Sludge Watch ==> Statement Foodborne Viral Infections - sewage, sewage sludge, contaminated water

[Maureen Reilly]

http://www.innovations-report.de/html/berichte/medizin_gesundheit/bericht-107117.html


Foodborne Viral Infections
08.04.2008


The Institute of Food Science & Technology has authorised the following 
Information Statement dated April 2008, which replaces the version issued in 
March 2002.



SUMMARY


Foodborne viral infections are caused mainly by two types of virus, 
norovirus (formerly named as Norwalk-like viruses (NLV) or small round 
structures viruses (SRSVs)) which cause gastroenteritis and Hepatitis A 
virus which causes hepatitis. All foodborne viruses originate from the human 
intestine and contamination of food occurs either by contamination from an 
infected food handler during preparation or by contact with sewage, sewage 
sludge or polluted water. Control measures mainly depend on staff education 
and good factory and kitchen hygiene; food handlers suffering from symptoms 
should be excluded from work immediately and all staff made aware of the 
ease with which viral contamination is transmitted. The use of clean water 
for irrigation of crops that are likely to be eaten raw and cultivation of 
molluscan shellfish in sewage-free seawater are also essential to prevent 
viral contamination of food.

THE PROBLEM

Foodborne viruses are a common and, probably, the most under-recognised 
cause of outbreaks of gastroenteritis. Human infection can occur following 
consumption of contaminated food, person-to-person body contact, or release 
of aerosols. Food may be contaminated by infected food handlers or by 
contact with water contaminated by treated or untreated sewage. Outbreaks of 
viral foodborne illness have been associated with the consumption of 
shellfish that have been harvested from sewage-polluted waters. The greatest 
risk of foodborne illness occurs with catering operations preparing ready to 
eat foods, although foodborne spread is difficult to prove.

VIRAL FOODBORNE ILLNESS

The types of foodborne virus fall into two main groups:

(1)Norovirus (formerly named Norwalk-like viruses (NVLs) or small round 
structured viruses (SRSVs)) which cause gastroenteritis;

(2)Hepatitis A virus, which causes hepatitis.

Norovirus

Illness caused by norovirus is usually sudden in onset and characterised by 
vomiting, diarrhoea and abdominal pain. Vomiting frequently occurs without 
warning and may be projectile and uncontrollable, whilst diarrhoea may be 
explosive. The incubation period is usually 24 - 36 hours after eating an 
implicated food but may be from 15 - 72 hours, depending on the number of 
virus particles consumed. The duration of the symptoms varies from 12 - 72 
hours but, after the initial uncontrollable onset, the symptoms may be 
relatively mild. Despite this, sufferers may feel debilitated for 2-3 weeks.

Very few virus particles are needed to cause illness, so the attack rate in 
an outbreak can be very high, with the majority of people who ate the 
contaminated food becoming ill. Because the viruses multiply in the gut, a 
very large number of virus particles are excreted during the illness (often 
more than 10 million per gram of faeces or vomitus). As a result of the 
uncontrollable nature of the symptoms, food can easily become contaminated 
by infected food handlers and secondary person-to-person spread is also 
common.

Hepatitis A

Viral hepatitis has a long incubation period of 3 - 6 weeks, with symptoms 
developing gradually. Symptoms include loss of appetite, malaise, fever and 
vomiting, followed by jaundice. Illness usually lasts a few weeks but may 
last several months, and is usually more severe in adults than in children. 
Death may occur, particularly in the elderly, but is very rare. Large 
numbers of virus particles can be shed in the urine and faeces during the 
latter part of the incubation period, before jaundice is apparent, but they 
are usually absent one week after the onset of jaundice.

SOURCE

Viruses require a host in order to multiply, and the original source of all 
foodborne viruses is the human intestine. They cannot grow in food. 
Contamination of food may occur either during preparation and serving by 
infected food handlers or by contact with sewage or sewage-polluted water.

The main food type associated with foodborne viruses is molluscan shellfish 
such as oysters, cockles and mussels, which are usually found in shallow 
coastal or estuarine waters, commonly near sewage outlets. These shellfish 
are filter feeders that can concentrate virus particles from the surrounding 
water. Molluscs are either eaten raw or after a mild heat process, which if 
poorly controlled may not inactivate virus particles present. Shellfish 
harvesting areas are classified according to the level of faecal indicator 
bacteria present in the shellfish flesh; if the levels exceed the 
specification for direct consumption, the shellfish must be relayed in 
cleaner water, receive an approved heat treatment or undergo a purification 
process (depuration) before sale. However, depuration cannot be guaranteed 
to remove viruses, and outbreaks of viral gastroenteritis have been 
attributed to depurated shellfish. Cultivation of molluscan shellfish in 
water protected from sewage contamination is therefore paramount in the 
control of viral infection.

Although molluscs are the most clearly implicated source of foodborne viral 
illness, they do not necessarily cause most illness.

Fruit and vegetables may act as vehicles of infection if fertilized with 
sewage sludge or irrigated with sewage-contaminated water. Guidelines issued 
by the World Health Organisation (WHO) state that fruit and vegetables 
intended to be eaten raw should not be fertilized with sewage or irrigated 
with contaminated water. Apart from an outbreak of Hepatitis A resulting 
from contaminated soft fruit, there are no proven outbreaks associated with 
contamination of these foods at source. Control of sewage sludge application 
to land is important to prevent viral (and other pathogens) being recycled 
to affect human and animal health. In the UK, the Sewage (Use in 
Agriculture) Regulations 1989 are designed to protect the environment and 
human and animal health where sewage sludge is used on agricultural land. A 
“Safe Sludge Matrix” (ADAS, 2001) recommends the minimum time periods 
between the application of sludges to land and its use for food production 
and includes a table of crop types, together with clear guidance on the 
minimum acceptable level of treatment for any sewage sludge (often referred 
to as biosolids).

Contamination of food by infected food handlers is an important cause of 
viral foodborne illness. Food items such as salads and dessert dishes that 
receive considerable handling during preparation and are not given any 
further heat treatment before consumption are often implicated in foodborne 
viral outbreaks. Consumption of contaminated water and ice, or their use in 
food preparation, has also caused viral illness.

DETECTION

Detection of viruses in food has not been considered possible in a routine 
laboratory because of their requirement for a living host or animal tissue 
for growth. In addition, the level of virus particles in a contaminated food 
is usually very low. Specialist laboratories may achieve detection using 
cell culture and complex extraction methods but techniques previously 
available are not suitable for routine application and recovery rates remain 
poor. The use of the polymerase chain reaction (PCR) is being developed for 
detection of norovirus in foodstuffs implicated as the source of outbreaks. 
A recent method, said to give results in under 4 hours, involves 
recirculating-IMS linked to PCR (paper on inter-laboratory trials awaiting 
publication).

Methods currently used for routine detection of NLVs in faeces are based on 
immunoassays and PCR. Ideally, samples should be collected within 48 hours 
of the onset of symptoms since these contain the greatest levels of the 
virus. Use of this PCR test enables the detection of more than 90% of NLV 
infections and also allows characterization of the strains.

Detection of Hepatitis A virus in faeces is not usually possible because, by 
the time jaundice occurs, the peak of excretion of virus particles has 
passed. Diagnosis is based on detection of specific IgM and IgG antibodies 
in the blood serum or saliva.

SURVIVAL CHARACTERISTICS

Foodborne viruses are hardy and may survive for prolonged periods in foods 
or the food handling environment as well as persisting in aquatic 
environments. They are highly resistant to chilling, freezing, preservatives 
and ionising radiation. Hepatitis A virus and norovirus have both been shown 
to survive 60°C for 10 minutes. However, inactivation of these viruses 
occurs at temperatures above 65°C at a rate proportional to the temperature 
but also depends on the composition of the medium. Both agents are killed by 
boiling. They are resistant to acidic conditions (pH 3) and can therefore 
survive on acid fruits such as strawberries and raspberries and in processes 
such as pickling in vinegar or yogurt production. They are also resistant to 
alcohol and high sugar concentrations.

MANAGEMENT OF FOOD HANDLERS

Food handlers suffering from vomiting or diarrhoea should be excluded from 
work immediately. They should not return to work until at least 48 hours 
after cessation of symptoms. After the initial onset of symptoms, although 
infection may appear to be sufficiently mild to enable the food handler to 
continue working, this must be prevented since even very low numbers of 
norovirus can result in illness if transferred to the food. Prevention of 
foodborne viral illness requires good staff supervision and food handlers 
should be encouraged to report symptoms of illness as soon as they occur. 
Staff should also be made aware that they could transfer viral contamination 
to food via hands and clothing following contact with an ill family member. 
There is no carrier state associated with norovirus although some patients, 
particularly children, may be asymptomatic. .

Hepatitis A is mainly spread by person-to-person transmission but can be 
spread by food handlers. Cases of viral hepatitis are most infectious before 
jaundice is apparent, but exclusion of food handlers from work for one week 
after the onset of jaundice is recommended. There is no chronic carrier 
state. If food handlers are exposed to Hepatitis A, those shown not to be 
immune by antibody testing may be vaccinated or given prophylactic human 
normal immunoglobulin by injection. Children can show very mild or 
asymptomatic infection.

CONTROL

Shellfish are an important cause of viral gastroenteritis. Cultivation in 
clean waters is very important, as depuration procedures may not be 
effective in eliminating viruses. Heat treatment to an internal temperature 
of 85°C - 90°C, maintained for 90 seconds, is required to destroy viruses 
in molluscs but careful control is necessary to achieve this without 
toughening of the shellfish flesh. Consumption of uncooked molluscs such as 
oysters remains a risk, as is cross-contamination from contaminated 
shellfish to other food in the kitchen.

Contamination of foods other than shellfish will normally occur on the 
surface of the food, where viruses will be more susceptible to heat 
treatment. Heat processes commonly used in the food industry, such as 
heating to a core temperature of 70°C for two minutes, will significantly 
reduce the level of virus contamination but may not destroy all the viruses 
if the contamination level was very high.

The number of virus particles required to cause infection is very low. 
Contamination of food with norovirus by infected food handlers and 
person-to-person spread occurs easily due to the very large numbers of virus 
particles present in the stools and vomitus at the onset of symptoms, and to 
the survival characteristics of the viruses. Infection of personnel may take 
place by aerosol inhalation and subsequent ingestion as well as the 
hand-to-mouth route. Thorough hand washing with soap and warm running water 
and drying with disposable towels or air hand dryers are essential to 
minimize spread of contamination.

If vomiting has occurred in the kitchen or factory, a rigorous and 
appropriate disinfection for viral decontamination of the environment must 
be implemented. This is best achieved by cleaning, using hot water and 
detergent, followed by disinfection with a chlorine-based disinfectant at a 
concentration of 500 ppm available chlorine. Food that may have been exposed 
to aerial contamination or handled by the ill person should be destroyed 
unless it is to be heated above a core temperature of 85°C following 
exposure. If contaminated food is not destroyed, cross-contamination and 
re-infection may occur. Any soiled clothing should be rinsed to remove gross 
contamination, preferably into the toilet bowl, and then laundered in a 
domestic or commercial washing machine with a hot cycle (above 85°C).

OTHER FOODBORNE VIRAL INFECTIONS

Norovirus is not the only virus that can cause diarrhoeal illness. Although 
many of these viruses are transmitted via person to person, especially 
during childhood, they can also be transmitted via food handlers as well as 
by sewage contamination of drinking water, shellfish, fruit, vegetables and 
salad products. These viruses include aichivirus, rotavirus, sapovirus, 
parvovirus and astrovirus. As with norovirus, there is, to varying degrees, 
evidence for environmental robustness which allows survival on dry surfaces, 
in food matrices and in water (including sea water). However, all are killed 
by boiling.

Hepatitis A virus is not the only cause of foodborne hepatitis, which can 
also be caused by Hepatitis E virus. The clinical features of infection are 
similar to Hepatitis A, although the incubation period for infection is 
often longer (mean 40 days, range 15 - 60 days) and the disease is more 
severe. The case fatality rate is 0.1-1%. Hepatitis E can cause 
life-threatening infections in women in the later stages of pregnancy, with 
case fatality rates approaching 20%. The incidence of Hepatitis E is highest 
in developing countries in tropical or subtropical areas of the world with 
inadequate environmental sanitation. Most disease presents as endemic or 
sporadic cases although major epidemics do occur affecting tens of thousands 
of patients. The primary source of Hepatitis E infection appears to be 
faecal contamination of water and epidemic outbreaks are often preceded by 
periods of heavy rain which lead to contamination of water supplies with 
untreated sewage. Food-borne transmission occurs uncommonly and 
person-to-person transmission is rare. Hepatitis E infections do occur in 
developed countries and, although usually associated with travel to endemic 
regions, recent studies have identified cases with no history of recent 
foreign travel (termed autochthonous), often with links to either contact 
with pigs or the consumption of pig meat. Certainly, Hepatitis E is endemic 
in British pigs and several human cases have been shown to be infected with 
virus strains similar to those found in pigs.

IMPLICATIONS FOR THE FOOD INDUSTRY

The prevention of foodborne viral illness depends on the quality of raw 
materials, staff education and a high level of awareness in the 
manufacturing and catering industries. If payment is withheld during 
sickness, staff will be reluctant to cease working when symptomatic. 
However, the cost of sickness benefit is minimal compared with the potential 
costs incurred as a result of a foodborne outbreak.

FURTHER READING

ADAS (2001). “Safe Sludge Matrix” 3rd Ed. 
http://www.adas.co.uk/media_files/Publications/SSM.pdf

Carter MJ. (2005). Enterically infecting viruses: pathogenicity, 
transmission and significance for food and waterborne infection. J App 
Microbiol; 2005; 98:1354-80.

Regulation (EC) No 853/2004 laying down specific hygiene rules for food of 
animal origin, Annex III, Section VII. OJ L226: 25.6.2004, pp22-82 (as 
amended). 
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:2004R0853:20070101:en:pdf

Koopmans, M and Duizer, E. “Foodborne viruses: an emerging problem?” 
ILSI Europe (Sept 2002). 
http://europe.ilsi.org/publications/Report+Series/FoodborneViruses.htm

Mara, D. and Cairncross, S. (1991). Guidelines for the safe use of 
wastewater and excreta in agriculture and aquaculture. WHO: Geneva. 
www.who.int/water_sanitation_health/medicalwaste/130to134.pdf

Viral Gastroenteritis Sub-Committee of PHLS Virology Committee (1993). 
Outbreaks of gastroenteritis associated with SRSVs. PHLS Microbiology Digest 
10: 2-8.

Working Party of the PHLS Salmonella Committee (1995). The prevention of 
human transmission of gastrointestinal infections, infestations, and 
bacterial intoxications. Communicable Disease Report 5: Review No.11, R158 - 
R172.
www.hpa.org.uk/CDR/archives/CDRreview/1995/cdrr1195.pdf

UK Statutory Instrument 1989 No. 1263. The Sludge (Use in Agriculture) 
Regulations 1989. HMSO, London. 
http://www.opsi.gov.uk/si/si1989/Uksi_19891263_en_1.htm


Notes for editor
The Institute of Food Science & Technology (IFST) is the independent 
professional qualifying body for food scientists and technologists. It is 
totally independent of government, of industry, and of any lobbying groups 
or special interest groups. Its professional members are elected by virtue 
of their academic qualifications and their relevant experience, and their 
signed undertaking to comply with the Institute's ethical Code of 
Professional Conduct. They are elected solely in their personal capacities 
and in no way representing organisations where they may be employed. They 
work in a variety of areas, including universities and other centres of 
higher education, research institutions, food and related industries, 
consultancy, food law enforcement authorities, and in government departments 
and agencies. The nature of the Institute and the mixture of these 
backgrounds on the working groups drafting IFST Information Statements, and 
on the two Committees responsible for finalising and approving them, ensure 
that the contents are entirely objective. IFST recognises that research is 
constantly bringing new knowledge. However, collectively the profession is 
the repository of existing knowledge in its field. It includes researchers 
expanding the boundaries of knowledge and experts seeking to apply it for 
the public benefit.

Competence, integrity, and serving the public benefit lie at the heart of 
IFST philosophy. At all times IFST aims to:

• Benefit the public supply of safe, wholesome, nutritious, tasty and 
attractive food through the application of sound science and technology;

• Improve public knowledge and awareness of important issues relating to 
the production, safety and quality of food;

• Develop and communicate the knowledge underlying food science and 
technology, and further the education of food scientists and technologists;

• Safeguard the public by defining, promoting, and upholding professional 
standards of competence, integrity and ethical behaviour; and

• Maintain these standards by encouraging members to continue their 
professional education and development throughout their careers.

In serving the public benefit IFST takes into account the many elements that 
are important for the efficient and responsible supply, manufacture and 
distribution of safe, wholesome, nutritious, and affordable foods with due 
regard for the environment, animal welfare and the rights of consumers.


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liability whatsoever in connection with them. Nothing in them should be 
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are provided for general information and guidance and to express expert 
interpretation and opinion, on important food-related issues

Neville Craddock