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  • Food and waterborne diseases

Food and waterborne diseases

The incidence of food and waterborne diseases has risen sharply in recent years, partly due to increased international travel and import of food. Many diseases are probably not registered, such as from contaminated water and infection with norovirus (“stomach flu”).

Illustration: Norwegian Institute of Public Health

The incidence of food and waterborne diseases has risen sharply in recent years, partly due to increased international travel and import of food. Many diseases are probably not registered, such as from contaminated water and infection with norovirus (“stomach flu”).

Main points

  • Every year, 5000-7000 cases of food and waterborne diseases are registered (often referred to as "food poisoning"). The recorded cases are just the tip of the iceberg.
  • Imported food is the source of infection in many outbreaks.
  • Norovirus is probably the most common cause of domestic food and waterborne disease cases.
  • Many disease cases are infected when travelling abroad.
  • Since 2009, travel-related Salmonella infections have declined due to reduced prevalence in poultry in European countries.
  • The water supply network in Norway has special challenges due to dispersed populations, many small waterworks and a poor quality pipe infrastructure.
  • Norway still has one of Europe's lowest incidences of infection from food and animals.

About food and waterborne infections

A variety of bacteria, viruses and parasites transmitted through food and water can cause disease. The severity and duration of disease vary considerably (NIPH, 2016a; Kapperud, 2015).

Surveillance at the Norwegian Institute of Public Health shows that the most common cause of food and waterborne infection in Norway is norovirus, with Campylobacter, Salmonella and E. coli next in line (NIPH, 2016a, 2016b, 2016c):

  • Norovirus
  • Campylobacter
  • Salmonella
  • Shigella
  • E. coli
  • Listeria
  • Yersinia

Food and waterborne infections in Norway today

Several infectious food and waterborne diseases are notifiable to the Norwegian Surveillance System for Communicable Diseases (MSIS) (NIPH, 2016b). In addition, outbreaks are monitored by the NIPH’s rapid alert  system, Vesuv. An outbreak is defined as more cases of disease than expected with a suspected common source of infection. Outbreaks related to food and water should be reported immediately (NIPH, 2016d).

Every year, several thousand food and waterborne disease cases and 40-70 outbreaks are registered, although this is just the tip of the iceberg (Kapperud, 2015). Many people who become ill do not seek medical attention and doctors do not always take samples from patients, so many cases go unregistered.

Therefore, we have no exact figures for how many people become ill from food and water, although we can follow trends from notifications to MSIS and Vesuv. These show that a large percentage of the recorded cases were infected while travelling abroad. 

Norovirus infection

Food can be a source of infection for several different viruses, all of which are transmitted directly or indirectly from human faeces (NIPH, 2016a, 2016d). Some viruses can also be transmitted through vomiting.

Norovirus is the most common cause of gastrointestinal infection caused by a virus (“stomach flu”). It is believed to be responsible for a large proportion of the waterborne infectious diseases in Norway and other industrialised countries (NIPH, 2016d). See Table 1 below.


Campylobacter is the most common bacterial cause of diarrhoeal illness registered in Norway. About half of the registered cases are infected while travelling abroad (NIPH, 2016b, 2016e). In Norway, the bacterium is commonly found in the intestines of a wide variety of mammals and birds, both wild and domesticated. The animals may infect humans through direct contact or indirectly via food or water.

The largest known outbreaks of campylobacteriosis have been caused by contaminated drinking water, infecting sometimes more than a thousand people (NIPH, 2016c, 2016f). This was either due to livestock or wild birds polluting the water source, or inadequate disinfection.

See Table 1 and Figure 1 below.


Salmonella is the second most common cause of diarrhoeal disease registered. Most Norwegians who get salmonellosis are infected abroad (NIPH, 2016a, 2016b, 2016e). Most outbreaks are due to imported foods (NIPH, 2016c, 2016f).

Salmonella is rarely found in food produced in Norway and among Norwegian livestock. Some strains of the bacterium have become established among wild Norwegian fauna, particularly among small birds and hedgehogs. Every year, these Salmonella strains cause outbreaks of disease in humans.

See Table 1 and Figure 1 below.

Diseases caused by E. coli

Several strains of Escherichia coli (E. coli) are transmitted via food and water (NIPH, 2016a, 2016e). Some can cause serious illness, sometimes death, especially in children, the elderly and people with impaired immune defence.

Reported cases are modest, see Table 1 below, but the disease is significantly underdiagnosed.

E. coli can cause major, severe outbreaks. The best-known outbreak in Norway occurred in 2006 when at least 17 children became ill after eating cured sausage made from infected mutton. Ten of the cases developed severe renal failure (haemolytic-uremic syndrome, HUS), and one child died (Schimmer, 2008).


Bacteria belonging to the Shigella genus are the third most common cause of the registered cases of bacterial diarrhoeal illness in Norway (NIPH, 2016e). Over the last decade, the Norwegian Institute of Public Health has been notified of 80-160 cases of shigellosis annually, the majority (60-90 per cent) were infected when travelling abroad, see Table 1 below.

Humans are the disease reservoir and infection occurs directly from person to person, or indirectly via contaminated food or water.

Several outbreaks in Norway were caused by imported vegetables or herbs that were not heat-treated (NIPH, 2016c, 2016f).


In Norway, yersiniosis is caused by the bacterium Yersinia enterocolitica. Between 20 and 60 per cent of the reported cases are infected while travelling abroad, see Table 1. The bacterium is common in pigs and epidemiological studies show that pork, pork products and untreated drinking water are the main sources of infection for yersiniosis in Norway. However, after slaughter routines were improved in the mid-1990s, the incidence was significantly reduced to approximately 50-80 registered cases per year.

Several outbreaks have occurred, including several where pork brawn was the source of infection and one caused by imported salad. The biggest outbreak took place in 2014; the source of infection was probably a salad product (NIPH, 2016c). Many cases were registered in that year (133 cases).

The medical and socioeconomic consequences of yersiniosis are far greater than the number of cases would imply. The reason is that Y. enterocolitica can cause severe and sometimes chronic complications, more often than most other intestinal bacteria (NIPH, 2016a).


Listeriosis is a very serious disease with significant mortality, mainly affecting pregnant women and people with impaired immune defence (NIPH, 2016a).

The number of cases annually reported to MSIS is less than 100. Most cases are infected in Norway. See Table 1 below.

Hepatitis A

Hepatitis A is a viral infection that can cause liver inflammation (jaundice).

Most cases in Norway involve people who have visited countries where the disease is common. This has been the situation since the 1950s. There have only been a few isolated cases where individuals have infected others upon their return to Norway.

In recent years, we have seen a new situation with outbreaks of hepatitis A linked to imported frozen berries. With increased import of vegetables, fresh herbs, fruit and berries from countries where hepatitis A is common, we can expect more outbreaks and isolated cases of this disease in the coming years.

Table 1 provides an overview of the reported cases of food and waterborne infections, the proportion who are infected when travelling abroad and common sources of infection in Norway (NIPH, 2016b, 2016c, 2016e, 2016f).

Table 1. Food and waterborne infections: notified cases and sources of infection. In total, 5000-7000 cases are notified per year. Data source: MSIS 2008-2015.

Infectious disease agent

Notified cases per year

% infected abroad

Usual sources of infection in Norway *


Not notifiable**


  • Objects, food and drinking water contaminated by faeces or vomit from infected individuals



50-55 %

  • Drinking water
  • Chicken products
  • Barbecued food
  • Contact with animals



70-80 %

  • Small birds
  • Hedgehogs
  • Drinking water
  • Imported foodstuff

E. coli: EHEC


20-30 %

  • Meat and meat products from sheep or cattle
  • Other foodstuff contaminated by infected animals or people, including unwashed vegetables 
  • Drinking water



20-60 %

  • Pork products
  • Drinking water



> 90 %

  • Imported foodstuff
  • Objects, food and drinking water contaminated by faeces from infected individuals




  • Fermented fish, cured fish, smoked fish
  • Cooked coldcuts
  • Soft cheeses, e.g. blue mould cheeses, unpasteurised milk products

Hepatitis A virus


40-70 %

  • Imported foodstuff, particularly vegetables, fresh herbs, lettuce, fruit and berries
  • Objects, food and drinking water contaminated by faeces from infected individuals

EHEC = enterohaemorrhagic Escherichia coli, an E. coli type which causes bloody diarrhoea.

* In addition to the sources of infection specified in the table, contact with infected animals or people will be a source for all food and waterborne infections.

** Norovirus outbreaks are reported to the rapid alert system Vesuv at NIPH

*** 2014 deviates from the average; 211 cases were reported that year following a widespread outbreak where 133 became ill.

Trends: A growing international problem

Over the past 40 years, food and waterborne infectious diseases have become a growing health problem even in industrialised countries. This is mainly due to changes in animal husbandry, food production and trade patterns that accelerated after the Second World War (NIPH, 2016d).

The increase in Norway is mainly due to more people being infected while travelling in countries with higher disease burden and increased international trade in food products (NIPH, 2016c, 2016f).

Increase in campylobacteriosis: In the 1990s, a sharp increase in campylobacteriosis was registered in the western world, including Norway. In Norway, a peak occurred in 2013, see Figure 1. The cause is unknown, and there is a need for further research.

Decline in salmonellosis and yersiniosis
: Despite the increase seen for salmonellosis among Norwegians since the 1980s, since 2009 there have been fewer reported cases of this disease compared with previous years, see Figure 1. This is mainly due to a substantial reduction in the number of cases infected when travelling abroad. The decline is linked to reduced prevalence of Salmonella in poultry flocks and eggs in many European countries.

The number of cases of yersiniosis were significantly reduced after 1994-1995, when improved slaughtering techniques for pigs were introduced, see above. It is possible that reduced consumption of pork and a general improvement in drinking water quality has contributed to the decline in this disease.


Figure 1. Number of patients with campylobacteriosis and salmonellosis reported to MSIS annually. Source: MSIS 1980-2015. 

Increase in E. coli infections and listeriosis: Infections with enterohaemorrhagic E. coli (EHEC) and other E. coli strains show an increasing trend (NIPH, 2016b, 2016e). This increase can partly be explained by improved diagnostic methods, increased sampling and analysis, as well as greater awareness of the disease associated with outbreaks, although it may also be a real increase in incidence.

Over the longer term, listeriosis is showing an increasing trend, similar to trends in other European countries. The reason for the increase is unknown but may be due to an increase in the number of susceptible persons in the population, especially the elderly and people with impaired immune defence. The number of cases among pregnant women do not seem to be increasing (NIPH, 2016b, 2016e).

Norway has low rates compared to other countries

Infectious diseases transmitted by food and water are among the most common causes of illness and death worldwide.

Infection from food and animals

Norway still has one of Europe's lowest incidences of infection transmitted from food and animals. This is because the incidence of most infectious agents is relatively modest among Norwegian livestock and foods produced in Norway.

Norway is in a particularly favourable situation with Salmonella since these bacteria are rarely found in Norwegian-produced food and livestock.

Waterborne infection

In Norway, the burden of disease transmitted from water is assumed to be higher than in comparable countries. Part of the population consumes undisinfected surface water at cabins, holiday homes and in nature, and the water supply network is of poor quality. 11 per cent of the population obtain water from a private well or from small waterworks that are not obliged to send notifications (NIPH, 2016g).

Consequences of food and waterborne diseases

Food and waterborne diseases usually present as diarrhoea and only occasionally require hospitalisation or antibiotic treatment. These infections are rarely fatal in industrialised countries, unlike less developed countries. However, severe illnesses and deaths do occur, especially among vulnerable groups such as young children, frail elderly people, pregnant women, foetuses and people with impaired immune defence  (NIPH, 2016d; Kapperud, 2015).

Food and waterborne infections can also cause serious and sometimes chronic conditions. Examples include diseases caused by the parasite Toxoplasma gondii, and the bacteria Listeria monocytogenes, Clostridium botulinum, Yersinia enterocolitica and enterohaemorrhagic E. coli.

Since only a minority of disease cases are registered in MSIS at the NIPH, the medical and socioeconomic consequences of food and waterborne infections are far greater than the number of registered cases of disease would imply. 

Challenges and prevention

Norway has an over 100-year long tradition of targeted, effective combat of infectious disease agents among livestock together with an active food safety authority and restrictive import of meat, live animals and animal feed (NIPH, 2016d; Kapperud, 2015).

A number of serious infectious diseases that were previously common among Norwegian livestock are eradicated thanks to these measures, such as bovine tuberculosis, brucellosis, anthrax, trichinosis, salmonellosis and tapeworm infections. This has been instrumental to reduce the burden of disease in the human population.

Food and drinking water in Norway have never been safer in terms of incidence of infectious disease agents. However, some agents still have a significant prevalence in Norwegian livestock. This is particularly Toxoplasma in sheep and pigs, E. coli in sheep, Listeria in smoked, cured and fermented fish, Yersinia in pigs and Campylobacter in poultry, cattle, pigs and sheep.

In addition, we see a globalisation of the food market and an increase in both legal and illegal imports of food from countries where the burden of disease is greater than in Norway. Since foods are increasingly sold on an international market, the consequences of hygiene breaches can be far more extensive than before (NIPH, 2016d).

Water supply in Norway has special challenges because the population is scattered, with many small waterworks, extensive use of surface water and an urgent need for upgrading of the water supply network. We have limited information about how many people become ill from contaminated drinking water.

Other significant challenges in Norway are:

  • More food is prepared in commercial kitchens, so the consequences of hygiene breaches are larger than in single households.
  • Lack of knowledge about kitchen hygiene in the hospitality industry, health institutions and among the public (Jacobsen, 2011; Norwegian Food Safety Authority, 2009a, 2009b).
  • More organic, small-scale and local food production, where there can be problems in maintaining stable internal control.
  • More fast food.
  • Exotic foods are used by Norwegians in different ways to those in their production country, for example, herbs are consumed without heat-treatment.
  • Demographic changes: There are more elderly people and more people living longer with chronic diseases. In these groups there are many who are more susceptible to infection and have an increased risk of becoming seriously ill.
  • Increasing prevalence of antibiotic-resistant bacteria among meat-producing animals.

Preventive measures

The challenges can be met with preventive measures:

  • Improve small waterworks and upgrade old and poor water supply networks.
  • Maintain interdisciplinary collaboration that ensures food and waterborne infections, and infection between humans and animals are managed in an integrated perspective.
  • Monitor prevalence of infectious agents in animals, food and water.
  • Maintain good preparedness to detect and investigate cases of disease outbreaks and identify trends (NIPH, 2016h).
  • Monitor the incidence of food and waterborne infectious diseases in the population and carry out studies to determine the real burden of disease linked to infection from both water and food.



  1. Norwegian Institute of Public Health (NIPH). (2016a). Smittevernveileder for helsepersonell [Online publication, Norwegian only].  
  2. NIPH. (2016b). Norwegian Surveillance System for Communicable Diseases (MSIS). [database]. Extracted 20 September 2016.
  3. NIPH. (2016c). Utbrudd av smittsomme sykdommer i Norge i 2015: Vevbasert system for utbruddsvarsling (Vesuv) [Annual Report, Norwegian only]. 
  4. NIPH. (2016d). Sykdomsfremkallende mikrober, parasitter og prioner i næringsmidler (Online publication, Norwegian only). 
  5. NIPH. (2016e). Mat- og vannbårne infeksjoner 2015 (Årsrapport) [Annual report, Norwegian only]. 
  6. NIPH. (2016f). Oversikt over større utbrudd av smittsomme sykdommer i Norge og utlandet. [www.fhi.no]. Extracted 20 September 2016.
  7. NIPH. (2016g). Drikkevannsforsyning (LHF) − hygienisk kvalitet og leveringsstabilitet, tilfredsstillende analyseresultater. Norhealth Statistics bank [Database]. Extracted 1 October 2016.
  8. NIPH. (2016h). Utbruddsveilederen [Online publication, Norwegian only]. 
  9. Jacobsen, E., & Lavik, R. (2011). Kjøkkenpraksiser og mathygiene - litteraturgjennomgang og web-survey (Fagrapport 2011:3) [Report, Norwegian only]. Oslo: Norwegian Institute for Consumption Research (SIFO). 
  10. Kapperud, G. (2015). Næringsmiddelbårne infeksjoner og intoksikasjoner – Forekomst og betydning. I: P. E. Granum (red.), Matforgiftning: Smitte gjennom mat og vann (s. 22-35). [Book chapter, Norwegian only]. Cappelen Damm Akademisk.
  11. Norwegian Food Safety Authority. (2009a). Det er servert! - En tilstandsbeskrivelse av serveringsbransjen. Områdeanalyse av serveringsbransjen - delrapport 1 [Report, Norwegian only]. 
  12. Norwegian Food Safety Authority. (2009b). Institusjonskjøkken. Rapport - nasjonalt tilsynsprosjekt 2008-2009 [Report, Norwegian only].
  13. Schimmer, B., Nygard, K., Eriksen, H.-M., Lassen, J., Lindstedt, B.-A., Brandal, L., et al. (2008). Outbreak of haemolytic uraemic syndrome in Norway caused by stx2-positive Escherichia coli O103:H25 traced to cured mutton sausages. BMC Infectious Diseases, 8(1), 41. 


This article is a translation of the updated chapter in the Public Health Report. The statistics are based on the Norwegian Surveillance System for Notifiable Diseases (MSIS) and reports from the Norwegian Institute of Public Health. The Norwegian version was reviewed and updated in October 2016, with new MSIS statistics for 2015. The English version was first translated in January 2017.