Forum on Home Hygiene
Background Information on Foodborne
Disease and the home
What is food poisoning?
Any disease of an infectious or toxic nature caused by or thought to be
caused by the consumption of contaminated food or water.
What are the main pathogens that cause
The main microbial causes of food poisoning are bacteria (e.g. Salmonella,
Campylobacter, Escherichia coli O157, Clostridium, Staphylococcus aureus
and Bacillus cereus) and viruses (e.g. Norovirus).
Campylobacter, Salmonella, Clostridium perfringens, verocytotoxin producing
Escherichia coli (VTEC), Norovirus and Listeria monocytogenes are estimated
to account for 85% of foodborne disease in England and Wales.
How does food and water become
- Foodborne pathogens frequently originate from the gastrointestinal
tract of the animals from whom the meat is produced. In some cases the
animal is perfectly healthy e.g. cows who carry E. coli 0157 are
themselves “healthy”. There are many opportunities for meat or poultry to
become contaminated as it is slaughtered and prepared for sale.
- Animals can also transmit food borne pathogens to humans via their
produce e.g. milk, eggs
- Therefore, raw foods of animal origin as purchased for consumption in
the home are the most likely foods to be contaminated, i.e. raw meat and
poultry, raw eggs, unpasteurized milk, and raw shellfish.
- Outbreaks can also occur where vegetables or other farm produce
becomes contaminated e.g. from contaminated water or raw sewage.
During food processing (either during production or in the home),
intestinal pathogens can also be introduced from infected people who handle
the food, or by cross contamination from some other raw foods. The latter
occurs either by direct or indirect cross-contamination from contaminated
raw food such as meat, poultry and eggs to other foods e.g. cooked meats or
salads to be eaten without further cooking:
- Up to 25% of chickens sold through retail outlets in the UK are
contaminated with Salmonella and up to 83% contaminated with
Campylobacter. Similar or even higher figures are reported from other
- A UK study showed that 6% of the outside of retail poultry packaging
was contaminated with Campylobacter and/or Salmonella.
- 0.4%-0.8% of meat products purchased from UK butchers were positive
for E. coli O157.
Examples of Number of Reported Food
- England and Wales: >72,000 cases in 2002
- Scotland: 7682 cases in 2002
Although the number of cases recorded is in the thousands, the true
burden of food poisoning is likely to be millions of cases per year, as most
cases go unreported.
England & Wales: According to the UK Food Standards Agency (FSA), up to half
of the annual 9.4 million cases of infectious intestinal disease (IID) are
food poisoning. This equates to up to 4.7 million cases per year.
UK: In a 2003 FSA survey, [MSOffice1] 16% of respondents said they had
suffered food poisoning in last 12 months. This equates to up to 7.6 million
cases per year.
US: Foodborne illness is estimated to cause 76 million illnesses, 500,000
hospital admissions, and 9000 deaths each year.
New Zealand: Foodborne illness estimated to cause 119,000 cases, 19000 GP
visits, 400 hospital admissions, 22 cases of long term illness and 2 deaths
What proportion of foodborne infection
occurs in the home?
In 2003, the World Health Organisation reported that as much as 40% of all
foodborne infections are a result of food eaten within the home.
How does food poisoning occur in the home?
Of foodborne IID outbreaks in the home, UK data suggests that:
- 39% are due to inappropriate storage of food
- 31% are due to inadequate cooking
- 20% are due to cross-contamination
The purpose of cooking food is to reduce the numbers of bacteria or
viruses to a level insufficient to cause disease. Both home-cooked foods
and purchased cold foods such as cold ham, etc. should contain only small
numbers of human pathogens that are insufficient to cause disease. However,
if left in warm or ambient and moist conditions overnight organisms can
multiply and the food can become highly contaminated by the next day.
- After heating, food must spend the minimum amount of time between
- If not eaten immediately, food must be cooled immediately to prevent
the potential growth of bacteria.
- Freezing prevents bacteria from growing and refrigeration will delay
- Neither freezing nor refrigeration will inactivate bacteria, which
means that on transferring these foods to room temperature they may become
heavily contaminated again if left at warm temperatures.
Cross-contamination or contamination from an infected food handler,
indicative of poor hygiene standards is thought to be responsible for about
20% of outbreaks in the home. This can involve either direct or indirect
cross-contamination. An example of direct cross-contamination is where an
infected person directly contacts the food. Indirect cross contamination is
where the transfer of micro-organisms is via another vector such as a knife
or a dishcloth.
In the kitchen, micro-organisms can be transferred from one food to another
food by using the same chopping board or knife to prepare both without
washing the surface or knife in between. A food that is fully cooked can
become re-contaminated if it touches other contaminated raw foods or drips
and spills from raw foods.
Cloths and sponges become contaminated when they are used to wipe up spills
from food, and bacteria can multiply with time once on damp cloths and
sponges. Afterwards the cloths and sponges serve as a vector for further
spread of pathogens to the hands of the user, to the surfaces wiped and then
to many articles throughout the kitchen.
- A recent study has shown that during the preparation of a meal in a
domestic kitchen using a contaminated chicken almost 1 in 5 (17%) of hands
and hand and food contact surfaces become contaminated with Salmonella or
- In a US study of 23 patients infected with E. coli 0157, 80% of the
cases were thought to have originated from consumption of hamburgers in
the home and food preparers in those home were significantly less likely
to report washing their hands or work surfaces. The transmission was
believed to have occurred more often when the hands of food preparers were
allowed to cross-contaminate other food and utensils.
- An outbreak of Norovirus at a wedding reception affecting 50% of
guests was due to cross-contamination of potatoes from a contaminated
sink, into which the food handler has previously vomited.
PAGE \# "'Page: '#'
'" Page: 1