The human ecology of climate change - Climate Change: Biological and Human Aspects - page 402

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Month

Fig. 7.12 Reportedcasesof Salmonellaenteritidis bymonthinEnglandandWalesin1995-7.AfterStanwell-Smith

(1999).

so a disease's range will also change, as will the disease organism's population if not
controlled.
As with humans and the annual temperature cycle outside of the tropics, so micro-
bial populations vary. The incidence of reported cases of food poisoning in developed
nations is illustrative of such annual cycles, with cases peaking in the summer months.
In the UK the number of officially notified food-poisoning cases was rising in the
late 20th century, so that by 1998 it had reached about 100 000 per year. However,
notifications do not always strongly correlate with monthly temperature and some-
times are more strongly associated with the previous month's temperature. This is
not due to incubation period, as this is usually short (typically less than 2 days), and
it is not the result of delays in notification, because the UK system is designed for
prompt reporting. It is possibly to do with the level of infections in animals prior
to slaughter, as meat is an important source of food poisoning. Consequently global
warming does not just present a challenge to consumers but also to those responsible
for food production, processing and transportation (Bentham, 1999).
The annual pattern of reported cases of Salmonella enteritidis by month in England
and Wales is typical (see Figure 7.12). Campylobacter species show a similar pattern
with a summer maximum. Campylobacter enteritis has been linked to barbecues,
particularly those involving chicken. Nonetheless, this only explains a small propor-
tion of UK outbreaks and a very few of the sporadic cases. However, that cases of
Campylobacter- related illness are rising has made this species of interest to those
engaged in climate change and microbial-disease research in the UK.
This pattern of summer increase in temperate-zone incidence of food poisoning
suggests that in a warmer world there will be more such cases. Worldwide, the WHO
and the UN Food and Agriculture Organization (FAO) estimate that there are at least
two billion people affected by food poisoning each year, and many die. For example,
in Asia alone some 700 000 people die due to food- and water-borne (contaminating
food) disease (WHO/FAO, 2004).