Introduction
In the late 1970s, the development in Campylobacter isolation techniques resulted in enhanced detection of Campylobacter infections. Since then, thermotolerant Campylobacter species Campylobacter jejuni and Campylobacter coli have been included amongst the most important causative agents of acute diarrhoea in the industrialised world (1). The reported numbers of campylobacteriosis are increasing in many European countries, revealing that these infections are emerging and becoming a major public health problem in Europe (2). Campylobacter is among the diseases for which a European-wide surveillance has been decided (Commission Decision 2000/96/EC). However, at this time, no information on the tools and schema used to diagnose Campylobacter infections or surveillance systems for human campylobacteriosis on local and national levels in European countries was available. To assess the feasibility of a European network on human Campylobacter infections, two surveys were conducted. The first survey collected the information about the diagnostic methods and procedures in national reference centres as well as the existing surveillance systems among 18 European countries. The second survey obtained information about diagnostic methods and procedures in primary laboratories that investigate patient samples among 10 European Union (EU) countries. The project, supported by the European Commission (DG SANCO) (3), has been conducted by the Robert Koch-Institut (RKI) in Berlin. Partners from national public health institutes and European networks, Enternet and Campynet, cooperated on the project.

Methods
Survey 1
This survey concerned the National Reference Laboratories (NRLs) and Surveillance systems from the 15 Member States, Norway, Iceland and Switzerland. It focused on the following aspects:
- Existence of NRLs, tasks of NRLs, methods for Campylobacter isolation, identification and molecular sub-typing, quality assurance and accreditation (4).
- Surveillance systems (statutory/sentinel), case definitions, other data sources, reported numbers of cases, recorded outbreaks.
Survey 2
All countries willing to participate (10) were included in the second survey. These countries were Austria, Denmark, Finland, France, Germany, Greece, Republic of Ireland, Italy, Portugal and the United Kingdom (UK). The questionnaire was tested in five countries (France, Germany, the UK, The Netherlands, Republic of Ireland) by 14 laboratories before final revision. The following information was collected:
A. Basic information (type of laboratory, patient groups, total number of investigations, sample transport, routine methods for testing, submitted patient information)
B. Sample handling and culture practices (published method, time interval between sampling and cultivation, procedures before cultivation, cultivation practices, plate preparation and quality control, confirmation and typing methods, storing and sending isolates, reporting, antimicrobial susceptibility testing).
C. External quality assurance (participation, accreditation).
The questionnaire was translated into French (Institut de Veille Sanitaire), German (Robert Koch-Institut) and Italian (Istituto Superiore di Sanità). The data entry of the French questionnaires was performed in France and the data were added to the total database in Berlin. Epi Info 6.04 and SPSS 10.07 were used for data analyses.

Results and discussion
Campylobacter surveillance systems in Europe
Of 18 countries that responded to the first survey, 17 had developed a surveillance system for Campylobacter infections (figure). Nine countries had a statutory system and seven countries had a sentinel system which covered only part of the population. One country had both systems.
The reporting partners were physicians, laboratories, local health authorities and hospitals. In nine countries, the laboratories were the only notifying partners among both statutory and sentinel systems. In one country, the physicians were the only notifying partners in the statutory system. In the other countries, at least two partners reported the cases. At national level, national public health institutes (NPHI) collected the surveillance information in 14 countries, and NRLs in three countries. At European level, the main information flow was thus from the laboratories and physicians to the NPHIs. In 14 countries (82%), the information was forwarded as single cases.

Ten out of 17 countries had developed case definitions for Campylobacter surveillance. All included laboratory confirmation into the case definition but other criteria varied between the countries. At the European level, the facts to be considered for a case definition would be the inclusion/exclusion of an asymptomatic case and cases that are epidemiologically linked to a laboratory confirmed case (e.g. in outbreaks).
Demographic information about age and sex is most frequently (15/16 countries, no data available from Greece) transmitted to surveillance centres in statutory and sentinel systems. Travel history is routinely forwarded in nine countries. Five countries collect also the information about possible risk factors. Information about the suspected source of infection is submitted in six countries.

Trends of Campylobacter infections in Europe
Fifteen out of 18 countries reported 134 971 Campylobacter infections in 1999. Based on reported numbers, the notifications / 100 000 inhabitants ranged from 2.9 to 166.8 between countries in 1999. In 1998, the mean number of notifications / 100 000 inhabitants in the EU (n=15) was 61 (95% CI 47 - 78) and in 1999 it was 71 (95% CI 56 - 90). The increase in notifications was thus about 16% between 1998 and 1999.
During the five year period from 1995 to 1999, 11 countries reported 154 outbreaks. The highest number of reported outbreaks was in 1997. As the reporting of outbreaks varied greatly by country, however, the numbers are only a rough estimate of the true situation. In 48% of the reported outbreaks, food was the likely vehicle of transmission. For 15%, consumption of unpasteurised milk was reported as the source of infection and another 15% were waterborne. In every fifth outbreak (21%), the cause remained unknown or was not reported. An analytical epidemiological study (case-control or cohort study) was carried out in 14% of the reported outbreaks.

National reference laboratories for Campylobacter in Europe
In the survey among 18 European countries, 13 countries reported having a national reference laboratory (NRL) or a laboratory performing reference tasks (later referred as a NRL). The most commonly mentioned tasks of NRLs were: confirmation of results of primary laboratories (n=12), development of new typing (n=10) and analytical (n=9) methods, development of proposals for standardisation of methods (n=9) and conduction of training courses (n=7). In seven countries, the NRLs carried out also a routine primary investigation for Campylobacter from stool samples. Although 12 NRLs (92%) reported confirming the results of primary laboratories, only about 13% (range 6% - 100%) of primary laboratories in Europe reported sending the isolated strains routinely or occasionally to the NRLs for confirmation or further characterisation. This indicates that in most countries the strains are not collected centrally by the NRLs.
There exists no commonly applicable method to subtype Campylobacter strains. Serotyping with commercial antisera is possible, but not all strains are typeable with commercial antisera. NRLs in four countries serotyped the strains routinely according to the modified Penner scheme. Phage typing was used in the UK only. Antimicrobial resistance patterns were used as a typing method in eight NRLs. The genotyping methods varied between the countries and one NRL may use several molecular subtyping methods. Direct DNA based analyses of chromosomal or extrachromosomal genetic elements were performed in 9 countries. Of these, pulsed field gel electrophoresis (PFGE) was used in 8 countries. PCR based profiling was performed in 7 countries.

Campylobacter diagnosis and reporting from primary laboratories in Europe
A total of 1014 (41%, range 17-92%) primary laboratories from 10 EU countries responded to the survey. Of these, 622 (61%) performed primary Campylobacter diagnosis (table). Taking into account the infrastructures and information available in each country, the results were considered representative, even though the sampling methods and response rates varied between countries.
As the target group in some countries was not easy to determine, the survey, at first, also included laboratories that did not perform Campylobacter diagnostics. This was the case in Germany. In the UK for example, the laboratories are a sub sample of laboratories belonging in the national sentinel surveillance system. They had gone through an assessment before inclusion in the national sentinel surveillance system. Most of the Campylobacter laboratories were either hospital based (53%, range 27% -100%) or private laboratories (41%, range 0-72%). The private laboratories played a major role in France and Germany.
In European primary laboratories, the method for isolation and confirmation of Campylobacter from stool samples was principally the same. However, the mean number of positive tests/100 tested samples (mean isolation rate) varied from 2.2 - 6.2 between the countries indicating that there are significant differences in investigation routines and/or methods used to culture Campylobacter. In three countries, all stool samples were tested for Campylobacter. In these countries, the primary laboratories were more likely to have an isolation rate >4.00 (>4 positive results per 100 samples tested for Campylobacter) (OR 4.4, 95% CI 1.6 - 12.1) indicating that routinely performed Campylobacter investigation may yield to better isolation rate. In the other seven countries, the ratio between incoming stool samples and performed Campylobacter investigations was about 2:1 in 1999.
Principally, the laboratories reported positive findings via the local health authorities to the national level. At European level, only few primary Campylobacter laboratories reported their positive findings directly to the national surveillance centre (10%) or the NRL (4%). In only three countries did over 80% of primary laboratories report directly to the national surveillance centre.

Quality assurance in Campylobacter diagnostic
The NRLs in six countries (46%) reported having internal quality assurance procedures e.g. media control and monitoring the growth conditions. About half of primary Campylobacter laboratories (47%) reported controlling the quality of media. Laboratories that prepared the agar plates themselves also controlled the quality of plates (Spearman rs=0.88, p<0.01).
NRLs in four countries reported having EQA (external quality assurance) to control their diagnostic performances and six NRLs planned to adapt an EQA system. Of primary Campylobacter laboratories, 44% reported participating in EQA schemes for Campylobacter culturing in their country. However, many laboratories (40%) did not know if there were EQA schemes available in their country. This indicates that information about the EQA schemes available in Europe should be better disseminated among laboratories.
Antimicrobial susceptibility testing
About half of primary Campylobacter laboratories (46%) reported always performing antimicrobial susceptibility testing. Most frequently, the susceptibility for erythromycin (92%) and ciprofloxacin (83%) was tested. The NRLs in 12 countries reported performing antimicrobial susceptibility testing for Campylobacter. Usually, the susceptibility for nalidixic acid and cephalotin was used for species differentiation whereas the susceptibility for ciprofloxacin and erythromycin was used for clinical purposes. Among those laboratories that performed susceptibility testing for Campylobacter, agar diffusion method was routinely used in most NRLs (67%, n=12) and primary Campylobacter laboratories (85%, n=342).

Conclusion
The results of the surveys indicate that a basic infrastructure for a European wide Campylobacter surveillance exists. Almost all EU countries have developed a national surveillance system for Campylobacter. Most countries receive the notifications as single cases enabling an efficient data analysis. Many countries receive travel information on a routine basis within their surveillance systems making it possible to assess travelling as a risk factor for a country.
Although it appears that the reported number of outbreaks has declined since 1997, it may not reflect the actual situation, because very few countries systematically collect data from outbreaks. The low percentage of performed epidemiological studies indicates a strong need for epidemiological training and leaves doubts on the evidence of reported vehicle. However, the total number of reported cases is increasing yearly in many European countries. There is a need to make joint efforts to stop the increase and determine the risk factors with joint epidemiological investigations.
The diagnostic procedure is principally the same throughout Europe at local, national and international levels, but there is evidence of significant differences in methodological procedures that should be studied further. Contact between national and local laboratories appears to be relatively rare. In some countries, however, the cooperation between national and local level functions well.
There is a strong need for a standardised molecular sub-typing method which would be applicable in many countries. These methods could be used to detect international outbreaks and links between apparently sporadic cases. As the Campynet group has been working to achieve this goal, this group's results should be taken into account in network planning.
Antimicrobial susceptibility testing methods were basically the same in most countries both at local and national levels. This provides a good basis for the surveillance of antimicrobial resistance patterns.

Recommendations
As the trends of human Campylobacter infections show increasing numbers, and a good basic infrastructure for Campylobacter surveillance exists in almost all EU countries, it is strongly recommended to implement an EU-wide surveillance network1. At first, the network should aim to standardise the collection of data and then develop the network step by step. Since in most of the countries data are available at the National Surveillance Centres, they should be the national contact points in the network. Countries with no surveillance or with mixed surveillance systems should be supported to organise and build up their systems in a way that produces comparable data. The collection of data from outbreaks and antimicrobial resistance should be incorporated into the surveillance from the beginning. To achieve this, the epidemiological and methodological training both on national and international level should be strengthened in Europe. At some point, a European-wide epidemiological study could be performed. As Campylobacter infections are zoonoses, good cooperation between physicians, veterinarians and epidemiologists is essential for a successful surveillance network. The network should have cooperational ties to expert groups such as Campynet and the Community Reference Laboratory for the Epidemiology of Zoonoses. Countries should be encouraged to collect travel history information routinely, in order to obtain information on travelling as a risk factor at Community level.
In many countries, the interaction between primary laboratories and NRLs should be improved. NRLs should actively offer primary Campylobacter laboratories the information about diagnosis and quality assurance procedures. The laboratories, both at local and national levels, should be encouraged to consider carefully the need to control the different steps in their diagnostic procedures and the need for adopting an EQA system.

1 Note: no European Network for Campylobacter surveillance has been implemented so far. Enternet has made a proposal to add Campylobacter surveillance into current activities which has been accepted in principle by the European Commission. Until such time as there is a microbiological typing method of choice in place surveillance under Enternet will remain at a low level of activity. However, the European Centre for Disease Control and Prevention should be established in the near future and it could help in coordinating to build up European wide surveillance networks.

Campylobacter Working Group:
G. Feierl, Institut of Hygiene, AUSTRIA;
F. Van Loock, Scientific Institute of Public Health, BELGIUM;
P. Gerner-Smidt, Statens Seruminstitut, DENMARK;
S. On, Danish Veterinary Laboratory, DENMARK;
P. Ruutu, National Public Health Institute, FINLAND;
A. Gallay, Institut de Veille Sanitaire, F. Megraud, Centre de National des Campylobacters et Helicobacter, FRANCE;
A. Käshbohrer, Community Reference Laboratory for Zoonoses, Federal Institute for Health Protection of Consumers and Veterinary Medicine, GERMANY
M. Kist, Konsiliarlaboratorium für Campylobacter, Freiburg, GERMANY;
J. Bockenmühl, Hygieneinstitut, Hamburg, GERMANY;
S. Chatzipanagiotou, National and Kapodistrian University of Athens, GREECE;
H. Briem, Section for Infectious Disease Control, Directorate of Health, ICELAND;
D. O´Flanagan and D. Igoe, National Disease Surveillance Centre, IRELAND;
I. Luzzi, Istituto Superiore di Sanitá, ITALY;
F. Schneider, Laboratoire National de Santé, LUXEMBOURG;
Y. Van Duynhoven, National Institute of Public Health and Environment, NETHERLANDS;
J. Wagenaar, Institute for Animal Science and Health, NETHERLANDS;
P. Aavitsland, National Institute of Public Health, NORWAY;
J. Cabrita, Instituto Nacional de Saúde, PORTUGAL;
G. Pezzi, Instituto de Salud Carlos III, SPAIN;
Y. Andersson, Institute for Infectious Disease Control, SWEDEN;
H. Schmid, Federal Office of Public Health, SWITZERLAND;
D. Newell, Veterinary Laboratories Agency, UK;
I. Fisher, Enter-net Surveillance Hub, PHLS Communicable Disease Surveillance Centre, UK;
S. O´Brien, PHLS Communicable Disease Surveillance Centre, UK.