Food Safety 327these compounds were introduced for use in
animals.
In recent years a new range of foods has been
implicated with food-borne disease. For instance, the
internal contents of an egg were always presumed to
be safe to eat raw, and uncooked eggs have been tra-
ditionally used in many different food products. This
situation has changed with the emergence of S. Enter-
itidis infection in egg-laying fl ocks, resulting in
contamination in shell eggs and a major increase
in food-borne illness worldwide associated with
uncooked eggs. Animal products are no longer the
only focus for food safety controls, as fresh produce
is emerging as an important vehicle for food-borne
disease (McCabe-Sellers and Beattie, 2004). Between
1990 and 2003, 12% of food-borne outbreaks in the
USA were linked to produce and produce dishes; the
most common produce foods being salads and alfalfa
sprouts. Of the produce-associated outbreaks, 40%
were due to norovirus or hepatitis A, and 30% were
caused by bacteria commonly associated with an
animal reservoir, such as Campylobacter, E. coli O157
and Salmonella (Dewaal et al., 2006).
Finally, chemical risks to food, such as pesticide
residues, acrylamide, and the use of food additives,
continue to concern consumers.
14.3 Food-borne bacteria
The major cause of food-borne diseases is the con-
sumption of microbiologically contaminated foods.
There are many types of food-borne pathogens,
including bacteria, viruses, and parasites. The charac-
teristics of food-borne bacterial intoxications and
infections are summarized in Tables 14.1 and 14.2,
respectively. Food-borne pathogens are covered in
more detail by Doyle et al. (2001).
14.4 Food-borne viruses
It is only in recent years that the role of viruses as
etiological agents of food-borne illness have emerged.
Diffi culties in attributing viral illness to food have
mainly been due to the diagnostic diffi culties in
detecting viruses in an implicated food and under-
reporting owing to the mild nature of illness in many
cases. A report from the US Centers for Disease
Control (CDC) in 2000, on surveillance of food-
borne disease outbreaks from 1993 to 1997, revealed
that viruses accounted for 6% of all food-borne out-
breaks and 8% of cases. Hepatitis A accounted for the
majority of these, followed by norovirus. Data pub-
lished by the European Food Safety Authority (EFSA)
revealed that viruses accounted for 10.2% of all food-
borne outbreaks reported during 2006. Caliciviruses
(including norovirus) accounted for the majority
(61.7%) of these food-borne viral outbreaks.
Food-borne viruses are generally enteric, being
transmitted by the fecal–oral route. However, trans-
mission by person-to-person contact and via con-
taminated water is common. Hepatitis A and norovirus
are more commonly transmitted via foods than other
food-borne viruses. The most important food-borne
viruses are hepatitis A, norovirus, astrovirus, and
rotavirus. These are discussed in detail below.Hepatitis A virus
Hepatitis A is one of the more severe food-borne
diseases. The illness results from immune destruction
of infected liver cells, and a few weeks of debility
are common (Table 14.3). It is a member of the
picornaviruses.
Infections are more likely to be asymptomatic or
mild in young children than in adolescents or adults.
The virus can be shed in feces for up to 14 days before
the onset of illness. It is therefore possible for an
infected food handler with poor personal hygiene
(hand-washing, in particular) to contaminate food
during this period. The virus may be shed in the feces
for 1–2 weeks after onset of symptoms.
Food becomes contaminated with this virus via
infected persons or via fecally contaminated water, as
is usual with shellfi sh. Examples of other foods impli-
cated in hepatitis A outbreaks are oysters, raw mussels,
drinking water, bakery products and caviar. Hepatitis
A has been shown to be more heat resistant than most
enteric viruses and is also quite resistant to drying.
The virus is susceptible to chlorination treatment,
however, and water-borne hepatitis A outbreaks have
been linked to untreated water.Noroviruses
Norovirus was the fi rst enteric virus reported to be
food-borne. It was formerly known as Norwalk-like
virus (NLV) or small round structured virus (SRSV)
and has recently been classifi ed as a member of the
calicivirus family. Noroviruses are diffi cult to detect,
especially from foods.