Viral hepatitis

Viral hepatitis is when the liver becomes inflamed because of a virus. This can happen suddenly in a condition called acute hepatitis, or it can develop slowly over a long time in a chronic form. Over time, chronic hepatitis can lead to serious health problems, including liver damage and cancer.

The most common viruses that cause hepatitis are hepatitis A, B, C, D, and E. But other viruses, like cytomegalovirus, Epstein–Barr virus, yellow fever, and herpes simplex, can also cause liver inflammation in some cases. These infections can affect people of all ages and are found all around the world, making it important to understand how they spread and how to stay healthy.

Mode of transmission

Viral hepatitis can spread in two main ways. Some types, like hepatitis A and E, are spread through contaminated food or water. These usually cause a short-term illness that gets better on its own. Other types, like hepatitis B and C, spread through blood and body fluids. These can cause longer-term health problems and might be passed from a mother to her baby during birth, or through contact with infected blood during medical treatments.

There are ways to prevent or treat the most common types of hepatitis. Vaccines can prevent hepatitis A and B. Treatments for hepatitis C exist, though they can be expensive. In 2013, around 1.5 million people worldwide died from viral hepatitis, mostly from hepatitis B and C. East Asia, including Mongolia, was especially affected.

Hepatitis viruses

The most common reason for hepatitis, which is when the liver gets inflamed, is caused by viruses. Even though we call all these different viruses "hepatitis," they are not connected to each other. There are five main viruses that cause this, known as hepatitis A, B, C, D, and E.

Hepatitis viruses
	Hepatitis A virus (HAV)	Hepatitis B virus (HBV)	Hepatitis C virus (HCV)	Hepatitis D virus (HDV)	Hepatitis E virus (HEV)
Viral species	Hepatovirus A	Hepatitis B virus	Hepacivirus C	Hepatitis delta virus	Orthohepevirus A
Viral family	Picornaviridae	Hepadnaviridae	Flaviviridae	Kolmioviridae	Hepeviridae
Genome	(+)ssRNA	dsDNA-RT	(+)ssRNA	(−)ssRNA	(+)ssRNA
Antigens		HBsAg, HBeAg	Core antigen	Delta antigen
Transmission	Enteral	Parenteral	Parenteral	Parenteral	Enteral
Incubation period	20–40 days	45–160 days	15–150 days	30–60 days	15–60 days
Severity/Chronicity	Mild; acute	Occasionally severe; 5–10% chronic	Subclinical; 70% chronic	Exacerbates symptoms of HBV; chronic with HBV	Mild in normal patients; severe in pregnant women; acute
Vaccine	2 injections; at least 20 years of protection	3 injections; lifetime protection	None available	None available, but not considered necessary; Hep B vaccine provides protection	Investigational (approved in China)

Viral hepatitis types

Hepatitis A

Main article: Hepatitis A

Hepatitis A is a sickness of the liver caused by a virus. It spreads when a person eats food or drinks water that has been contaminated. This type of liver sickness does not continue for a long time. The body usually builds protection against it after getting better. Doctors tell people with Hepatitis A to rest and drink plenty of fluids. There is a vaccine that helps prevent Hepatitis A for many years. Most people get better in about two months, but some might feel sick for longer.

Hepatitis B

Main article: Hepatitis B

Hepatitis B is another type of liver sickness caused by a different virus. This one can stay for a long time in the body. It can spread through contact with blood or other body fluids. There is a vaccine that protects against Hepatitis B forever. Without treatment, Hepatitis B can cause serious health problems later in life.

Hepatitis C

Main article: Hepatitis C

Hepatitis C is a liver sickness that also lasts a long time. It usually does not show signs for many years. It can spread through blood contact. There are medicines that can help clear the virus from the body. Hepatitis C can lead to serious liver problems if not treated.

Hepatitis D

Main article: Hepatitis D

Hepatitis D can only happen if a person also has Hepatitis B. It needs Hepatitis B to live and grow. The Hepatitis B vaccine also helps prevent Hepatitis D.

Hepatitis E

Main article: Hepatitis E

Hepatitis E is like Hepatitis A but can be more serious, especially for pregnant women. It spreads through contaminated food or water and usually gets better on its own.

Hepatitis F virus

Main article: Hepatitis F

Scientists once thought there might be a virus called Hepatitis F, but they have not found strong proof that it really exists.

GB virus C

Main article: GB virus C

GB virus C is a virus that might spread through blood or close contact. It does not seem to cause liver sickness.

2022 hepatitis of unknown origin

Main article: 2022 hepatitis of unknown origin in children

In 2022, many children around the world got sick with liver problems of unknown cause. Scientists think a virus might be involved but have not found the exact cause yet.

Hepatitis A
Marker	Detection Time	Description	Significance
Faecal HAV	2–4 weeks or 28 days	–	Early detection
Ig M anti HAV	4–12 weeks	Enzyme immunoassay for antibodies	During acute Illness
Ig G anti HAV	5 weeks–persistent	Enzyme immunoassay for antibodies	Old infection or reinfection

Hepatitis C
Marker	Detection Time	Description	Significance	Note
HCV-RNA	1–3 weeks or 21 days	PCR	Demonstrates presence or absence of virus	Results may be intermittent during course of infection. Negative result is not indicative of absence.
anti-HCV	5–6 weeks	Enzyme Immunoassay for antibodies	Demonstrates past or present infection	High false positive in those with autoimmune disorders and populations with low virus prevalence.
ALT	5–6 weeks	–	Peak in ALT coincides with peak in anti-HCV	Fluctuating ALT levels is an indication of active liver disease.

Relationship between hepatitis C virus and liver cancer

The hepatitis C virus (HCV) can cause both short-term and long-term infections, which are a big reason why people develop liver cancer, known as hepatocellular carcinoma (HCC). This type of liver cancer is a main cause of death in people who have long-lasting HCV infections.

Having HCV for a long time is a major risk for liver cancer. The biggest risk happens when a person has HCV along with other infections like hepatitis B virus (HBV) or human immunodeficiency virus (HIV). Other factors that increase the risk of liver cancer in people with HCV include having other liver diseases, certain types of the virus, diabetes, obesity, and lifestyle choices like smoking or drinking alcohol. The goal of treating HCV is to remove the infection, stop it from spreading, and lower the chance of developing liver cancer.

Other viruses

The virus first known to cause liver problems was the yellow fever virus, which is spread by mosquitoes. Many other viruses can also cause problems in the liver, including:

Adenoviruses
Arenaviruses: Guanarito virus, Junín virus, Lassa fever virus, Lujo virus, Machupo virus, and Sabiá virus
Bunyaviruses: Crimean–Congo hemorrhagic fever virus, Dobrava virus, Hantaan virus, Puumala virus, Rift Valley fever virus, and Seoul virus
Coronavirus: severe acute respiratory syndrome virus
Erythrovirus: Parvovirus B19
Filoviruses: Ebola virus and Marburg virus
Flaviviruses: dengue, Kyasanur Forest disease virus, Omsk hemorrhagic fever virus, and yellow fever virus
Herpesviruses: cytomegalovirus, Epstein–Barr virus, varicella-zoster virus, human herpesvirus 6, human herpesvirus 7, and human herpesvirus 8
Orthomyxoviruses: influenza
Picornaviruses: echovirus
Reovirus: Colorado tick fever virus, reovirus 3

Some studies suggest that the virus KIs-V might also be linked to liver problems, but more research is needed.