The free movement of people and foodstuffs between countries are effective ways of distributing disease internationally. There is a requirement for a mechanism whereby data and information on potential outbreaks of foodborne pathogens can be disseminated rapidly to those who need to know. The Enter-net dedicated surveillance network provides this mechanism, complemented by the Salm-gene molecular typing network. Data on epidemiological and microbiological features on current cases, as well as background levels of infections are immediately available within the Enter-net databases. The Salm-gene network with its database of harmonized salmonella PFGE patterns from the participating European countries provides immediate, and electronically exchangeable, DNA fingerprints of outbreak strains. This prompt electronic dissemination of information regarding unusual events with international implications ensures that public health interventions can be implemented and cases of foodborne disease prevented.

In 2002, in The Netherlands a national study of gastroenteritis outbreaks was performed. Epidemiological information was collected by the Public Health Services (PHS) and the Food Inspection Services (FIS) using standardized questionnaires. Stool samples were collected for diagnostic testing. For foodborne outbreaks, food samples were taken. In total, 281 gastroenteritis outbreaks were included, mainly from nursing homes and homes for the elderly (57%), restaurants (11%), hospitals (9%) and day-care centres (7%). Direct person-to-person spread was the predominant transmission route in all settings (overall 78%), except for restaurant outbreaks where food was suspected in almost 90% (overall in 21% of outbreaks). The most common pathogen was norovirus (54%), followed by Salmonella spp. (4%), rotavirus group A (2%), Campylobacter spp. (1%) and only incidentally others. In conclusion, most outbreaks were reported from health and residential institutions, with norovirus as the dominant agent. Control should aim at reducing person-to-person spread. In foodborne outbreaks norovirus was common, due to contamination of food by food handlers. Salmonella, as the second foodborne pathogen, was mainly associated with raw shell eggs. These results stress the continuous need for food safety education, complementary to governmental regulation.

Sporadic outbreaks of cyclosporiasis, a common cause of protracted diarrhoea in underdeveloped countries, are often undetected and undiagnosed in industrial countries. In May 2001, an outbreak of Cyclospora cayetanensis gastroenteritis was identified in British Columbia, Canada, with 17 reported cases. We conducted a case-control study involving 12 out of the 17 reported and confirmed case patients. Eleven (92%) of the patients had consumed Thai basil, an essential ingredient in Vietnamese cuisine, compared to 3 out of 16 (19%) of the control patients (P=0·003). Trace-back investigations implicated Thai basil imported via the United States as the vehicle for this outbreak. This is the first documented sporadic outbreak of cyclosporiasis linked to Thai basil in Canada, and the first outbreak of cyclosporiasis identified in an ethnic immigrant population. This outbreak provides the opportunity to increase our understanding of this emerging pathogen and improve on our prevention and control for future outbreaks.

In August 2003, an outbreak of scombroid fish poisoning occurred at a retreat centre in California, USA. In a retrospective cohort study, 42 (75%) of the 56 dinner attendees who ate escolar fish (Lepidocybium flavobrunneum) met the case definition. Individuals who ate at least 2 oz of fish were 1·5 times more likely to develop symptoms than those who ate less (relative risk 1·5, 95% confidence interval 0·9–2·6), and to develop more symptoms (median 7 vs. 3 symptoms, P=0·03). Patients who took medicine had a longer duration of symptoms than those who did not (median 4 vs. 1·5 h, P=0·05), and experienced a greater number of symptoms (median 8 vs. 3 symptoms, P=0·0002). Samples of fish contained markedly elevated histamine levels (from 2000 to 3800 ppm). This is one of the largest reported outbreaks of scombroid fish poisoning in the United States and was associated with a rare vehicle for scombroid fish poisoning, escolar.

An increase in gastroenteritis outbreaks due to Norovirus has been reported worldwide. We investigated a large-scale outbreak affecting 246 residents and 33 staff members in six nursing homes in the Tel-Aviv district, Israel, during 3 weeks in 2002. Person-to-person spread was noticed in all nursing homes. The spread of disease could not be attributed to social interactions. Among the elderly residents, the hospitalization rate was 10·2% and the case-fatality rate was 2·0%. Bacteriological cultures were negative. Overall, 7 out of 15 stool specimens were positive for Norovirus by RT–PCR. All were sequenced and found to be 90% identical. The characteristics of this outbreak and the RT–PCR results suggest that illness was caused by Norovirus. Due to the high case-fatality rate of Norovirus gastroenteritis, there should be a high index of suspicion when encountering a gastroenteritis outbreak among the elderly. This will enable prompt action to stop the spread of illness.

An outbreak of acute gastroenteritis of suspected viral aetiology occurred in April 2003 in the British Royal Fleet Auxillary ship (RFA) Argus deployed in the Northern Arabian Gulf. There were 37 cases amongst a crew of 400 personnel. Of 13 samples examined from cases amongst the crew, six enteric viruses were detected by reverse transcriptase polymerase chain reaction (RT–PCR). Five different viruses were identified including, three norovirus genotypes, a sapovirus and a rotavirus. No multiple infections were detected. A common food source was implicated in the outbreak and epidemiological analysis showed a statistically significant association with salad as the source of the outbreak, with a relative risk of 3·41 (95% confidence interval of 1·7–6·81) of eating salad on a particular date prior to the onset of symptoms. Faecal contamination of the salad at source was the most probable explanation for the diversity of viruses detected and characterized.

Seasonal peaks in both human campylobacter infections and poultry isolates have been observed in several European countries but remain unexplained. We compared weekly data on human campylobacter infections with thermophilic Campylobacter isolation rates from fresh, retail chicken samples (n=514) purchased weekly in Wales between January and December 2002. Human isolates (n=2631) peaked between weeks 22 and 25 (early June) and chicken isolates (n=364) between weeks 24 and 26 (late June). In the absence of a temporal association, we postulate that the seasonal rise in humans is not caused by a rise in isolation rates in poultry but that both are more likely to be associated with a common, but as yet unidentified, environmental source.

The molecular epidemiology of 98 isolates of Salmonella serovar Agona (n=27), S. Montevideo (n=42) and S. Senftenberg (n=29) from wild-living gulls, fish-meal factories, feed factories, humans and domestic animals was investigated using pulsed-field gel electrophoresis (PFGE) and computerized numerical analysis. Two of the S. Agona profiles were identified both in gulls and in two of the factories. In addition, one of these profiles was detected in two infected poultry farms. Two of the S. Montevideo profiles were also identified both in gulls and in two of the factories, and one of these profiles was observed in a human isolate. Four factories shared an identical S. Senftenberg profile. The S. Senftenberg profile found in gulls was not identified in any other source investigated. The presence of isolates with identical PFGE profiles indicates potential epidemiological links between different factories, as well as between gulls and factories.

A total of 455 highly tetracycline-resistant Escherichia coli strains were isolated from 84 healthy swine from abattoirs and it was found that 56·9, 43·1, 22·2, 15·4, 2·6 and 1·5% of strains were resistant to chloramphenicol, ampicillin, kanamycin, trimethoprim–sulphamethoxazole, ofloxacin and gentamicin respectively. Interestingly, E. coli strains isolated from certain finisher hog groups exhibited resistance against 2–7 antimicrobials, but strains isolated from multiparous sow groups in each herd were resistant to only 2–4 antimicrobial agents. When randomly selected 108 tetracycline-resistant isolates were tested for the presence of resistance genes, the following genes tet(A) (n=6), tet(B) (n=95), tet(D) (n=1) or both tet(A) and tet(B) (n=6) were found to be distributed among them. Furthermore, 52 isolates carried the integrase 1 gene and 24 strains gave five different PCR amplicon profiles using primers from the variable region of integron. Extensive nucleotide sequence analyses of these amplicons revealed the presence of dhfrI, dhfrXII, dfr17, aadA, aadA2, aadA5, aadA21, aacA4 and catB3 genes which code for different antibacterial resistance proteins.

Estimation of the degree of undercount is important for disease surveillance. Capture–recapture techniques are now being used to evaluate the completeness of disease ascertainment. This study estimated the level of under-notification of giardiasis in the Auckland adult population using a capture–recapture method. Two independent datasets of giardiasis cases [ges ]15 years were generated from the 1998–1999 Auckland Giardiasis Study (AGS) case database and cases notified to Auckland Regional Public Health Services (ARPHS) for the same period of time. Cases were matched and under-notification was estimated using a two-sample capture–recapture method. During the 12-month period, 199 cases participated in the AGS and 413 cases were notified to ARPHS. The capture–recapture calculation indicated that only 49% of cases were notified. Under-notification by a factor of 2 obscures the true burden of giardiasis. Socio-economic conditions and water quality may influence disease notification inversely. Capture–recapture techniques are useful in evaluating the completeness of surveillance.

A total of 162 clinical isolates of Shigella collected from children in a semi-rural community of Chile were examined for the presence of genetic determinants of resistance to ampicillin, chloramphenicol, tetracycline, and trimethoprim. Ampicillin resistance was most frequently associated with the presence of blaOXA in S. flexneri and with blaTEM in S. sonnei. The blaOXA gene but not blaTEM was located in class 1 integrons. The dhfrIa gene encoding for resistance to trimethoprim was associated to class 2 integrons and detected exclusively in S. flexneri, whereas dhfrIIIc was found in all S. sonnei strains and in 10% of the S. flexneri isolates. Cat, coding for choramphenicol resistance, and blaOXA genes were located in the chromosome in all cases, whereas tetA gene, coding for tetracycline resistance, and blaTEM, dhfrIa and dhfrIIIc genes were found either in the chromosome or in conjugative plasmids. Our results show a heterogenous distribution of antibiotic-resistance determinants between S. flexneri and S. sonnei.

A mathematical model was used to evaluate the impact of the Italian Measles National Elimination Plan (NEP), and possible sources of failure in achieving its targets. The model considered two different estimates of force of infection, and the possible effect on measles transmission of the current Italian demographic situation, characterized by a below-replacement fertility. Results suggest that reaching all NEP targets will allow measles elimination to be achieved. In addition, the model suggests that achieving elimination by reaching a 95% first-dose coverage appears unlikely; and that conducting catch-up activities, reaching high vaccination coverage, could interrupt virus circulation, but could not prevent the infection re-emerging before 2020. Also, the introduction of the second dose of measles vaccine seems necessary for achieving and maintaining elimination. Furthermore, current Italian demography appears to be favourable for reaching elimination.

We reviewed measles surveillance data for 1993–2002 to determine the impact of Australia's measles control initiatives. The introduction of a second dose of measles–mumps–rubella (MMR) vaccine for 10- to 16-year-olds in 1993 was followed by marked reductions in measles notifications and hospitalizations, especially in the targeted age group. Further rate reductions were achieved following the Measles Control Campaign (MCC) in 1998, which involved a catch-up campaign for primary-school-aged children and lowering the age for the second dose of MMR vaccine to 4 years. Since the MCC, outbreaks have continued to occur, but most had a source case who was infected overseas, which suggests that indigenous transmission has been interrupted. In addition, a greater proportion of cases have been in adults although infants aged <5 years still had the highest rates. In conclusion, Australia is making good progress towards measles elimination. However, as in other countries, this progress can be sustained only by maintaining high vaccination coverage with the routine childhood vaccination schedule.

An outbreak of influenza A occurred in a prison system in New South Wales, Australia in January 2003 during the southern hemisphere summer. This report documents only the third confirmed outbreak of influenza in a prison environment. The outbreak investigation included case ascertainment, state-wide surveillance, a case-control study and interventions to limit the outbreak such as infection control, quarantine, cohorting of cases, and the use of antiviral medication for prophylaxis. A total of 37 clinical cases were identified. Influenza A virus was detected in 11 of the 22 respiratory tract specimens collected. The virus was typed as an influenza A/Fujian/411/2002 (H3N2)-like virus. This strain subsequently became the predominant virus strain during the northern hemisphere winter and the following 2003 Australian southern hemisphere winter influenza season.

In The Netherlands, in May 1999 an enhanced surveillance of hepatitis B was begun to collect detailed information of patients with acute hepatitis B virus (HBV) infection. The objective was to gain insight in transmission routes and source of infection of new HBV cases. Through public health services, patients were interviewed on risk factors. It appeared that the majority (59%) acquired the infection through sexual contact; 52% of these by homosexual and 48% by heterosexual contact. In 60% of the heterosexual cases, the source of infection was a partner originating from a hepatitis B-endemic region. Sexual transmission is the most common route of transmission of acute hepatitis B in The Netherlands and introduction of infections from abroad plays a key role in the current epidemiology of HBV. As well as prevention programmes targeted at sexual high-risk groups, prevention efforts should focus more on the heterosexual transmission from HBV carriers.

The New York State hospital discharge database and the multiple cause-of-death file were used to estimate the mortality rate of hepatitis C in New York State excluding New York City in 1997. The mortality rate with hepatitis C was severely underestimated when each data source was used alone. Applying the capture–recapture method using the hospital discharge database and the multiple cause-of-death file appears to be an efficient method to estimate the mortality rate with hepatitis C.

The prevalence of hepatitis C and related risk factors in drug users were compared in two geographic regions in Belgium, the city of Antwerp and the mixed urban–rural area of Limburg. All 310 participants were surveyed and screened for hepatitis B, hepatitis C and HIV. Prevalence rates of anti-HCV, anti-HBc and anti-HIV were 71, 62 and 4% in Antwerp and 46, 21 and 0% in Limburg respectively. Injecting drug use, duration of injecting drug use, work as a commercial sex-worker, originating from Turkey or Northern Africa, marginalization and anti-HBc positivity were identified as independent predictors for hepatitis C infection. In this study an important difference in HCV seroprevalence among drug users in a methadone maintenance programme across two geographic regions in Belgium was demonstrated. This was explained not only by variations in drug-related risk behaviour, but also by differences in sexual risk behaviour and socio-economic status.

Herpesviruses can remain dormant in once-infected hosts and, upon reactivation, cause such hosts to become infectious. This phenomenon of latency and reactivation may enable herpesviruses to persist for a long time in small host populations. To quantify the effect of reactivation on persistence, the time to extinction of bovine herpesvirus type 1 (BHV-1) in small cattle populations was calculated. For realistic parameter values the mean time to extinction is already more than 100 years in a population of 10 animals. In a population of 20 animals the time to extinction is approximately 2000 years. The effects of vaccination on persistence were also studied, revealing that continued vaccination of the whole population could result in much faster eradication. For instance, in an isolated herd of 20 animals BHV-1 could be eradicated in 44 years.

Pertussis diagnosis among adults is primarily based on serology. In this study, receiver operation characteristics (ROC) analysis was utilized to evaluate three IgA, IgM and IgG ELISAs based on B. pertussis whole-cell sonicate (WC), pertussis toxin (PT), or combined PT-filamentous haemagglutinin (FHA) antigens in a healthy adult population and in adults suffering from symptoms consistent with pertussis. The assays were compared to a PT and FHA reference ELISA. The reference assay showed high correlation with PT- and PT-FHA-based ELISAs but low correlation was found with the WC-based ELISA. However, ROC analysis indicated that all the assays enabled fine differentiation between healthy subjects and subjects suffering from symptoms suggestive of pertussis. The WC IgA ELISA showed the best diagnostic performance [highest specificity (98·8%) with highest sensitivity (53·8%)]. We conclude that despite a low correlation between the various assays they all carry good diagnostic capability for an adult population.

High titres of pertussis toxin (PT) antibody have been shown to be predictive of recent infection with Bordetella pertussis. The seroprevalence of standardized anti-PT antibody was determined in six Western European countries between 1994 and 1998 and related to historical surveillance and vaccine programme data. Standardized anti-PT titres were calculated for a series of whole-cell and acellular pertussis vaccine trials. For the serological surveys, high-titre sera (>125 units/ml) were distributed throughout all age groups in both high- (>90%) and low-coverage (<90%) countries. High-titre sera were more likely in infants in countries using high-titre-producing vaccines in their primary programme (Italy, 11·5%; Western Germany, 13·3%; France, 4·3%; Eastern Germany, 4·0%) compared to other countries (The Netherlands, 0·5%; Finland, 0%). Recent infection was significantly more likely in adolescents (10–19 years old) and adults in high-coverage countries (Finland, The Netherlands, France, East Germany), whereas infection was more likely in children (3–9 years old) than adolescents in low-coverage (<90%; Italy, West Germany, United Kingdom) countries. The impact and role of programmatic changes introduced after these surveys aimed at protecting infants from severe disease by accelerating the primary schedule or vaccinating older children and adolescents with booster doses can be evaluated with this approach.