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FOOD SAFETY AND  
  FOODBORNE ILLNESS
  
EMERGING FOODBORNE 
  DISEASES

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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 
year. 
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 
China. 


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 
outbreaks. 

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 
soil. 


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 
this practice. 
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 
food additives. 
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 
Organization (WTO). 
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 
animals. 

--------------------------------------------------------------------------------

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: inf@who.int 






Fact Sheet Nฐ 124
(Revised) November 1996

EMERGING FOODBORNE DISEASES

BACKGROUND:

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 
cholera transmission.

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 
pathogen.

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/