distinguished from strains responsible for the statistical background
‘noise’ of sporadic cases. Such schemes have also enabled international
outbreaks of salmonellosis to be identified through the Enter-net sur-
veillance network which was started by the European Union but now
includes countries such as Australia, Canada, New Zealand, Japan and
Mexico. Even so, it is probable that many outbreaks remain undetected,
submerged in the numbers for sporadic cases.
Annual reports of statistics on food poisoning and isolations ofSalmo-
nellahave been published for England and Wales since 1949 and showed
no discernible trend until the 1980s when a steady increase was apparent
(Figure 6.4). A similar but smaller increase was noted in Scotland. Nearly
Figure 6.3 The food poisoning pyramid
(P. Sockett, PhD thesis)
168 Food Microbiology and Public Health