Foodborne Viruses – Definition, Examples, Detection, Prevention

What are foodborne viruses?

Foodborne viruses are those that can be contracted by eating or drinking contaminated food or water. They can withstand extremes in temperature and humidity as well as hostile conditions like low pH (acidity). Because of this, they can survive infectively in food and water for much over a month. These viruses are primarily transmitted by feces and other bodily fluids because they are shed in the intestines of infected humans and animals. Oftentimes, unclean production methods or accidental contact with animal waste or sewage are to blame for pathogenic viral contamination of food products.

The most prevalent sources of foodborne viruses include shellfish caught near human sewage outlets, undercooked meats, and fruits and vegetables cultivated on soil treated with animal excrement. Even if sewage systems are cleaned, the amount of viruses that can be removed and how effectively they can be removed rely on the viral load that is already there.

• Illnesses caused by foodborne viruses occur when an individual consumes tainted food or water. Fruits, vegetables, shellfish, meat, and poultry are all susceptible to infection from these viruses.
• Norovirus, hepatitis A virus, and rotavirus are just a few examples of food-borne viruses. The norovirus can spread rapidly and produce severe stomach cramps, vomiting, and diarrhea. Inflammation of the liver is a common complication of having the hepatitis A virus. Children’s diarrhea is often caused by rotavirus.
• There are many potential vectors for the transmission of food-borne viruses, including unsanitary conditions, polluted water or soil, and careless or unsafe food preparation. Dehydration, nausea, vomiting, diarrhea, and fever are all possible outcomes of a virus contracted from eating contaminated food.
• Cleaning your hands thoroughly before handling food, cooking to the right temperatures, and storing food at safe temperatures are all important steps in preventing the spread of foodborne viruses. Furthermore, commercial food outlets can do their part to stop the spread of foodborne viruses by adhering to rules and having regular inspections for food safety.
• The most frequently reported symptoms of foodborne viruses are gastroenteritis and hepatitis. Although many different varieties of gastrointestinal viruses can be found in humans, gastroenteritis caused by the human norovirus and hepatitis A virus (HAV) is the most commonly reported type of gastroenteritis associated with foodborne viruses.
• Other viruses, such as enterovirus, sapovirus, rotavirus, astrovirus, adenovirus, and Hepatitis E virus, have also been linked to dietary and waterborne transmissions.
• The norovirus causes gastroenteritis, which is characterized by diarrhea, vomiting, fever, migraines, and abdominal pain. Campylobacter, which is associated with raw or undercooked food, Salmonella, which is typically found in meat or eggs, and Listeria, which can be present in prepared foods, are all bacterial causes of gastroenteritis.
• They cause symptoms like diarrhea, vomiting, and fever, but can also cause life-threatening conditions and mortality.

Sources of Contamination

Foodborne viruses can be transmitted through a variety of sources, including:

1. Infected food handlers: Viral contamination of food can occur through the poor hygienic practices of infected food handlers who fail to wash their hands thoroughly before handling food.
2. Fecal pollution: Fecally polluted water that flows into farmlands can contaminate crops and produce items. Shellfish can also accumulate viruses in their gastrointestinal tract.
3. Contact with contaminated surfaces: Viruses can survive on surfaces such as kitchen counters, utensils, and equipment, and can contaminate food if not properly sanitized.
4. Person-to-person transmission: Viral infections can be transmitted from an infected person to others, and if food is prepared or served by an infected person, it can lead to the spread of the virus.
5. Aerosols: Some viruses can spread through the air and can contaminate food if it is not properly protected.
6. Improper food handling and preparation: Food that is not cooked or stored at the correct temperature can be a breeding ground for viruses.
7. Animal waste: Animal waste in the environment can also contaminate crops and produce items.

Preventing contamination of foodborne viruses requires proper food handling and preparation techniques, such as washing hands thoroughly before handling food, cooking foods to their recommended temperatures, and storing foods at safe temperatures. Additionally, food safety regulations and inspections can help prevent the spread of foodborne viruses in commercial food establishments.

Foodborne viruses Examples

Foodborne viruses that can cause illness in humans include:

1. Norovirus: The most common cause of foodborne illness, responsible for 58% of foodborne illnesses in the United States. It can cause symptoms such as vomiting, diarrhea, and stomach cramps.
2. Hepatitis A virus (HAV): Causes inflammation of the liver and can be transmitted through contaminated food and water. Symptoms include fever, nausea, and abdominal pain.
3. Rotavirus (RV): Causes severe diarrhea and can be particularly dangerous for infants and young children.
4. Hepatitis E virus (HEV): Similar to HAV, it can cause liver inflammation and is transmitted through contaminated food and water.
5. Adenovirus (AdV): Can cause respiratory and gastrointestinal illnesses and is spread through contact with contaminated surfaces or through the air.
6. Sapovirus: Causes similar symptoms to norovirus and is spread through contaminated food and water.
7. Astrovirus: Can cause diarrhea and is spread through contact with contaminated surfaces or through the air.
8. Aichi virus (AiV): Can cause gastroenteritis and is spread through contaminated food and water.
9. Parvovirus: Can cause respiratory and gastrointestinal illnesses and is spread through contact with contaminated surfaces or through the air.

It is important to note that there are many other types of viruses that can cause foodborne illness, and new ones may emerge in the future.

Human Noroviruses

• An significant human disease that may cause both isolated instances and widespread epidemics, noroviruses are classified into numerous serologically distinct families that have been given names based on the locations where they first appeared in nature.
• The icosahedral viral particles are between 27 to 30 nm in size, and they harbor a single-stranded, positive-sense RNA genome.
• Replication occurs in the small intestine, leading to temporary lesions of the intestinal mucosa and possible disease of peripheral tissues after oral intake of contaminated food or water. Aerosols released when someone vomits and fomites like shared items can also spread disease.
• The condition is self-limiting, lasting anywhere from 12 hours to 3 days, depending on the individual, and requires just a minimal infection dosage of 10 to 100 virus particles. Symptoms include nausea, vomiting, diarrhoea, myalgias, and abdominal discomfort.
• Asymptomatic patients and those with compromised immune systems may experience prolonged viral shedding of up to 8 weeks. Some people have headaches and mild fevers when infected with Norovirus, and anecdotal evidence suggests that the virus may be responsible for other disorders, such as baby necrotising enterocolitis.
• Direct transmission occurs between humans via feces and vomit, while indirect transmission occurs via ready-to-eat foods (including leafy vegetables, herbs, berries, and meals touched after cooking), water, and the environment.
• Healthcare-associated infections are very widespread in Europe. Up to 24% of worldwide outbreaks6 have food as a possible cause. In 2016, the most common foods linked to norovirus outbreaks across Europe were vegetables and juices, as well as seafood, shellfish, and mollusk products.

Hepatitis A virus

• Similar to HNoVs, HAV of the Picornaviridae family is a positive-sense, single-stranded, nonenveloped RNA virus ranging in size from 27 to 32 nm. Unlike HNoVs, the genome is 7.5 kb in length and consists of a single ORF.
• Three main viral structural capsid proteins, VP1, VP2, and VP3, are encoded in the P1 region of the genome. P2 and P3 regions encode the proteins necessary for RNA replication and virion formation. To date, only one serotype of HAV has been identified, and it has been reported that a single exposure confers lifelong immunity.
• However, the genetic diversity of populations across the globe led to their classification into seven genotypes, designated I–VII, which are known to infect either humans or simians. In 1988, Halliday et al. reported the largest foodborne viral outbreak, in which 292 301 cases of HAV were attributed to consuming raw clams in Shanghai, China.
• In contrast to the brief incubation period of HNoVs, the average incubation period of HAV is approximately 28 days, with severe symptoms that can last between 4 and 6 weeks, including jaundice, dark urine, vomiting, fever, and weight loss.
• Infection is typically symptomatic for two months in older children and adults, with jaundice occurring in 70% of patients. The first phase is the asymptomatic incubation phase, which lasts for 10–50 days, followed by three symptomatic phases: the preicteric phase, which lasts several days to weeks and is characterized by fatigue, nausea, loss of appetite, fever, dark urine, diarrhea, and pale stools; the icteric phase with jaundice; and the convalescent phase.
• There are only a few HAV strains that can adapt to cell culture. These strains cause cell demise through cytopathic effects and are therefore used in research involving survival and inactivation studies.
• Several research groups have reported that HAV remains infectious in mineral water stored at room temperature for 10 months, after a month at ambient temperatures on environmental surfaces, for >4 hours on hands, during prolonged storage of spinach leaves at 5.4 degrees Celsius, and on romaine lettuce leaves after 12 days in a sealed-atmosphere plastic package at 4 degrees Celsius.
• Researchers also report that HAV can persist at a pH of 3.75 for four weeks and at pH 1.0 for five hours and sixty minutes at 60 degrees Celsius.
• The literature indicates that HAV is inactivated in bivalve after heating at 85–90 degrees Celsius for 1.5 minutes and at 450 MPa hydrostatic pressure for 5 minutes. These survival characteristics play an important role in HAV transmission.

Hepatitis E Virus

• HEV is a small, non-enveloped, single-stranded positive-sense RNA virus with a size range of 32–34 nm that is primarily transmitted via the fecal–oral route, typically via contaminated water.
• The genome of the Hepevirus genus member of the Hepeviridae family contains three ORFs. ORF1 encodes a nonstructural polyprotein that is composed of helicase, protease, and RNA-dependent RNA polymerase.
• ORF2 encodes the capsid protein, while ORF3 encodes a phosphoprotein involved in replication and cytoskeleton synthesis. Four HEV genotypes have been identified to date, with genotypes 1 and 2 affecting humans and genotypes 3 and 4 affecting pigs.
• According to reports, the average incubation period for HEV infection is between two and ten weeks, with two distinct phases of illness. The preicteric phase is characterized by fever, anorexia, vomiting, and abdominal pain, whereas the icteric phase is self-limiting and characterized by bilirubin.
• Reported viral dissemination occurs 1–2 weeks before and 2–4 weeks after the onset of symptoms. Serum alanine aminotransferase and aspartate aminotransferase levels rise significantly, which can be used to detect liver damage.
• Due to its lengthy incubation period, the association between HEV and specific foods has not been conclusively established; however, recent studies have linked HEV gt3 transmission to the consumption of raw porcine meat.
• For the relief of HAV symptoms, there is no specific treatment besides the patient care described earlier in the text. It has been reported that administering PEGylated interferon for chronic infections has moderate efficacy. Vaccine trials are being examined in order to ascertain preventative measures.

Rotavirus

• By electron microscopy, RVs of the family Reoviridae can be distinguished from HNoVs and HAVs by their multilayered icosahedral capsids that range in size from 60 to 100 nm. The RV genome consists of 11 segments of double-stranded RNA that code for structural (VP1–VP8) and nonstructural (VP9–VP12) proteins.
• These proteins compose the mature virus’s multilayered capsid, which encases the genome. The complete virion is a particle with three layers and is infectious. VP7 and VP4 structural proteins compose the exterior core layer.
• Seven RV groups, ranging from A to G, have been identified, with groups A, B, and C being linked to human infections and genotypes G1P8, G2P4, G3P8, G4P8, and G9P8 being the most frequently identified worldwide.
• In children younger than 5 years, RV is a frequent cause of acute gastroenteritis. RV was first identified by Bishop et al. using electron micrographs of intestinal and stool biopsies from pediatric gastroenteritis patients, which revealed a typical wheel shape, hence the Latin name ‘rota’, which means wheel.
• Reportedly, the incubation period for human RV is between 1 and 3 days. The symptoms reported 48 hours after RV infection include diarrhea with mucus, abdominal discomfort, vomiting, and dehydration, with severe diarrhea resulting in high global mortality rates.
• In the 1980s, there were 870 000 deaths linked to RV infection globally, with current numbers around 450 000 per year; developing countries such as the Democratic Republic of the Congo, Ethiopia, India, Nigeria, and Pakistan accounted for more than half of total RV-related deaths, with India accounting for 22 percent (98 621 deaths) of deaths. It is known that contaminated water, unhygienic practices, and unsanitary conditions cause numerous RV outbreaks.
• It has also been reported that human RV survives and retains its antigenicity after 60 minutes of exposure to 5 mg ml1 of chlorine. Researchers have reported that heating at moist (100 C) and dry (60 C) conditions for 1–20 minutes and high-pressure processing (HPP) at 350 MPa at 4 C have some effect on RV titers.
• Literature reports that commercial cranberry and grape beverages at their native pH as well as natural substances such as persimmon extract and wattle extract (0.5% solution) can also reduce RV titers.
• The development of animal model systems for the study and improvement of strategies for protection against infection by diverse RV serotypes/isolates. Two Simian RV strains, SA11 and Rhesus rotavirus (RRV), are used as reference strains globally, and it is reported that some of the presently available reassortment vaccines are based on the RRV strains.
• As a preventative measure against RV infection in humans, the World Health Organization recommends vaccination, which has reportedly substantially reduced gastroenteritis and mortality associated with RV.

Aichi Virus

• Yamashita et al. reported that AiV of the genus Kobuvirus in the family Picornaviridae was first isolated in 1989 from patient stool samples during a gastrointestinal outbreak involving oysters in Aichi, Japan.
• AiV virions are icosahedral with a diameter of 30 nm and three capsod proteins. AiV possesses a positive-sense, single-stranded RNA with a poly(A) tail and a single ORF encoding for structural proteins VP0, VP1, and VP3.
• There are six nonstructural proteins: 2A, 2B, 2C, 3A, 3B, 3C, and 3D. As A–C, three distinct AiV genotypes have been identified. Cases of AiV-associated gastroenteritis have been reported from Asia, Africa, Europe, and South America, indicating its geographic distribution and prevalence.
• AiV has been shown to survive (without reduction) HPP treatment at 600 MPa for 5 minutes, heating at 50 and 60 C for 30 minutes, 10% chloroform, and MEM (pH 3.5) for 3 hours.
• However, 240 mW s cm2 of ultraviolet light treatment has been reported to partially inactivate AiV, and some researchers have suggested that it may be beneficial for reducing AiV on fresh produce such as strawberries, green onions, and lettuce.

Sapovirus

• Sapovirus is an RNA virus with a positive sense that infects humans and swine.
• In 1977, the human sapovirus Sapporo virus (SaV) was first identified in Japan.
• Sapoviruses are separated into five genogroups, with GI, GII, GIV, and GV infecting humans, and GIII infecting swine.
• SaV epidemics are less common than those caused by human norovirus (HNoV), but they have increased in confined populations such as schools, hospitals, and hotels.
• Infection with SaV causes fever, diarrhea, nausea, abdominal pain, shivers, and malaise, with an incubation period of 24-48 hours on average.
• Human SaVs and HNoVs cannot be cultured at this time, but porcine sapovirus (Cowden strain) can be cultured in LLC-PK kidney cell line from pigs.
• The similar resistance of porcine SaV and HNoV to heat, sodium hypochlorite, and a pH range of 3.0 to 8.0 makes porcine SaV a useful surrogate for investigating HNoV.

Adenoviruses

• Adenoviruses (AdV) are 90-100 nm in size, double-stranded DNA viruses that can cause respiratory disease.
• There are 52 human AdV serotypes, divided into six species: A to G.
• Acute gastroenteritis is associated with subgenus F (AdV types 40 and 41) and subgenus A (AdV types 12, 18, and 31).
• After RV, HAdV serotypes 40 and 41 are the second most common viral cause of gastroenteritis in children.
• Symptoms of HAdV infections include upper and lower respiratory tract infections, pneumonia, conjunctivitis, gastroenteritis, and urinary tract infections.
• After an incubation period of 8-10 days, gastroenteritis symptoms include diarrhea, vomiting, dehydration, and fever, which last for 7-8 days.
• Infections with HAdV are typically moderate and self-limiting, but they can cause severe clinical manifestations like cystitis, enteritis, encephalitis, and pneumonia.
• HAdV can discharge for up to 7-14 days following infection.

Astroviruses

• Astroviruses are 30 nanometer in diameter, star-shaped, envelopeless, single-stranded, positive-sense RNA viruses.
• They were first identified in England in infants with diarrhea.
• Astroviruses are members of the family Astroviridae, which consists of two genera: Mamastrovirus (infecting mammals) and Avastrovirus (infecting birds).
• Human astroviruses (HAstV) are reported to have eight known serotypes, with type 1 being the most prevalent.
• HAstVs are further classified into two genogroups, A and B. Genogroup A consists of serotypes 1–5 and 8, while Genogroup B consists of serotypes 6 and 7.
• After 2–3 days of infection, HAstV is a common cause of gastroenteritis in children.
• Astrovirus is known to persist for extended periods in the environment, including water and surfaces for 60 days at 4°C and in water for 20°C, and is resistant to 1 mg l-1 of free chlorine.
• There is little evidence of AdV and astrovirus transmission through food.

Parvovirus

• Parvovirus is an 18-26 nM-sized, 5 kb unenveloped, single-stranded DNA virus.
• It was identified in 1974 during testing for hepatitis B.
• Based on transcription maps, terminal repeats, and mode of replication, three genera are recognized: Parvovirus, Dependovirus, and Erythrovirus
• Dependovirus and Erythrovirus are the only human pathogens.
• The Parvovirus genome contains two open reading frames (ORFs) that code for viral proteins VP1 and VP2 and nonstructural proteins.
• Parvoviruses are resistant to a pH range of 3 to 9 and temperatures of 56 °C for 60 minutes, but they are susceptible to formalin and gamma radiation.
• Parvoviruses have been linked to shellfish and milk outbreaks.
• The “cockle agent” parvovirus caused a significant outbreak in the United Kingdom due to contaminated cockles.
• Milk that has been properly cooked and pasteurized has decreased the transmission of these viruses.

Toroviruses

• Toroviruses of the family Coronaviridae and genus Torovirus are positive, single-stranded RNA viruses (28 kb in length) ranging in size from 100 to 150 nM.
• Human toroviruses have been isolated from the feces of infants and adults with diarrhea. Bovine, equine, and porcine toroviruses are also known. Unknown is their function in human foodborne gastroenteritis.

Picornaviruses

• Picornaviruses of the Birnaviridae family are 35 nM, RNA viruses that are associated with gastroenteritis in HIV-infected immunocompromised patients and have been detected in humans with and without diarrheal symptoms.
• The function of these viruses and toroviruses in food-borne gastroenteritis in humans is still unknown.

Epidemiology of Foodborne viruses

Foodborne viruses are a major public health concern worldwide, causing a significant number of illnesses, hospitalizations, and deaths each year. Here are some key epidemiological facts about foodborne viruses:

1. Incidence: According to the World Health Organization (WHO), foodborne illnesses affect an estimated 600 million people globally each year. Of these cases, approximately 40% are attributed to contaminated food.
2. Norovirus: Norovirus is the most common cause of foodborne illness worldwide, responsible for an estimated 685 million cases each year.
3. Hepatitis A virus: Hepatitis A is a common foodborne virus, particularly in developing countries with poor sanitation. According to the WHO, there were an estimated 1.5 million cases of hepatitis A worldwide in 2016.
4. Rotavirus: Rotavirus is a common cause of gastroenteritis in young children, responsible for an estimated 215,000 deaths each year.
5. High-risk groups: Certain populations are at higher risk of developing severe illness from foodborne viruses, including young children, elderly individuals, pregnant women, and people with weakened immune systems.
6. Outbreaks: Foodborne virus outbreaks are not uncommon and can affect large numbers of people. Outbreaks are often associated with contaminated foods such as fresh produce, shellfish, and ready-to-eat foods.
7. Prevention: Preventing foodborne virus infections requires a multi-faceted approach that includes improving sanitation practices, implementing food safety regulations, educating the public about safe food handling practices, and conducting surveillance to monitor outbreaks and identify emerging viruses.

Understanding the epidemiology of foodborne viruses is critical to developing effective strategies for preventing and controlling these infections.

Clinical manifestation during viral infection

Clinical manifestations during viral infections can vary depending on the type of virus and the individual’s immune response. Here are some common clinical manifestations of viral infections:

1. Fever: Fever is a common symptom of viral infections and is a sign that the body is trying to fight off the infection.
2. Headache: Headaches are a common symptom of many viral infections, including the common cold and flu.
3. Fatigue: Fatigue and weakness are common symptoms of viral infections and can last for several days or even weeks.
4. Respiratory symptoms: Many viral infections can cause respiratory symptoms such as cough, sore throat, and shortness of breath.
5. Gastrointestinal symptoms: Some viral infections can cause gastrointestinal symptoms such as nausea, vomiting, and diarrhea.
6. Skin rash: Certain viral infections, such as measles and chickenpox, can cause a skin rash.
7. Neurological symptoms: Some viral infections can cause neurological symptoms such as seizures, confusion, and paralysis.

It’s important to note that not everyone infected with a virus will experience all of these symptoms, and some individuals may have no symptoms at all. The severity of symptoms can also vary depending on the individual’s age, overall health, and immune response to the virus.

Detection Methods of Foodborne viruses

There are several methods available for the detection of foodborne viruses, including:

• Molecular methods: Molecular methods such as polymerase chain reaction (PCR) and real-time PCR are commonly used for the detection of foodborne viruses. These methods can detect viral nucleic acid in food samples with high sensitivity and specificity.
• Immunological methods: Immunological methods such as enzyme-linked immunosorbent assay (ELISA) and lateral flow assays are commonly used for the detection of viral antigens or antibodies in food samples.
• Cell culture: Viral culture methods can be used to isolate and identify viruses in food samples, but these methods are time-consuming and require specialized facilities and expertise.
• Next-generation sequencing: Next-generation sequencing (NGS) technologies can be used for the identification and characterization of viral genomes in food samples.
• Biosensors: Biosensors that use electrochemical, optical, or magnetic transducers to detect viral particles or viral antigens are being developed as rapid and sensitive methods for the detection of foodborne viruses.

It is important to note that each method has its advantages and limitations, and the choice of method depends on the specific needs of the investigation, such as sensitivity, specificity, speed, and cost.

FAQ

References

• D’Souza, D. H., & Joshi, S. S. (2016). Foodborne Viruses of Human Health Concern. Encyclopedia of Food and Health, 87–93. doi:10.1016/b978-0-12-384947-2.00727-3
• Petrović, T., & D’Agostino, M. (2016). Viral Contamination of Food. Antimicrobial Food Packaging, 65–79. doi:10.1016/b978-0-12-800723-5.00005-x
• Koopmans M. FOOD-BORNE VIRUSES FROM A GLOBAL PERSPECTIVE. In: Institute of Medicine (US). Improving Food Safety Through a One Health Approach: Workshop Summary. Washington (DC): National Academies Press (US); 2012. A9. Available from: https://www.ncbi.nlm.nih.gov/books/NBK114484/
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• https://www.ifst.org/resources/information-statements/foodborne-viral-infections
• https://www.news-medical.net/health/What-are-Foodborne-Viruses.aspx