Viral Hepatitis

The hepatitis viruses and their transmission mechanisms

• Hepatitis A virus (HAV): It is a single-stranded RNA virus belonging to the Picornaviridae family. It is mainly transmitted via the faecal-oral route, that is, through the ingestion of food or water contaminated with the faeces of infected individuals. Illness caused by HAV is generally acute and self-limiting, so most people recover fully without developing chronic hepatitis. Outbreaks are usually associated with poor sanitation conditions and contaminated raw foods, such as shellfish. Prevention of HAV is based primarily on vaccination and proper hand hygiene.

• Hepatitis B virus (HBV): It is a double-stranded DNA virus of the Hepadnaviridae family. Transmission occurs mainly through blood and other bodily fluids, including sexual transmission and mother-to-child transmission during childbirth. Unlike HAV, HBV can cause chronic infection (especially in children), which increases the risk of serious complications such as cirrhosis and hepatocellular carcinoma (liver cancer). There is an effective vaccine against HBV that provides active immunisation against the virus. It is administered in three doses during the first year of life. In addition, treatment options exist for chronic HBV infection; however, these are not curative and not all individuals with chronic infection are eligible for them.
• Hepatitis C virus (HCV): It is a single-stranded RNA virus of the Flaviviridae family. It is transmitted mainly through contact with infected blood, with the most common route being sharing needles or medical practices performed without proper sterilisation (for example, unscreened transfusions). Some individuals spontaneously clear the virus, but most develop chronic hepatitis, which may slowly progress to cirrhosis and liver cancer. Curative treatment options exist for HCV infection, enabling viral eradication in more than 95% of cases.
• Hepatitis D virus (HDV): It requires the presence of HBV in order to replicate, as it depends on its envelope. Both infections may occur either simultaneously (coinfection) or in a person already infected with HBV (superinfection). The presence of HDV worsens liver disease, increasing the risk of fulminant hepatitis, cirrhosis and long-term complications. As with hepatitis B and C, HDV is mainly transmitted through exposure to blood or other bodily fluids.
• Hepatitis E virus (HEV): It is a single-stranded RNA virus of the Hepeviridae family. It is transmitted via the faecal-oral route and is associated with the consumption of contaminated water or food. It is usually an acute and self-limiting infection, but it can be severe in vulnerable populations, especially pregnant women during the third trimester. Most HEV cases currently occur in humanitarian settings such as refugee camps.

Symptoms

The clinical presentation of viral hepatitis is variable and depends both on the type of virus and the host’s characteristics. In many cases, infection may be asymptomatic or present with non-specific symptoms such as fatigue, general malaise, nausea or abdominal pain. When liver inflammation is more pronounced, jaundice (yellowing of the skin), choluria (dark urine) and acholia (pale stools) may occur. All viral subtypes can cause acute hepatitis, but only some—HBV, HCV and HDV—can lead to chronic infections, which may progress over years to liver cirrhosis or hepatocellular carcinoma. In these cases, chronic infection can progress silently for years without obvious symptoms.

Diagnosis

The diagnosis of viral hepatitis is based on serological tests that detect markers of infection or viral exposure. When necessary, results are confirmed using molecular biology techniques that identify and quantify viral genetic material. This is an essential step in confirming active infection. Once the disease is diagnosed, additional clinical tests are carried out to assess disease severity in terms of liver inflammation, fibrosis, cirrhosis and/or liver cancer, as well as extrahepatic complications.

Diagnosis of HBV and HCV can be performed using rapid tests requiring a small blood sample. In the case of HBV, they can identify active infection through detection of the surface antigen (HBsAg), although they cannot determine whether the infection is acute or chronic. In the case of HCV, detection of anti-HCV antibodies via rapid tests indicates current or past infection, so further testing is required to confirm active infection. For HCV, molecular platforms are available for confirmatory testing at the “point of care”, meaning the individual does not need to return for an additional blood test.

Prevention

Improving access to safe drinking water and adequate sanitation systems is essential to prevent transmission of hepatitis A and E. In the case of blood-borne hepatitis, key measures include the use of sterile equipment in healthcare procedures, blood donation screening and the promotion of safe sexual practices. To prevent mother-to-child transmission of HBV and HCV, screening is carried out during pregnancy. When indicated, treatment is also provided to pregnant women with active infection in order to reduce the risk of transmission to the newborn.

In the case of hepatitis A and B, vaccines are a fundamental control tool. Hepatitis E also has an available vaccine, but its use is not yet globally widespread. There is no available vaccine for hepatitis C, but modern antiviral treatments can cure infection in more than 95% of cases. Prevention of hepatitis D is based on vaccination against HBV, as immunity to HBV prevents HDV replication.

Treatment

The therapeutic approach to viral hepatitis varies depending on the causative agent and the stage of the disease. Acute hepatitis mainly requires supportive clinical care, whereas hepatitis that may progress to chronic forms requires specific antiviral treatment.

Current treatments for hepatitis C virus are direct-acting antivirals (DAAs), which achieve very high cure rates. For hepatitis B, currently available drugs control viral replication and reduce the risk of long-term complications. Access to diagnosis and treatment remains one of the main challenges: despite global progress in prevention, deaths continue to rise because too few people are diagnosed and treated.