Survival analysis Cox regression models using an outbreak of gastroenteritis as the endpoint were fitted to identify institutional and operational attributes related to increased outbreak rates at the level of the care unit.
Foodborne disease outbreak rates were highest in northern states, and most waterborne disease outbreaks occurred in states bordering the Mississippi River.
Before the outbreak, rates of GIH events in the elderly were similar in south, central, and north areas (Table 2).
From 1995 to 2000, 1,643 outbreaks of viral gastroenteritis were investigated by the Public Health Laboratory Service in England and Wales, but the outbreak rates (number of outbreaks/population) were highest in Sweden for every surveyed year.
Therefore, the results of this study should be put in context, and the derived estimates of particular outbreak attributes (e.g. outbreak rates, population attack rates, outbreak durations, and disease morbidity comparisons) may not be comparable to other epidemiological studies which use more traditional outbreak investigation designs.
During the outbreak, rates of GIH events in elderly persons increased in all three water supply areas, but the increase was much stronger in the southern and central areas than in the northern area.
After the outbreak, rates of laboratory-confirmed cryptosporidiosis from 1993 to 1995 were 31.2 44.2 per 100,000 in Allerdale and Copeland compared to 19.8 to 23.9 per 100,000 in the neighboring local government districts of Carlisle and Eden.
We compared the median outbreak size and state outbreak rates (outbreaks with exposure occurring in a single state/sum of state populations during 2003 2012, from U.S. Census Bureau intercensal estimates) using the Kruskal-Wallis test, and performed categorical analyses using χ and Fisher exact tests; 2-tailed p values <0.05 were considered significant.
Outbreak rates were higher for the larger ships with 6.6 outbreaks per 100 ship-weeks, compared to the smaller ships with 2.6 outbreaks per 100 ship-weeks, but this difference was not statistically significant (Incidence-rate ratio 2.5, 95% exact CI 0.5 9.9).
While these eruptions generally have a steady eruption rate, larger outbreaks of lava have been observed at many flow-dominated eruption sites.
