitis C incidence. To date, patients willing to start methadone can only do so in a methadone clinic (a medical centre for drug and alcohol dependence (CSAPA) or a hospital setting) and are referred to primary care physicians after dose stabilization. This study aims to assess the effectiveness of methadone in patients who initiated treatment in primary care compared with those who initiated it in a CSAPA, by measuring abstinence from street opioid use after one year of treatment. METHODS/DESIGN: The ANRS-Methaville study is a randomized multicenter non-inferiority control trial comparing methadone induction (lasting approximately 2 weeks) in primary care and in CSAPA. The model of care chosen for methadone induction in primary care was based on study-specific pre-training of all physicians, exclusion criteria and daily supervision of methadone during the initiation phase. Between January 2009 and January 2011, 10 sites each having one CSAPA and several primary care physicians, were identified to recruit patients to be randomized into two groups, one starting methadone in primary care (n = 147), the other in CSAPA (n = 48). The primary outcome of the study is the proportion of participants abstinent from street opioids after 1 year of treatment i.e. non-inferiority of primary care model in terms of the proportion of patients not using street opioids compared with the proportion observed in those starting methadone in a CSAPA. DISCUSSION: The ANRS-Methaville study is the first in France to use an interventional trial to improve access to OMT for drug users. Once the non-inferiority results become available, the Ministry of Health and agency for the safety of health products may change the the New Drug Application (NDA) of methadone and make methadone induction by trained primary care physicians possible.The trial is registered with the French Agency of Pharmaceutical Products (AFSSAPS) under the number 2008-A0277-48, the European Union Drug Regulating Authorities Clinical Trials.Number Eudract 2008-001338-28, the ClinicalTrials.gov Identifier: NCT00657397 and the International Standard Randomised Controlled Trial Number Register ISRCTN31125511.

Estimating chikungunya virus transmission parameters and vector control effectiveness highlights key factors to mitigate arboviral disease outbreaks.

BACKGROUND: Viruses transmitted by Aedes mosquitoes have greatly expanded their geographic range in recent decades. They are considered emerging public health threats throughout the world, including Europe. Therefore, public health authorities must be prepared by quantifying the potential magnitude of virus transmission and the effectiveness of interventions. METHODOLOGY: We developed a mathematical model with a vector-host structure for chikungunya virus transmission and estimated model parameters from epidemiological data of the two main autochthonous chikungunya virus transmission events that occurred in Southern France, in Montpellier (2014) and in Le Cannet-des-Maures (2017). We then performed simulations of the model using these estimates to forecast the magnitude of the foci of transmission as a function of the response delay and the moment of virus introduction. CONCLUSIONS: The results of the different simulations underline the relative importance of each variable and can be useful to stakeholders when designing context-based intervention strategies. The findings emphasize the importance of, and advocate for early detection of imported cases and timely biological confirmation of autochthonous cases to ensure timely vector control measures, supporting the implementation and the maintenance of sustainable surveillance systems.