Hepatitis A virus

What is Hepatitis A Virus?

Hepatitis A Virus (HAV) is a highly contagious liver infection caused by the Hepatitis A virus. It’s one of several different types of hepatitis viruses that affect the liver’s ability to function properly. Unlike other forms of hepatitis, HAV infection is usually short-term and does not lead to chronic liver disease. However, it can cause severe symptoms and be dangerous in certain populations such as older adults or those with pre-existing liver conditions.

The virus is primarily spread when an individual ingests food or water contaminated with the fecal matter of an infected person. This can occur when an infected person prepares food without washing their hands thoroughly, especially after using the restroom.

Structure and Classification

HAV is a picornavirus, a type of RNA virus. Its structure comprises a protein shell (capsid) encasing the RNA genome. The capsid is icosahedral and lacks an envelope, which contributes to the virus’s resistance to environmental factors like temperature and humidity, making it a formidable challenge in food safety.


Transmission of Hepatitis A is predominantly through the fecal-oral route, either from person-to-person or through ingestion of contaminated food or water. This transmission mode underscores the crucial importance of proper hygiene and sanitation practices in food handling and preparation to prevent Hepatitis A outbreaks.

What Foods Can Be Contaminated?

Hepatitis A virus (HAV) has a robust nature that allows it to survive in a variety of food products. While any food can become contaminated if handled improperly, certain types of food are more commonly associated with HAV.

Shellfish and Seafood

Shellfish, particularly oysters, clams, and mussels, are frequently identified as vehicles for HAV transmission. They have a tendency to concentrate the virus because they filter large volumes of water while feeding, which may be contaminated with sewage containing HAV.

Fresh Produce

Fruits, vegetables, and other fresh produce can also be significant sources of HAV if they are grown, harvested, or processed under unsanitary conditions. For instance, produce irrigated with contaminated water or handled by infected workers can become a vehicle for HAV transmission.

Ready-to-eat Foods

Ready-to-eat foods are those that are consumed without further cooking or food preparation. If handled by an infected person, these foods can easily become contaminated with HAV as they bypass any heat treatment that might otherwise inactivate the virus.

Frozen Berries

There have been several outbreaks associated with frozen berries contaminated with HAV. The freezing process does not kill the virus, and contamination can occur at any point from farm to table.

Undercooked Foods

Undercooking food can also lead to HAV transmission. Foods that are not cooked to the proper temperature may not kill the virus, leaving it viable and capable of causing infection.

The potential for foodborne transmission of Hepatitis A emphasizes the importance of adhering to good hygiene practices and ensuring that food products are sourced from reputable suppliers following the appropriate safety standards.

How Does It Affect Human Health?

Hepatitis A virus (HAV) infection can range from a mild illness lasting a few weeks to a severe illness lasting several months. Unlike other types of viral hepatitis, HAV does not cause chronic liver disease, but it can cause significant symptoms and lead to serious health complications in certain populations.


The common symptoms associated with HAV infection include:

  • Jaundice (yellowing of the skin and eyes)
  • Fatigue
  • Abdominal pain, particularly on the right side below the rib cage (location of the liver)
  • Loss of appetite
  • Nausea and vomiting
  • Fever
  • Dark urine
  • Clay-colored stools

These symptoms usually appear 2 to 6 weeks after exposure and may last a few weeks to several months.

At-Risk Populations

Certain populations are at higher risk for severe disease if infected with HAV:

  • Older adults: The severity of illness increases with age, with older adults more likely to experience severe symptoms or require hospitalization.
  • Individuals with pre-existing liver disease: Those with other liver conditions like Hepatitis B or C, or cirrhosis are at higher risk for severe illness if infected with HAV.

Long-term Implications

While HAV infection doesn’t lead to chronic liver disease, it can cause acute liver failure, a condition in which the liver loses its functioning rapidly. However, this is extremely rare and occurs more commonly in individuals with pre-existing liver diseases or older adults.

The health impact of Hepatitis A reinforces the importance of food safety measures to prevent the transmission of this virus through the food supply, as well as the need for HAV vaccination among at-risk populations.

How Common is Illness?

Hepatitis A infection was once fairly common but the incidence has significantly declined in many parts of the world due to the advent and widespread use of effective vaccines. However, the prevalence of Hepatitis A still remains a concern in certain areas and among certain populations.

Global Prevalence

The global burden of Hepatitis A varies widely by region. In developed countries with good sanitary and hygienic conditions, the incidence of HAV infection is lower, while in developing regions or those with poor sanitation, the virus is more prevalent. The World Health Organization (WHO) categorizes regions into high, intermediate, and low endemicity based on the level of HAV seroprevalence.


Outbreaks of Hepatitis A can still occur, even in developed countries. These outbreaks are often traced back to contaminated food or water sources. For example, certain outbreaks have been associated with imported frozen berries or shellfish from areas with high HAV endemicity.

Vaccination Impact

Vaccination against Hepatitis A has had a significant impact on reducing the incidence of the disease. Many countries have introduced Hepatitis A vaccination in their national immunization schedules, which has contributed to a decline in the number of cases.

The varying prevalence of Hepatitis A underscores the importance of continued vigilance in food safety practices, especially in food and water sourcing, to prevent outbreaks and reduce the burden of HAV infection.

Where Does It Come From?

Understanding the origins and common sources of Hepatitis A virus (HAV) is crucial for implementing effective food safety measures. The virus is primarily human-borne, with infections resulting from ingestion of contaminated food or water or from direct person-to-person contact.

Human Carriers

Infected individuals are the main reservoirs of HAV. They can shed the virus in their feces for several weeks, with the highest level of contagiousness occurring two weeks before symptoms appear. This asymptomatic shedding is a significant challenge for controlling the spread of the virus.

Environmental Sources

Contaminated water sources are a common environmental reservoir for HAV. The virus can survive in water for extended periods, making waterborne transmission a significant concern. Foods that come into contact with contaminated water at any point from cultivation to consumption can become vehicles for HAV transmission.

Contaminated Food

Food products can become contaminated with HAV at any point along the food supply chain—from the farm where they are grown, to the table where they are served. The handling of food by infected individuals, particularly if they do not practice good personal hygiene, is a common source of foodborne HAV outbreaks.

Travel and Endemic Regions

Travelers to regions with high or intermediate endemicity of HAV may become infected and introduce the virus into areas with lower endemicity. Imported foods from such regions also pose a risk of HAV introduction.

Understanding the common sources and transmission pathways of HAV aids in the development and implementation of effective food safety measures to prevent and control outbreaks, protecting public health.

How is it Affected by Environmental Factors?

The stability and persistence of Hepatitis A Virus (HAV) in various environmental conditions contribute to its potential for causing foodborne outbreaks. Here’s how different environmental factors affect HAV:


HAV is known for its remarkable resistance to thermal conditions. It can withstand freezing temperatures and has a moderate resistance to heat, which means that it can survive in a wide range of food processing and preparation conditions. However, cooking at high temperatures (above 85°C for 1 minute) has been shown to inactivate the virus.

pH Levels

HAV can survive in a broad pH range, typically between pH 3 and pH 7, which covers the pH of many foods. Its ability to withstand acidic conditions means it can persist in acidic foods like fruits and juices.


Although data on the exact impact of humidity on HAV is limited, the virus’s non-enveloped structure may contribute to its survival in varying humidity levels. Non-enveloped viruses like HAV are generally more resistant to environmental stresses compared to enveloped viruses.

Water Activity

HAV can survive for extended periods in fresh and saltwater, making waterborne transmission a significant concern. Shellfish harvested from contaminated waters and fresh produce irrigated with contaminated water are common sources of foodborne HAV outbreaks.

Food Matrices

The survival of HAV can also be influenced by the food matrix. For example, the virus might persist longer in certain food matrices like shellfish or berries compared to others.

Understanding the impact of environmental factors on HAV is essential for developing effective food safety measures to control its spread and prevent foodborne illness.

How Can It Be Controlled?

Controlling Hepatitis A Virus (HAV) requires a multifaceted approach that encompasses personal hygiene, sanitation, vaccination, and adherence to food safety guidelines. Here are the key strategies to control the spread of HAV, particularly in the food industry:

Personal Hygiene

  • Handwashing: Regular and thorough handwashing with soap and water is a critical step to prevent the spread of HAV, especially among food handlers.
  • Use of Gloves: Food handlers should use gloves while handling ready-to-eat foods, although this is not a substitute for proper handwashing.


  • Immunization: Vaccination against Hepatitis A is highly effective and is a primary tool for controlling HAV infection, especially among high-risk populations and food handlers.

Food Safety Practices

  • Sourcing: Source food products from reputable suppliers who adhere to good agricultural and manufacturing practices.
  • Cooking: Cook foods to the proper temperature to inactivate HAV. For instance, cooking shellfish to an internal temperature of 90°C for 90 seconds can significantly reduce the risk of HAV transmission.
  • Cleaning and Sanitation: Regular cleaning and sanitation of food preparation areas, equipment, and utensils to prevent cross-contamination.

Surveillance and Outbreak Response

  • Monitoring: Continuous monitoring and quick response to any suspected outbreaks of Hepatitis A is crucial to prevent the spread of the disease.
  • Education and Training: Educate food handlers and the public on the risks associated with Hepatitis A and the importance of food safety measures.

Regulatory Measures

  • Inspections: Regular inspections of food establishments to ensure compliance with food safety standards and guidelines.
  • Recalls and Advisories: Issuing timely recalls of contaminated food products and providing public advisories to prevent exposure to HAV.

Through a combination of these measures, the risks associated with HAV in the food industry can be significantly mitigated, contributing to a safer food supply and improved public health.

Are There Rules and Regulations?

Governments and international health organizations have established various rules and regulations aimed at preventing and controlling the spread of Hepatitis A Virus (HAV), particularly within the food industry.

International Guidelines

  • World Health Organization (WHO) and Food and Agriculture Organization (FAO): These organizations provide guidelines and recommendations for controlling foodborne viruses like HAV. They emphasize the importance of good hygiene practices in food service and production settings.

National Regulations

  • Vaccination Programs: Many countries have implemented vaccination programs targeting high-risk groups or the population at large to reduce the incidence of HAV infection.
  • Food Safety Standards: National food safety authorities establish standards and guidelines for food handling, preparation, and processing to minimize the risk of HAV contamination.

Food Industry Compliance

  • HACCP (Hazard Analysis and Critical Control Points): Food establishments are encouraged or required to implement HACCP systems to identify and control food safety hazards, including HAV.
  • Certification and Training: Food handlers may be required to undergo training on food safety and hygiene practices to ensure compliance with national and local food safety regulations.

Inspection and Enforcement

  • Regular Inspections: Food safety authorities conduct regular inspections of food service and processing establishments to ensure compliance with food safety standards.
  • Outbreak Investigations: In the event of a Hepatitis A outbreak, authorities will conduct investigations to identify the source of the contamination and take necessary actions to prevent further spread.

Import and Export Controls

  • Screening and Testing: Imported foods may be screened or tested for HAV, especially if sourced from regions with high HAV endemicity.
  • Recalls and Alerts: Regulatory authorities issue recalls and alerts for food products found to be contaminated with HAV to prevent public exposure.

Adherence to these rules and regulations, along with the development and implementation of effective food safety management systems, is crucial for controlling the spread of HAV and ensuring a safe food supply.

Resources and Further Readings

Hepatitis A Virus (HAV) – FDA – Provides information about Hepatitis A virus, its symptoms, at-risk groups, prevention, and foods linked to U.S. outbreaks of Hepatitis A.

Hepatitis A: A Food Safety Concern – Penn State Extension – Discusses the concerns surrounding Hepatitis A in the context of food safety and its implications.

Hepatitis: A PDF from Food Marketing Institute (FMI) – provides practical guidance for food retail.

Hepatitis A Prevention and Management Guidelines – CDC – Provides guidelines and recommendations on the prevention and management of Hepatitis A​.

Hepatitis A – World Health Organization (WHO) – Provides a comprehensive overview and key facts about Hepatitis A, including its impact on global health.