Diversity and Detection of Foodborne Viruses

Diversity and Detection of Foodborne Viruses

Introduction

In present, it is been identified that viruses are the main causes contributing to foodborne disease. Minimally processed food such as bivalve Molluscs and fresh produce are one category. Enteric viruses are the main contributors to foodborne disease comprises of Rotavirus, Adenovirus Sapo virus, Hepatitis A and E viruses. Foodborne disease is transmitted by dirty food, though can also be transmitted through human contact and environmental contamination, for instance, water. Further, it is been recognized that foodborne disease outbreak has a relation to the readymade, ready to eat food if prepared by an infected person. In many countries, the severity of risk by foodborne viruses has been identified but diagnostic tools for these viruses are still not easily available.  There are different ways this virus can pass to humans but the main foodborne viruses are the ones that are infected through the gastrointestinal tract. Noroviruses are the most common foodborne virus, followed by Hepatitis that is a big health threat. The risk management tools can support the government of different countries to manage or reduce the effect of the viruses to certify consumer health from foodborne disease. In the review, we are going to discuss the different foodborne viruses, how these increase health burden, how it can be managed, or mitigated, in end, a conclusion relevant to it will be a draw.

Discussion

For better health and wellbeing ensuring food safety is important, but in recent years, food-borne disease burden has affected many part of the world, contaminated food comprising bacteria, viruses, and parasites has been recognized as threat, therefore many countries has provided guidelines to food industries to work as per decided legislation to control the outbreak of these diseases (Havelaar et al., 2016). Yet, the major cause of illness is related to food-borne disease, which indicates that burden estimation is still not correct. Increasing population influence the environment setting, for instance, excessive sewage discharge that make finding clean waters for production a difficult task. These type mixture of animal and human pathogens emphasize the probability of animal pathogens in food and that will be difficult to control. Effective hygiene standards can help in effective control of the disease but flaws in food process might increase the risk of contamination. Therefore, in consideration to food safety and people health perspective we need to analyse the different factors that can help in better understand of the food-borne disease.

What are common Food-borne Viruses

Small microorganisms ranging from 0.02 to 0.4 in micrometres in diameter are few characteristics of viruses, while bacteria are 0.5 to 5 micrometres in size (Tack et al., 2019). Also, their structural biological properties’ are very different. Viruses utilise host cells to duplicate, and diverse (for example, DNA or RNA), however bacteria are free living. The virus structure is interconnected to the environmental resistance of the virus, if more multifaceted structure particles being less unaffected. Viruses can cause disease in humans, plants and animals. Single virus can causes a specific type of illness as each viruses has their own host range. The transmission process of these viruses is also different, for instance, it can be transmitted when infected person coughs or through respiratory route, or orally, when infected person prepare food and it is eaten by unaffected individuals, it also get transmitted though by sexual intercourse, contact with contaminated blood, or infected animals or mosquitoes (Liu, 2018).

Most frequently involved viruses in foodborne infections are HAV and Nov, but viruses like Rotavirus, hepatitis E, SapoVirus, coronaviruses and Adenvirus can also be transmitted through food. These viruses are shed in human faeces and can infect the humans through oral route, these virus are usually small particles with single RNA genome and are without envelope except Rotavirus (Double RNA). Coronavirus contain an envelope and Adenoviruses and Paroviruses are DNA viruses (Dodd, Aldsworth & Stein, 2017). It is known, that these viruses persistent in environment settings and can resist process to control contamination in foods. Occasionally these viruses can be transmitted through food but their usual way of contamination/transmission is different, pathogenic influenza and severe acute respiratory syndrome causing coronavirus.

Characteristics of foodborne disease:

• It is identified that Virus need host/living cells to able to replicate. We know that bacteria is living cells and cannot replicate in food. Therefore, viruses not change food properties due to contagion.
• Few infectious particle ranging from 1 to 100 can cause illness. 
• Infected person stool has high level of viral particles.
• Viruses can be transmitted through oral route
• Many food-borne viruses did not have an envelope that’s the reason they are very stable outside the host and has resistance to radiation, drying, etc.
• Zoonotic virus’s transmission through food is common for bacterial pathogens. 

NoV (NoroVirus)

In Norovirus person to person virus transmission is very common and it’s very infectious. After human contact food contamination is most common factor for this virus spread, and results outbreaks. NoV infection can cause disease to people of all ages, the symptoms are initially mild but with time it became severe, elderly people can be majorly affected by this disease, especially if have any underlying condition. Social gathering places are reported to be the risky area for virus outbreak, but by many health professionals considered as healthcare infections rather than infection caused by food (Mitake et al., 2016). NoV foodborne spread is detected and related with wide range of food items, such as food prepared by infected person, bivalve molluscs’ contamination, spread through contaminated food (e.g. berries) burden of NoV disease is high and in recent cause USA $3 billion, many life has been lost due to this virus, and because of this NoV is named as one of the costly pathogens causing foodborne disease (Xia et al., 2016).  The foodborne viruses has created new challenges for risk managers as it vital for them to identify the epidemiology, infectivity, persistence between this viruses to control the risk of virus more effectively. Thus, a vital consideration for risk assessment and management is needed comprising the hygiene guidelines to prevent the infection where possible.

Hepatitis A

 There are many developing countries where risk of Hepatitis A infection is high and majority of people are effected in their childhood, in childhood infection is asymptomatic, and almost all adults are immune to the disease.  With time risk of HAV infection has reduced due to improve living standards.  But childhood HAV infection later in life have severe disease outcome.  Globally there are 1.4 million cases annually that indicated that we still need more awareness to tackle the infection. HAV is transmitted through contaminated food or water or person-to person contact. The ready to eat food if not effectively prepared can carry risk of the virus. Countries with low vaccine availability, poor food standards are still at risk of epidemic from the virus.

HumanRotavirus (HRV)

Human Rotavirus are main cause of viral gastroenteritis in children across the globe that cause severe dehydrating illness (example diarrhoea). In many countries human rotavirus is been main cause of high children mortality rate (Jiang, Glass, Wang & Gentsch, 2020) as a result of severe dehydration caused by viral toxin. Common cause of Human Rotavirus spread is person-to-person contact, but areas which has poor hygiene foodborne and waterborne contamination is been main reason for spreading of the disease. 

Hepatitis E virus (HEV)

Hepatitis E virus is referred as an endemic disease, particularly in area which has low hygiene standards, resulting serious hepatitis. It is recognized that illness is very severe in pregnant women causing risk of increase mortality rate.  HEV is main cause of viral hepatitis in developing countries, and the transmission of the disease is due to contaminated water that cause the outbreak. Hepatitis E is also known as travel disease as infection in people are increasing across the country. Lately, hepatitis E is discovered in pigs that infected many humans who have no history of foreign travel.  Also the transmission can take place by consuming uncooked/raw meat, however it is unclear how significant it is in mode of transmission.

Coronavirus

In 2020, the outbreak of coronavirus has shocked the world, originated from china now the virus is causing pandemic across the globe. It is highly contagious and need extreme protection to prevent spread of the virus, however, key characteristics of the virus is still in process of discovery, but the symptoms of the disease are both symptomatic and asymptomatic. The process of transmission involves person-to-person contact, area touch by infected person also became infected, food handle by infected person, etc. world is still suffering from the disease and specific measure to prevent the disease outbreak is still unclear.

Despite having many mode for transmission, transmission through food and water is common for all viruses, thus, we can say that more strict hygiene standards are needed especially in areas of poor hygiene to control the outbreak of the foodborne disease. 

What are detection method

Usually the conventional methods for detecting the foodborne pathogens in food depend on microorganism maintenance on agar plates and biochemical identification, this method is simple and low-cost but time consuming and limited low sensitivity may increase risk of transmission if it failed in identifying pathogens. In recent, advanced methods with high sensitivity have been made for detection of foodborne pathogens and overcome the conventional method limitations, however, it is been identified by researcher that we still need more effective rapid method to avoid the risk of transmission of foodborne disease(Li, Butot, Zuber & Uyttendaele, 2018).  Methods like RT-PCR, NGS (next generation sequencing), microarray, etc. have made the detection of virus like norovirus, and HAV possible. 

Nucleic-acid method: nucleic acid-based method can help in detecting toxin-related genes in the pathogens, and specific genes in certain pathogens, this method help in avoiding ambiguity and result error, recently, the defined nucleic acid—based method are PCR ( polymerase chain reaction).

PCR: PCR detection of viral nucleic acid is beneficial method for sensitive detection of foodborne viruses in food. It operates be intensifying target DNS sequence in three steps, at high temperature two single Stranded DNA is change into single stranded DNA. Then, specific primers will strengthen to the DNA strands followed by procedure called polymerization where primers are stretched in presence of thermostable DNA polymerase and deoxyribonucleotides.

Multiplex PCR: multiplex PCR is extremely helpful as it permits the synchronous recognition of a few pathogenic microbes by acquainting various preliminaries with enhance DNA districts coding for explicit qualities of each targeted bacterial strain.

Microarray:  these are made up of glass slide coated with specific oligonucleotide probes these are chemically created short sequences (25-80 bp).  Each probe target a gene sequence. The viablein situ-synthesized arrays are high-density microarrays that are short oligonucleotide probes synthesized unswervingly on the surface of the microarray these are also helpful in detection of foodborne pathogens, however costly compare to other method.

How it is transmitted

The important factor that affect foodborne transmission is virus stability outside the host, though foodborne viruses show different resistance in different settings such as heat, cold, acid, radiation, etc. but generally they are very tough and can easily survive in the environment that increase the risk of illness in the populace. Along the food chain the risk for possible contamination is high, for instance, high transmission for Nov and HAV though infected food handlers. Some category of animal viruses also causes illness in humans, people consuming raw/uncooked meat are at high risk of suffering from these viruses. It is possible that animal viruses enter the food chain through animal products (for example, meat) consume by humans, later cause spread of the virus through human. Animal viruses with foodborne transmission include HPAI, Hepatitis E, coronavirus, H5N1. Etc. (Khare, Tonk & Rawat, 2018).  As describe below there are three main contamination of foods.

First: sewage and faeces

It is recognized that viruses spread can be possible through untreated sewage, though common methods of sewage treatment may not be adequate to eliminate the viruses but it can reduce the risk at certain extent. Common route for bivalve contamination is through direct contact with sewage (Wu et al., 2018), fresh produce items through use contaminated waters in irrigation or as fertilizer also increases the risk of virus spread.  Also sewage related contamination can cause food to become highly contagious with serval viruses. This results in human becoming infected with more than one virus strain and presence of these strains replicates host cell that provide environment to develop new virus. There are two ways this can occur, first through process called recombination that is big issue in terms of food safety, and second is re-assortment that involves progeny of two viruses infecting single cell causing new viruses to develop (Chen et al., 2017). All these mechanisms contribute to diversity of viruses and their combinations.

Through infected food handlers:

Spread of enteric virus through stool is common and person can start shedding viruses after 12-14 hours after exposure, for instance, norovirus, coronavirus, etc.  And continue till several weeks depending on virus type, and treatment. Because of immediate shredding of virus after exposure it is possible that infected individual may shed the virus even before experiencing any symptoms, which increased the risk of virus spread. In present, covid-19 start the higher level of asymptomatic shedding (Patrick et al., 2018).  If food handlers are shedding viruses and they are not using protective equipment it is possible that the food they handle may become highly contaminated with that virus, and that food can easily will spread to others who come in contact with that food.   Contamination of food can take place at any stage of food chain, for instance, food items produced during the harvest, distribution or at homes, if it comes in contact with contagious person the food will be contaminated. 

Spread of viruses can also take place through vomiting. For instance, as we know that norovirus infection lead to vomiting, several results show outbreak of the virus through vomiting (Ribot & Hise, 2016).  The development of aerosol in space where infected person has vomited can cause widespread contamination in the environment. Viruses persistence in contaminated environment also define mode of transmission.

Viruses contaminated food products look, taste, and smell normal and because of this characteristic it is not easy to detect the contagious food (Velebit et al., 2019).  Though, most waterborne or foodborne viruses has resistant to disinfection chemicals, heat and high ph. Therefore, even low level of virus contamination might survive in the food at the point of the consumption, and many viruses low dose of infectious particles is sufficient to cause severe illness.

Why Foodborne viruses persistent

Foodborne virus’s stability during processing:

Enteric Viruses are intractable and unaffected to many food processing and preservation procedure, for instance, foodborne viruses can survive for long time even at high pH values, though difference are observe depended on type of virus but even a low infectious virus particle can survive many disinfections chemical and heat (Nasheri, Vester & petronella, 2019). It is been identified that HRV and HAV are more resistant toward this processes, also, difference of virus survival also depends on different processing conditions. For instance, pasteurize milk inactive hepatitis A virus however very extensive processing is obligatory to attain effective inactivation (Maunula & Von Bonsdorff, 2016). As enteric viruses has resistant to ionizing radiation, even freezing has little effect on survival of virus.  Due to virus persistence in food processing controlling spread of virus is tough task, thus, require effective management strategies that focus on hygiene, prevention of the contamination rather than cure.

Stability of viruses in environment:

The stability of some foodborne viruses in environment affecting the risk of morbidity and mortality. For instance, human rotavirus via vomiting found to be survive in the environment up to 9 days at 20 degree Celsius (Bosch & Pinto, 2016).   Viruses might persist up to 2 months by surviving on domestic environment such as paper, tile, etc. viruses like Adenoviruses and polystyrene can survive up to 35 days on plastic and in low humidity environment (Bosch et al., 2018). HRV and HAV can survive in low humidity, on other hands, Enteroviruses can survive in high humidity. This survivability indicated the diverse nature of virus and threat to populace due to their stability in environment. This relationship also indicated the necessity of specific virus related data so that more effective plan and precautions can be taken to avoid the spread of these viruses. Lastly, in contaminated water it is possible that viruses can survive for long period, for instance, Rotavirus can survive in mineral water (Bosch & Pinto, 2016). Thus, survival of viruses depends on virus characteristics that is biggest challenges for health department to gather specific data.

Nevertheless, it is important to note that virus’s high resistance to food processing and environmental is not sole reason of foodborne disease transmission, virus’s ability to infect gastrointestinal tract is also a potential foodborne transmission factor.

What is the process of decontamination?

Hand sanitation: decontamination of hands is vital to reduce the chances of virus spread, though no agent is absolutely affected in eliminating the virus from the skin but hand sanitization can help people to reduce the risk of contacting foodborne viruses (by 1 to 2 log 10 drop I virus titre) (Fusco et al., 2017). Using hand sanitizer with proper hand wash is more effective in sanitization of hands than using sanitizer only as some infective virus may remain on hands that can still be dangerous for the health.

Surface sanitization:  Virus’s persistence to environment is important factor to consider for foodborne virus epidemics. As mentioned above that viruses survivability factors also depend on virus types, therefore exact data related to their survivability is unclear, however is recognized to be depend on temperature and moisture most commonly (Nasheri et al., 2020). As infected person can contaminate the setting the washing and disinfection of surfaces is vital for virus spread control during food preparation. Though, just like hand disinfection, the effectiveness of eliminating virus from surface completely through sanitization is not clear. Most surface sanitisers lack effectiveness against enteric viruses. Difficulties in establishing the impact of control measures on the infectivity of foodborne viruses

Food matrices:  detection of foodborne viruses through food matrices is also used to identify the foodborne diseases.  Detection of bivalve molluscan are established and known in many countries to control the outbreak. Though process for virus detection is diverse, but strong standards to prevent the contamination in agriculture practise by using tool like GAP and monitoring help in controlling the outbreak of these viruses.  The national guidelines for application of PCR for identification of microorganisms in food samples can also help prevention of virus spread (Torok et al., 2018). As we studied above, that foodborne viruses vary from each other and have diverse process of survival that creates biggest challenges for government, and health department to come up with specific virus related data that can support in better methodology to tackle foodborne diseases. Considering present coronavirus outbreak we can say that even with limited data related to nature of the virus we can say sanitization is only key to reduce the spread of the diseases, however specific way to treat the virus is unknown due to its stability in environment, but considering prevention is better than cure, working in compliance to food processing guidelines, hygiene standards, and other prevention measure can support in controlling the spread of the viruses outbreak.

Conclusion

Food-borne disease burden has affected many part of the world, as the contaminated food comprising bacteria, viruses, and parasites has been recognized as threat to health. Foodborne viruses are diverse in terms of their stability to survive the food processing procedure and in different environment condition. May foodborne viruses are intractable and unaffected to many food processing and preservation procedure, for instance, foodborne viruses can survive for long time even at high pH values, though difference are observe depended on type of virus but even a low infectious virus particle can survive many disinfections chemical and heat. The different virus survivability on temperature also vary from each other which is biggest challenges in gathering specific data to control these viruses. Also there many mode of transmission of the foodborne disease, thus, considering the diverse characteristics of viruses we can say that prevention is key to control the disease using vital tool for monitoring the food processing chain and sanitizing it to control the spread of foodborne diseases.

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