SUMMARYA large outbreak of Salmonella enterica serotype Newport infection occurred in Northern Ireland during September and October 2004. Typing of isolates from patients confirmed that this strain was indistinguishable from that in concurrent outbreaks in regions of England, in Scotland and in the Isle of Man. A total of 130 cases were distributed unequally across local government district areas in Northern Ireland. The epidemic curve suggested a continued exposure over about 4 weeks. A matched case-control study of 23 cases and 39 controls found a statistically significant association with a history of having eaten lettuce in a meal outside the home and being a case (odds ratio 23·7, 95% confidence interval 1·4–404·3). This exposure was reported by 57% of cases. Although over 300 food samples were tested, none yielded any Salmonella spp. Complexity and limited traceability in salad vegetable distribution hindered further investigation of the ultimate source of the outbreak.

An outbreak of mumps occurred in the Mid-Ulster area of Northern Ireland between 1st November 1999 and 31st August 2000, with 729 cases notified. Salivary test results were obtained for 430 (59%) reported cases, of which 332 (77%) were positive for mumps IgM antibody. Three hundred and sixteen (95.2%) of these confirmed cases were in the age range 9 to 19. One hundred and eighty-four (55.4%) confirmed cases had received one dose of MMR (measles, mumps and rubella) vaccine, but only 3 (0.9%) confirmed cases had received 2 doses of MMR. The low incidence of mumps among children who had received two doses of MMR illustrates the importance of the second dose of MMR for full protection.

The number of whooping cough notifications has declined in recent years, as vaccine coverage has recovered from the low levels seen in the 1970s and 1980s. Notification of infectious disease is often incomplete, and this study aimed to estimate the extent to which whooping cough is undernotified. We included all cases of whooping cough occurring in the North West Region between 1 April 1994 and 31 December 1996, identified by notification, hospital admission data, or laboratory reports. By combining the three sources, 1239 cases were identified, 69.6% of which were notified. The notification rate was 29.6% (131/442) for cases admitted to hospital and 45.6% (78/170) for laboratory reported cases. Completeness of notification was estimated to be 35.7% (863/2420; 95% confidence interval 30.3-43.4%) using the capture-recapture method. The study confirms that notification of whooping cough is incomplete and suggests that two thirds of cases are not notified.