Introduction
Since it began in 1993 (as Salm-Net), the Enter-net dedicated surveillance
network has been collating data on salmonella infections in humans in
its international database. These data have previously shown that although
salmonellosis in the participating countries declined in the early 1990s
then rose in mid-1990s [1,2], it still remains a major public health concern.
This report shows the trends in the main salmonella serotypes in the six
years from 1998 to 2003.
Methods
An agreed subset of national data is electronically tranferred to the
Enter-net surveillance hub on a regular (usually monthly) basis. These
data are collated in the Enter-net international databases, and include
microbiological (such as the salmonella serotypes identified) and epidemiological
data for all 'sporadic' and 'outbreak' cases identified by the national
reference laboratories. The data are incorporated into the Enter-net
salmonella database, analysed and the results returned to the participants
within the network. Public domain versions of these reports are posted
on the Enter-net section on the Health Protection Agency's web site
(http://www.hpa.org.uk/hpa/inter/enter-net_menu.htm).
Results
Twenty-four countries have supplied comparable data covering the period
1998-2003, with a total of just over 1 million records [FIGURE]. Salmonella
enterica serotypes Enteritidis and Typhimurium are the predominant organisms
identified by the countries' national reference laboratories, making
up over 80% of all isolates.
For all salmonellas the general trend is declining with 77 807 fewer
laboratory confirmed cases in 2003 compared with 1998 (a reduction of
35.3%). Salmonella Typhimurium and other serotypes showed a slight increase
in 2001 over 2000 (but not Enteritidis) but the downward trend for all
three returned in 2002. Over the six-year period, Enteritidis fell by
36.2% from 154 928 cases to 98 915, Typhimurium by 26.6% from 25 790
to 18 937 and the other serotypes by 35.3% from 39 980 to 25 039.
Discussion
The incidence of salmonellosis from cases of human infections in participating
countries is on the decline, although with almost 143 000 laboratory-confirmed
cases in 2003, salmonellosis remains a major cause of morbidity. This
is a significant underestimate of the true incidence due to underreporting,
sampling of isolates in each country and other factors. Much has still
to be done to further reduce salmonella infections. The added value
of international surveillance networks such as Enter-net is vital in
helping to identify supranational trends in infections as well as international
outbreaks. Inclusion of data from all Enter-net participants will elucidate
the problem in a wider range of countries. Some data from the new EU
member states has been included in this report, but the extension of
Enter-net should provide the opportunity for more countries to supply
their data. In addition, information from non-human sources would be
a valuable adjunct to those included in the Enter-net human salmonella
database.
While the data within the Enter-net database are comparable over time,
because surveillance systems have stayed relatively stable, it is not
as yet possible to compare the disease burden between countries. To
achieve this, population-based studies similar to those done in England,
France and the Netherlands [3,4,5] are required to determine the multiplier
needed to convert laboratory confirmed cases to the number of cases
occurring in the community. This should be a priority for Enter-net
participating countries, to ensure truly comparable data, and to inform
policy makers, public health bodies and the general public of the true
burden of infection.
Acknowledgements
The Enter-net Dedicated Surveillance Network is funded by the European
Commission - DG SANCO under the Public Health Programme 2003-2008, grant
agreement number 2003203.
This paper could not have been prepared without the contribution of
all of the Enter-net participants;
Management team: N Gill, H Smith, W Reilly
Austria: F Allerberger, C Berghold, R Strauss;
Australia*: G Hogg;
Belgium: J-M Collard, S Quoilin, D Pierard;
Bulgaria*: G Asseva, S Raycheva;
Canada*: L-K Ng, P Sockett;
Cyprus: D Bagatzouni, C Hadjianastassiou;
Czech Republic: D Dedicová, R Karpiskova, M Prikazska;
Denmark: P Gerner-Smidt, K Mølbak, F Scheutz;
England, Wales and Northern Ireland: SJ O'Brien, GK Adak, EJ
Threlfall, LR Ward;
Estonia: U Joks, J Varjas;
Finland: M Kuusi, A Siitonen;
France: H de Valk, P Grimont;
Germany: A Ammon, H Karch, H Tschäpe;
Greece: K Mellou, PT Tassios, A Vatopoulos;
Hungary: M Herpay, K Krisztalovics;
Iceland: H Hardardottir, G Sigmundsdottir;
Ireland: M Cormican, P McKeown, E McNamara;
Italy: A Caprioli, I Luzzi, A Tozzi;
Japan*: N Okabe, H Watanabe;
Latvia: I Jansone, I Selga;
Lithuania*: G Zagrebneviene;
Luxembourg: P Huberty-Krau, F Schneider;
Malta: P Cushcieri, M Micallef;
the Netherlands: Y van Duynhoven, W van Pelt, W Wannet;
New Zealand*: F Thomson-Carter, D Phillips,
Norway: J Lassen, L Vold;
Poland: A Cieslik, J Szych;
Portugal: C Furtado, J Machado;
Romania: M Damian;
Scotland: J Coia, J Cowden, M Hanson;
Slovakia: Z Kristufkova;
Slovenia: T Cretnik, A Grom;
South Africa*: K Keddy;
Spain: A Echeita, G Hernández-Pezzi;
Sweden: Y Andersson, S Löfdahl, R Wollin;
Switzerland*: H Hächler, H Schmid, and all others in each
of the participating institutes who provide input into the successful
running of the Network, and of course Francine Stalham as the Enter-net
administrator.
* not funded under the grant agreement.
In particular, those countries which have provided the data that have
been used in preparing this report should be thanked; Australia, Austria,
Belgium, the Czech Republic, Denmark, England, Wales and Northern Ireland,
Finland, France, Germany, Greece, Hungary, Ireland, Italy, Lithuania,
Luxembourg, the Netherlands, Norway, Poland, Portugal, Romania, Scotland,
Spain, Sweden, and Switzerland.
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