Nationwide outbreak of Salmonella enterica serotype 4,12:i:- infections in France, linked to dried pork sausage, March-May 2010

In May 2010, a nationwide excess of infections with the specific monophasic variant Salmonella enterica serotype 4,12:i:- was investigated in France. Subtyping with multilocus variable number of tandem repeats analysis revealed a distinct epidemic strain within this excess. Epidemiological investigations identified a dried pork sausage sold by a particular chain of supermarkets as the likely vehicle of transmission. The suspected batches have been withdrawn and recalled.

Outbreak of Salmonella enterica serotype Muenster infections associated with goat's cheese, France, March 2008

Salmonella enterica serotype Muenster (hereafter referred to as S. Muenster) is rare in France and in Europe. In France, a nationwide outbreak of gastrointestinal illness due to S. Muenster occurred during March and April 2008. Twenty-five laboratory-confirmed cases of S. Muenster were documented by telephone using a trawling questionnaire. Four patients were admitted to hospital and no death was recorded. Among the 21 interviewed cases, 16 reported consumption of goat's cheese in the days prior to symptoms. The investigation incriminated goat's cheese from producer X as being the most likely source of the outbreak. S. Muenster was isolated from both cases and the incriminated goat's cheese. The pulsed-field gel electrophoresis profiles of the food isolates of producer X and the isolates from cases were indistinguishable. Following the withdrawal of the contaminated batch of cheese, the number of cases decreased to its usual level. To our knowledge, this is the first published outbreak of S. Muenster associated with food consumption in Europe.

Community-wide outbreak of Escherichia coli O157:H7 associated with consumption of frozen beef burgers

On 24-25 October 2005 a cluster of five haemolytic uraemic syndrome (HUS) cases was reported in southwest France. An investigation was undertaken to identify the outbreak source and implement control measures. Cases were defined as individuals with HUS or diarrhoea with isolation of Escherichia coli O157:H7 in stools or a positive antibody response to E. coli O157 lipopolysaccharide, resident in southwest France with symptom onset after 19 September 2005. Sixty-nine identified patients had symptom onset between 5 October and 3 November 2005, including 17 cases of HUS. One brand of frozen beef burgers produced on 22 August 2005 was consumed by all patients in the week before symptom onset. E. coli O157:H7 strains from patients, patients' burgers and the manufacturing plant were genetically related. This is the largest community-wide outbreak of E. coli O157:H7 in France to date and the first associated with consumption of contaminated frozen beef burgers.

[Epidemiological surveillance of Creutzfeldt-Jakob in France]

INTRODUCTION

Transmissible spongiform encephalopathies (TSE) have been under epidemiological surveillance in France and in Europe since the early 1990s. The observation of iatrogenic Creutzfeldt-Jakob disease (CJD), the outbreak of bovine spongiform encephalopathy (ESB) and its probable transmission to many species gave rise to the surveillance which remains warranted by the emergence of a variant of CJD (vCJD), in 1996.

STATE OF ART

In France, epidemiological surveillance is coordinated by the InVS which receives input from cases notifications addressed to INSERM Unit 708 directly by clinicians or more often following requests for 14-3-3 detection in CSF. All suspected cases are followed up until a final diagnosis is established. Thanks to the effectiveness of the French network of neuropathology, autopsies are performed in more than half of patients who die with a diagnosis of suspected CJD. Diagnostic criteria allow comparison of the incidence of the different forms of the disease in all countries with a system of surveillance. Sporadic CJD is the most frequent form of the disease with more than 80% of the cases. Its origin remains unknown. To date, cases of iatrogenic CJD referred to the French surveillance network have been caused by dura mater grafts or human growth hormone treatments administrated in the 1980s. Ten percent of TSE are of genetic origin with an autosomic dominant transmission of a mutation or an insertion located on the PRNP gene. The most recent form of the disease is vCJD which is a new form, first described in the United Kingdom in 1994.

PROSPECT AND CONCLUSION

Active epidemiological surveillance remains a timely issue, particularly in France, because of the development of new cases of iatrogenic CJD after human growth hormone treatment. It is of importance in France and worldwide because of the emergence of post-transfusional cases of vCJD and the possible appearance of vCJD in persons with valine-valine or methionine-valine genotypes at codon 129.

An oyster-associated hepatitis A outbreak in France in 2007

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An oyster-associated hepatitis A outbreak in France in 2007

Following the notification of nine hepatitis A cases clustered in the Cotes d Armor district in northwestern France, epidemiological, environmental and microbiological investigations were set up in order to identify the source and vehicle of contamination and implement control measures. In total, 111 cases were identified in the outbreak, all of whom lived or had stayed as tourists in the Cotes d Armor district. Of the cases, 87% had eaten raw shellfish, and 81% specifically oysters. Traceback investigations carried out on raw shellfish consumed by the cases showed that the raw shellfish originated from a single shellfish farm. The shellfish were probably contaminated either in the submersible tanks or in a depuration land-based tank where they were stored. The source of contamination was not identified but shellfish could have been tainted by sewage overflows or by wastewater releases from a polluted storm sewer close to the shellfish farm or from on-site sanitation facilities. To prevent future hepatitis A outbreaks due to shellfish consumption from this area, hazards specific to each farm should be analysed. Timely information on sewage overflows should also be part of communities efforts regarding sewage collection and treatment.

Cluster of cases of hepatitis A with a travel history to Egypt, September-November 2008, France

Since September 2008, 26 cases of hepatitis A with a history of travel to Egypt have been reported in France. Investigations indicate that a common source of contamination linked to Nile river cruises is the most likely explanation of the increase in the number of cases reported in France as well as in several other European Union countries.

Cluster of cases of hepatitis A with a travel history to Egypt, September-November 2008, France

Since September 2008, 26 cases of hepatitis A with a history of travel to Egypt have been reported in France. Investigations indicate that a common source of contamination linked to Nile river cruises is the most likely explanation of the increase in the number of cases reported in France as well as in several other European Union countries.

Encéphalites infectieuses: données et limites du PMSI pour l'étude épidémiologique, France métropolitaine 2000–2002

Many virus and bacteria can cause encephalitis but are rarely identified as the aetiological agent by individual diagnosis. In France, the only continuous source of information about encephalitis is the national hospital medical database (NHMD). Data from the VIH-negative patients recorded in mainland France between 2000 and 2002 with a diagnosis of encephalitis were extracted and analysed according to demographic, geographical and temporal distribution. Hospitalisation details were described. An average of 1200 patients was recorded each year. They were residents of all French districts and equally hospitalized in university hospitals and non university hospitals. Their mean age was 38, and most were men. The aetiological diagnosis was unknown for 80%. The most frequent aetiological diagnosis was herpes simplex virus in adults, and VZV virus in children. These results give us some clues to design a national study on encephalitis. The study will be implemented in mainland France in 2007 and will last one year. We invite all voluntary hospitals to include their encephalitic patients in our study.

[Principles of an outbreak investigation in public health practice]

An outbreak (or epidemic) is a higher number of cases of a given disease in a given population and time interval. A timely investigation has for aim to identify the source and vehicle of the outbreak and provides unique opportunities to better understand its occurrence and the role of contributing risk factors to implement the most appropriate measures to control it and prevent further recurrences. The investigation of an outbreak is based on a multidisciplinary approach (clinical, epidemiological, environmental, and microbiological) with a descriptive and analytical (hypothesis testing) phase. In this article, we describe the methodological approach of a field outbreak investigation illustrated by examples taken from our experience. The investigation includes the following steps: establishing the existence of the outbreak; defining the disease; finding cases; describing cases by time, place, and person characteristics; establishing a hypothesis related to the mode of occurrence; testing the hypotheses; conducting an environmental investigation; conducting a microbiological investigation; controlling the outbreak, preventing further occurrences, and writing an investigation report to share experience with the public health and scientific community. The investigation of an outbreak is an evolving process: information gathered or conclusions made at a given stage must be fully used for following steps. The social, institutional, and political background associated with outbreaks usually makes their investigation complex and should be taken into account. The earlier the outbreak is detected and investigated in close relation with public health authorities, the greater will be the potential preventive impact of control measures.

O148 Shiga toxin-producing Escherichia coli outbreak: microbiological investigation as a useful complement to epidemiological investigation

An outbreak of Shiga toxin-producing Escherichia coli (STEC) O148 infection occurred among wedding attendees in France in June 2002. A retrospective cohort study was performed and ten cases were identified, including two adults with haemolytic uraemic syndrome (HUS). The analytical study revealed that > 80% of affected individuals had eaten lightly roasted mutton and poultry pâté, but only the consumption of pâté tended to be associated with illness (relative risk 3.4; 95% CI 0.8-14.4). Left-overs (cooked mutton and raw offal) and processed foods (pâté) from the same batches as served at the party were sampled. Human, food and environmental samples were examined for the Shiga toxin (stx) gene and virulence traits by PCR. Stx-positive samples were cultured for STEC. HUS cases were tested for serum antibodies against 26 major STEC serogroups. An STEC O26 strain (stx1, eae, ehxA) was isolated from one case with diarrhoea, and an STEC O148 strain (stx2c) from one case of HUS. Serum antibodies against O26 were not detected in either of these patients; antibodies against O148 were not tested. Three STEC strains were isolated from the mutton and the offal (stx2c, O148), and two from the pâté (stx2c, O-X and O-Y). The isolates from the mutton were indistinguishable from the human stx2c isolate, whereas the pâté isolates differed. Although four different STEC strains were identified in patients and foods, the results of molecular subtyping, in conjunction with analysis of food consumption patterns, strongly suggested that this outbreak was caused by mutton contaminated with STEC O148.

Surveillance of human listeriosis in France, 2001-2003

Mandatory notification of listeriosis began in France in 1999. Enhanced public health surveillance, including routine molecular characterisation of Listeria monocytogenes strains, epidemiologic follow up of cases, and collection of food samples, has improved the sensitivity of outbreak detection and response.

Commercial watercress as an emerging source of fascioliasis in Northern France in 2002: results from an outbreak investigation

In April 2002, five cases of fascioliasis were diagnosed in Tourcoing. A case-finding and a case-control study were carried out to identify the source of the outbreak and take appropriate control measures. Eighteen cases were identified through the medical laboratories carrying out serology for fascioliasis. Fourteen cases and 23 controls, identified by the physicians of the cases, were interviewed on symptoms of the disease and their consumption of uncooked plants. Cases were more likely than controls to have eaten commercialized raw watercress (OR 86.7, P < 0.001) and 13 (93%) of the cases reported its consumption. A single producer common to all cases was identified. The inspection of his watercress beds showed a lack of protection against Lymnaea truncatula. This outbreak of fascioliasis due to commercialized watercress indicates that actual sanitary regulations do not allow for the efficient prevention of infestation of watercress production in France.

Escherichia coli O157 outbreak associated with fresh unpasteurized goats' cheese

A family cluster of three cases of Escherichia coli O157 infection was identified in France. Two cases developed haemolytic-uraemic syndrome. The source was fresh unpasteurized goats' cheese, produced by an independent producer. Three E. coli O157 strains, isolated from one HUS case and faeces of one cow and one goat, were indistinguishable by toxin type and PFGE pattern.

An outbreak of airborne tularaemia in France, August 2004

Fifteen tularaemia cases were identified after a holiday spent at a converted mill in the Vendee region in France, between 9 and 12 August 2004. The mill was visited, and descriptive, retrospective cohort and environmental investigations were conducted. The 39 people who had stayed at the mill between 24 July and 11 August were asked about symptoms, exposure to food and animals, and leisure activities. A case was defined as a person with evidence of fever and a positive serology (seroconversion or significant rise in antibody titre, or a single titre) = 40. Culture for Francisella tularensis and polymerase chain reaction (PCR) diagnosis was carried out for drinking water, firewood, and domestic animals at the mill. Fifteen cases of tularaemia (38%) were confirmed. Twelve of the cases (80%) had the pulmonary form. None of the patients was admitted to hospital. There was a strong association between infection and participation in a dinner at the mill on 4 August (p&lt;10-8). One of the three dogs present in the dining room was serologically positive for F. tularensis. Results of analysis of environmental samples were negative. These investigations confirmed the occurrence of a cluster of 15 tularaemia cases, in patients who were infected on the evening of 4 August, in a mill in Vend¨¦e, an endemic area for tularaemia. The investigations highlight the existence of nonspecific and benign pulmonary forms of the illness in France. The pulmonary form of infection in the human cases and the positive serology of the dog suggest contamination by inhalation of contaminated particles from the dog¡¯s fur disseminated by the dog shaking itself.

An outbreak of airborne tularaemia in France, August 2004

Fifteen tularaemia cases were identified after a holiday spent at a converted mill in the Vendee region in France, between 9 and 12 August 2004. The mill was visited, and descriptive, retrospective cohort and environmental investigations were conducted. The 39 people who had stayed at the mill between 24 July and 11 August were asked about symptoms, exposure to food and animals, and leisure activities. A case was defined as a person with evidence of fever and a positive serology (seroconversion or significant rise in antibody titre, or a single titre) = 40. Culture for Francisella tularensis and polymerase chain reaction (PCR) diagnosis was carried out for drinking water, firewood, and domestic animals at the mill. Fifteen cases of tularaemia (38%) were confirmed. Twelve of the cases (80%) had the pulmonary form. None of the patients was admitted to hospital. There was a strong association between infection and participation in a dinner at the mill on 4 August (p < 10(-8)). One of the three dogs present in the dining room was serologically positive for F. tularensis. Results of analysis of environmental samples were negative. These investigations confirmed the occurrence of a cluster of 15 tularaemia cases, in patients who were infected on the evening of 4 August, in a mill in VendAe, an endemic area for tularaemia. The investigations highlight the existence of nonspecific and benign pulmonary forms of the illness in France. The pulmonary form of infection in the human cases and the positive serology of the dog suggest contamination by inhalation of contaminated particles from the dogos fur disseminated by the dog shaking itself.

Surveillance of human listeriosis in France, 2001-2003

Mandatory notification of listeriosis began in France in 1999. Enhanced public health surveillance, including routine molecular characterisation of Listeria monocytogenes strains, epidemiologic follow up of cases, and collection of food samples, has improved the sensitivity of outbreak detection and response. The incidence of listeriosis declined from 4.5 cases/million in 1999-2000 to approximately 3.5 cases/million during the period 2001-2003. Clinical, demographic and microbiological characteristics of listeriosis in France remained stable during this time period. Maternal-fetal infections accounted for 24% of all cases. Serovar 4b accounted for 49% of cases and 60% of case clusters. The incidence of listeriosis in France has declined and is now lower than in several other European countries.

Association between indicators of cattle density and incidence of paediatric haemolytic-uraemic syndrome (HUS) in children under 15 years of age in France between 1996 and 2001: an ecological study

Over the past years Shiga-like toxin-producing Escherichia coli (STEC) O157:H7 emerged as an important cause of severe gastrointestinal illnesses and haemolytic-uraemic syndrome (HUS) with up to 10% of children infected with STEC developing HUS. We conducted a geographical ecological study using the district as the statistical unit. For each district, we estimated the incidence of HUS among children <15 years for the period 1996-2001 from national HUS surveillance data and data obtained on cattle density. We used multivariate Poisson regression to quantify the relation, adjusted for covariates, between paediatric HUS incidence and exposure to cattle. In univariate analysis, a positive association was observed between several cattle-density indicators and HUS incidence. In multivariate analysis, HUS paediatric incidence was associated with dairy cattle density and the ratio of calves to children <15 years (P<0.001). Our findings are consistent with previous studies in other countries and support the recommendation to limit exposure of children to dairy cattle and manure to reduce the risk of STEC infection.

Molecular epidemiology of caliciviruses detected in sporadic and outbreak cases of gastroenteritis in France from December 1998 to February 2004

We compiled sequence and epidemiological data from 172 caliciviruses detected in France from December 1998 to February 2004 in sporadic and outbreak cases. The results showed a cocirculation of strains with a majority of genogroup II (GII) noroviruses. Three groups of noroviruses, not detected before in our laboratory, emerged and spread during the period: the recombinant GGIIb and Norwalk-related strains not amplified in the polymerase gene in 2000 and a new Lordsdale variant in 2002. We observed that (i) GII-4 noroviruses were predominant in nursing home and hospital outbreaks but rare in oyster- and water-related outbreaks despite continuous circulation in the population; (ii) at the opposite, genogroup I strains were detected in the majority of environmental outbreaks; (iii) several strains were frequently found in oyster- and water-linked outbreaks (up to seven), whereas one single strain was detected when transmission was from person to person; and (iv) whereas GII noroviruses were predominant in sporadic cases where patients were under 15 years of age, GI strains were more frequent in outbreaks occurring in this age group. Finally, from a methodology point of view, this compilation shows that detection and characterization in the polymerase gene are not adequate in a significant number of cases and should be completed by amplification and sequencing in the capsid gene.

Surveillance of listeria infections in Europe

In addition to the economic consequences and threats associated with outbreaks, listeriosis remains of great public health concern, as it has one of the highest case fatality rates of all the foodborne infections (20%-30%), and has common source epidemic potential. Changes in the way food is produced, distributed and stored have created the potential for diffuse and widespread outbreaks involving many countries. In 2002, a survey was carried out to assess the need for and the feasibility of a European network on listeria infections in humans. Data on surveillance systems and laboratory methods were collected through two postal surveys sent to the national Centres for communicable disease surveillance and to the listeria reference laboratories. Surveillance systems for listeria infections were in operation in 16 out of the 17 countries surveyed, and 16 countries had a national reference laboratory (NRL). All countries based their case definition of listeriosis on the isolation of Listeria monocytogenes. Fourteen NRLs performed at least one typing method on human strains. At least 13 countries already carried out or expressed willingness to carry out characterisation of isolates by pulsed field gel electrophoresis (PFGE) of L. monocytogenes strains isolated from human cases following a standard protocol. The participants concluded that there was a clear added value to having a European surveillance network for listeria infections, particularly for outbreak detection and investigation, and that a surveillance network based on the existing national surveillance systems was feasible.