FOOD SAFETY AND
การเกษตร ผัก ผลไม้
WHO, Geneva, Switzerland. |
Fact Sheet Nฐ237
Revised September 2000
Food safety is an increasingly important public health issue. Governments all over the
world are intensifying their efforts to improve food safety. These efforts are in
response to an increasing number of food safety problems and rising consumer
| Definition of Foodborne Illness: Foodborne illnesses are defined as
diseases, usually either infectious or toxic in nature, caused by
that enter the body through the ingestion of food. Every person is at
risk of foodborne illness.
Magnitude of Foodborne Illness: Foodborne diseases are a widespread and growing
public health problem, both in developed and developing countries.
The global incidence of foodborne disease is difficult to estimate, but it has been
reported that in 1998 alone 2.2 million people, including 1.8 million children, died from
diarrhoeal diseases. A great proportion of these cases can be attributed to
contamination of food and drinking water. Additionally, diarrhoea is a major cause of
malnutrition in infants and young children.
In industrialized countries, the percentage of people suffering from foodborne
diseases each year has been reported to be up to 30%. In the United States of America (USA), for example, around 76 million cases of foodborne diseases,
resulting in 325 000 hospitalizations and 5 000 deaths, are estimated to occur each
While less well documented, developing countries bear the brunt of the problem due
to the presence of a wide range of foodborne diseases, including those caused by
parasites. The high prevalence of diarrhoeal diseases in many developing countries
suggests major underlying food safety problems.
While most foodborne diseases are sporadic and often not reported, foodborne
disease outbreaks may take on massive proportions. For example, in 1994, an
outbreak of salmonellosis due to contaminated ice cream occurred in the USA,
affecting an estimated 224 000 persons. In 1988, an outbreak of hepatitis A, resulting
from the consumption of contaminated clams, affected some 300 000 individuals in
Major Foodborne Diseases from Microorganisms
Salmonellosis is a major problem in industrialized countries. Salmonellosis is caused
by the Salmonella bacteria and symptoms are fever, headache, nausea, vomiting,
abdominal pain and diarrhoea. Examples of foods involved in outbreaks of
salmonellosis are eggs, poultry and other meats, raw milk and chocolate.
Campylobacteriosis is a widespread infection. It is caused by certain species of
Campylobacter bacteria and in some countries, the reported number of cases
surpasses the incidence of salmonellosis. Foodborne cases are mainly caused by
foods such as raw milk, raw or undercooked poultry and drinking water. Acute health
effects of campylobacteriosis include severe abdominal pain, fever, nausea and
diarrhoea. In two to ten percent of cases the infection may lead to chronic health
problems, including reactive arthritis and neurological disorders.
Infections due to enterohaemorrhagic
(causing intestinal bleeding) E. coli, e.g. E.coli O157, and listeriosis are important foodborne diseases which have emerged over the
last decades. Although their incidence is relatively low, their severe and sometimes
fatal health consequences, particularly among infants, children and the elderly, make
them among the most serious foodborne infections.
Pathogenic Escherichia coli strains, such as E. coli O157, which produce a potent
(vero-) toxin cause haemorrhagic infections in the colon, resulting in bloody diarrhoea
or life-threatening complications such as kidney failure. E. coli O157 outbreaks have
been mainly related to beef, but sprouts, lettuce and juice have also caused
Listeria monocytogenes is the cause of listeriosis which has a fatality rate of up to
30%. The most frequent effects are meningitis and miscarriage or meningitis of the
foetus or newborn. Many types of foods have been implicated in listeriosis cases.
Often a long refrigeration period seems to have contributed to outbreaks.
Cholera is a major public health problem in developing countries, causing enormous
economic losses. The disease is caused by Vibrio cholerae, a bacterium. In addition
to water, contaminated foods can be the vehicle of infection. Different foods, including
rice, vegetables, millet gruel and various types of seafood have been implicated in
outbreaks of cholera. Symptoms, including abdominal pain, vomiting and profuse
watery diarrhoea, may lead to severe dehydration and possibly death, unless fluid
and salt are replaced.
Other Food Safety Problems
Some major examples are:
Naturally occurring toxins, such as mycotoxins, marine biotoxins, cyanogenic
glycosides and toxins occurring in poisonous mushrooms, periodically cause severe
intoxications. Mycotoxins, such as aflatoxin and ochratoxin A, are found at measurable
levels in many staple foods; the health implications of long-term exposure of such
toxins are poorly understood.
Unconventional agents such as prions, associated with cattle suffering from bovine
spongiform encephalopathy (BSE, or "mad cow disease"), are suspected to cause
new variant Creutzfeldt-Jakob Disease in humans. Consumption of meat and meat
products is a potential route for transmission of prions to humans.
Persistant Organic Pollutants (POPs): Dioxins and PCBs (polychlorinated biphenyls)
exist in the environment and in the human body. Dioxins are unwanted by-products of
industrial processes, especially waste incineration. Exposure to POPs may result in a
wide variety of adverse effects in humans.
Metals, such as lead and mercury, cause neurological damage in infants and
children. Exposure to cadmium can also cause kidney damage, usually seen in the
elderly. These (and POPs) may contaminate food through pollution of air, water and
Costs of Foodborne Diseases
Food contamination creates an enormous social and economic burden on
communities and their health systems. In the USA, diseases caused by the major
pathogens alone are estimated to cost up to US $37.1 billion annually in medical
costs and lost productivity. The re-emergence of cholera in Peru in 1991 resulted in
the loss of US $700 million in fish and fishery product exports.
Challenges and Developments in Food Safety
The safety of food derived from biotechnology needs to be carefully assessed. To
provide the scientific basis for decisions regarding human health, new methods and
policies to assess such food need to be developed and agreed upon internationally.
The assessment should consider health benefits as well as possible negative health
implications. Crops modified to resist pests, foods with allergens removed or food with
an increase of essential nutrients are possible examples of the former, while
anti-microbial markers in some genetically modified foods have been suggested to
be an example of the latter.
The weighing of potential risks and benefits is an important aspect of assessment of
foods derived from biotechnology that has not received much attention in the past.
Likewise, clear communication of the basis for safety assessment in this area is
generally lacking at national and international levels.
If not properly monitored and assessed, changes in animal husbandry practices,
including feeding, may have serious implications for food safety. For example,
changes in the production process of ruminant bone and meat meal used as a feed
supplement for cattle might have played a role in the emergence of BSE.
Adding low levels of antibiotics to animal feed in order to increase growth rate has
raised concern about the transfer of antibiotic resistance to human pathogens from
Modern intensive agricultural practices contribute to increasing the availability of
affordable foodstuffs and the use of food additives can improve the quality, quantity
and safety of the food supply. However, appropriate controls are necessary to ensure
their proper and safe use. Pre-market review and approval followed by continuous
monitoring are necessary to ensure the safe use of pesticides, veterinary drugs and
Other challenges, which need to be addressed to help ensure food safety, include the
globalization of trade in food, urbanization, changes in lifestyles, international travel,
environmental pollution and natural and manmade disasters. The food production
chain has become more complex, providing greater opportunities for contamination
and growth of pathogens. Many outbreaks of foodborne diseases that were once
contained within a small community may now take on global dimensions.
Future Directions for Food Safety at the World Health Organization (WHO)
In partnership with other stakeholders, WHO is developing policies that will further
promote the safety of food. These policies will cover the entire food chain from
production to consumption and will make use of different types of expertise.
Future work of the WHO Food Safety Programme will include strengthening food
safety systems, promoting good manufacturing practices and educating retailers and
consumers about appropriate food handling. Education of consumers and training of
food handlers in safe food handling is one of the most critical interventions in the
prevention of foodborne illnesses.
WHO is promoting in-country laboratory-based surveillance of priority foodborne
diseases, as well as the monitoring of pathogens in food. In co-operation with its
Member States, WHO is working to support the development of internationally
agreed-upon guidelines for data collection in countries. WHO is also compiling
outbreak and surveillance databases, and is broadening its epidemic surveillance
capacity to include foodborne disease outbreaks.
WHO is expanding its global network of participating institutions to monitor chemical
contamination of the food supply, particularly in developing countries.
WHO is promoting the use of all food technologies which may contribute to public
health, such as pasteurization, food irradiation and fermentation.
WHO is undertaking an important new initiative to strengthen the scientific basis of
food safety activities through the establishment of a WHO/FAO (Food and Agriculture
Organization of the United Nations) expert advisory body to assess microbiological
risks in food.
WHO is increasing its involvement in the work of the FAO/WHO Codex Alimentarius
Commission, whose standards, guidelines and recommendations are regarded as
the international reference for food safety requirements by the World Trade
Biotechnology has become a major public issue in developed as well as developing
countries. WHO will support Member States in providing the scientific basis for
health-related decision regarding food derived from biotechnology. WHO, jointly with
FAO, will convene a series of expert consultations to assess the safety and nutritional
aspects of foods derived from genetically modified plants, microorganisms, and
For further information, journalists can contact :
WHO Press Spokesperson and Coordinator, Spokesperson's Office,
WHO HQ, Geneva, Switzerland / Tel +41 22 791 4458/2599 / Fax +41 22 791 4858 / e-Mail: firstname.lastname@example.org
Fact Sheet Nฐ 124
(Revised) November 1996
EMERGING FOODBORNE DISEASES
Some foodborne diseases are well recognized, but are considered emerging
because they have recently become more common. For example, outbeaks of
salmonellosis have been reported for decades, but within the past 20 years the
disease has increased in incidence on many continents. In the Western hemisphere
and in Europe, Salmonella serotype Enteritidis (SE) has become the predominant
strain. Investigations of SE outbreaks indicate that its emergence is largely related to
consumption of poultry or eggs.
However, in 1994, there was a nationwide outbreak of salmonellosis in the United
States as a result of contamination of pasteurized ice cream during transport in lorries
that had previously carried nonpasteurized liquid eggs containing Salmonella
enteritidis. It is estimated that 224,000 persons were affected by the outbreak.
While cholera has devastated much of Asia and Africa for years, its introduction for the
first time in almost a century into the Western hemisphere in 1991 makes it another
example of an infectious disease that is both well-recognized and emerging. While
cholera is often waterborne, many foods also transmit infection. In Latin America, ice
and raw or underprocessed seafood are important epidemiological pathways for
Other foodborne pathogens are considered emerging because they are new
microorganisms or because the role of food in their transmission has been
recognized only recently. Infection with Escherichia coli serotype O157:H7 (E. coli)
was first described in 1982. Subsequently, it has emerged rapidly as a major cause of
bloody diarrhoea and acute renal failure. The infection is sometimes fatal, particularly
in children. Outbreaks of infection, generally associated with beef, have been
reported in Australia, Canada, Japan, United States, in various European countries,
and in southern Africa.
In 1996, an outbreak of Escherichia coli O157:H7 in Japan affected over 6,300 school
children and resulted in 2 deaths. This is the largest outbreak ever recorded for this
Listeria monocytogenes (Lm) is considered emerging because the role of food in its
transmission has only recently been recognized. In pregnant women, infections with
Lm can cause abortion and stillbirth, and in infants and persons with a weakened
immune system it may lead to septicemia (blood poisoning) and meningitis. The
disease is most often associated with consumption of foods such as soft cheese and
processed meat products that are kept refrigerated for a long time because Lm can
grow at low temperatures. Outbreaks of listeriosis have been reported from many
countries, including Australia, Switzerland and the United States. Two consecutive
outbreaks of Listeria monocytogenes in France in 1992 and 1993 were caused by
contaminated pork tongue and potted pork.
Foodborne trematodes are also emerging as a serious public health problem,
especially in south-east Asia, in part due to a combination of increased aquaculture
production, often under unsanitary conditions, and of underprocessing of aquaculture
products during their preparation. Foodborne trematodes can cause acute liver
disease, and may lead to liver cancer.
WHY DO FOODBORNE DISEASES EMERGE?
New foodborne disease threats occur for a number of reasons. These include
international travel and trade, microbial adaptation and changes in the food
production system, as well as human demographics and behaviour.
# The globalization of the food supply. A large outbreak of Shigella sonnei infections
occurred in Great Britain, Norway, and Sweden in 1994 due to contaminated lettuce
imported from southern Europe.
# The inadvertant introduction of pathogens into new geographic areas. Vibrio
cholerae was introduced into waters off the coast of southern United States when a
cargo ship discharged contaminated ballast water in 1991. It is likely that a similar
mechanism led to the introduction of cholera for the first time this century into Latin
America in 1991.
# Travellers, refugees, and immigrants exposed to unfamiliar foodborne hazards
while abroad. International travellers may become infected by foodborne pathogens
that are uncommon in their countries. It is estimated that about 90% of all cases of
salmonellosis in Sweden are imported.
# Changes in microorganisms. Changes in microbial populations can lead to the
evolution of new pathogens, development of new virulent strains in old pathogens,
development of antibiotic resistance that might make a disease more difficult to treat,
or to changes in the ability to survive in adverse environmental conditions.
# Change in the human population. The population of highly susceptible persons is
expanding world-wide because of ageing, malnutrition, HIV infections and other
underlying medical conditions. Age is an important factor in susceptibility to
foodborne infections because those at the extremes of age have either not
developed or have partially lost protection from infection. Particularly for the elderly,
foodborne infections are likely to invade their blood stream and lead to severe illness
with high mortality rates. People with a weakened immune system also become
infected with foodborne pathogens at lower doses which may not produce an adverse
reaction in healthier persons. Seriously ill persons, suffering, for example, from cancer
or AIDS, are more likely to succumb to infections with Salmonella, Campylobacter,
Listeria, Toxoplasma, Cryptosporidium, and other foodborne pathogens. In
developing countries reduced immunity due to poor nutritional status render people,
particularly infants and children, more susceptible to foodborne infections.
# Changes in lifestyle. Greater numbers of people go out and eat meals prepared in
restaurants, canteens, fast food outlets, and by street food vendors. In many countries,
the boom in food service establishments is not matched by effective food safety
education and control. Unhygienic preparation of food provides ample opportunities
for contamination, growth, or survival of foodborne pathogens.
All food-borne diseases pose a considerable threat to human health and the
economy of individuals, families and nations. Their control requires a concerted effort
on the part of the three principal partners, namely governments, the food industry and
consumers. As part of its food safety education campaign, WHO issued the 10
Golden Rules for Safe Food Preparation and a guide on Safe Food for Travellers.
For further information please contact Mr Valery Abramov, Health Communication and Public Relations, WHO, Geneva, Switzerland. Tel. (41 22) 791 2543 or Fax (41 22) 791 4858.
All WHO Press Releases, Fact Sheets and Features can be obtained on Internet on the WHO home page http: //www.who.ch/