Investigation of an outbreak of Salmonella enterica serovar Newport infection.

A 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.

Mumps outbreak among young people in Northern Ireland.

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.

Haemophilus influenzae type b (Hib) vaccination and uptake predictors in Northern Ireland.

In order to study selected factors affecting the uptake of Haemophilus influenzae type b (Hib) vaccine a case control study was undertaken in residents of the Southern Health and Social Services Board in Northern Ireland. Standard data from the child health computer system were used. Residents in the catchment area of the health board born between 1 January and 30 June 1993 were defined as cases (unvaccinated) and controls (vaccinated). The uptake of Hib vaccination and odds ratios for factors associated with non-completion of vaccination were calculated. Overall uptake of Hib vaccination exceeded 97%. Children of mothers who smoked or children who had two or more younger siblings were less likely to have been vaccinated.

Vaccine efficacy in a measles immunisation programme.

During a measles outbreak in Northern Ireland (between October 1988 and March 1989) it was noted that a proportion of cases had occurred in children who had previously been vaccinated against measles. A study was, therefore, set up to provide a rapid estimate of vaccine efficacy. Vaccine efficacy was calculated to be 94% (95% confidence limits, 91% to 96%). Investigation of the computerised records at 31 December 1991 revealed that 94% of children in the study cohort had received measles vaccine. As vaccination coverage increases, a higher proportion of cases of measles will, inevitably, have a history of vaccination.

Measles in the Southern Health Board--implications for resources.

During a recent epidemic of measles in the Southern Health and Social Services Board in Northern Ireland it became apparent that the level of notifications of measles by general practitioners did not reflect the true incidence of the disease at that time. In trying to establish a more accurate measure of the incidence of measles it became clear that much money and manpower had been used to treat this outbreak. We tried to cost a defined period covering 1 January to 30 June 1983 to draw attention to the possible benefits of a more effective measles vaccination programme in preventing disease and saving resources. The implications of our present poor rate of vaccination were measured for hospital services, primary medical care services, and related consequences. The costs for the defined period were approximately pounds 175 931, and if the outcome had been worse in a few cases it might have been as high as pounds 1 375 931.

Possible method of identifying spotter practices in a health board in Northern Ireland.

We examined the notification of infectious diseases, including measles, by general practitioners over 18 months, which included a measles epidemic in the area covered by the Southern Health and Social Services Board in Northern Ireland. Of the 156 general practitioners who provided services in the area, 27 (17.3%) had a pattern of notification which might render them acceptable as "spotter" practices, a system which at present does not exist in Northern Ireland, although it is used in the rest of the United Kingdom. In future we hope to be able to; (i) predict impending epidemics of infectious disease; (ii) mobilise Health Service resources to minimise the effects of such epidemics; (iii) monitor the effects of improving the level of uptake of measles vaccine.