Viral hepatitis

Viral hepatitis is when a virus makes the liver swollen and irritated. This can happen quickly, called acute hepatitis, or it can develop slowly over a long time, called chronic hepatitis. If it lasts a long time, it can sometimes cause health problems later on.

The most common viruses that cause hepatitis are hepatitis A, B, C, D, and E. Other viruses, like cytomegalovirus, Epstein–Barr virus, yellow fever, and herpes simplex, can also make the liver irritated in some cases. These infections can happen to anyone, at any age, and they are found all over the world. That is why it is important to learn how they spread and how to keep 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.

Other types, like hepatitis B and C, spread through blood and body fluids. These can cause longer-term health problems.

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.

East Asia, including Mongolia, was especially affected.

Hepatitis viruses

The most common reason for hepatitis, when the liver gets inflamed, is caused by viruses. Even though we call all these viruses "hepatitis," they are not related to each other. There are five main viruses that cause this, called 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 someone eats food or drinks water that is not clean. This sickness does not last very long. The body usually stays safe from it after getting better. Doctors tell people with Hepatitis A to rest and drink fluids. There is a vaccine that helps prevent Hepatitis A for many years. Most people feel better in about two months, but some might feel sick longer.

Hepatitis B

Main article: Hepatitis B

Hepatitis B is another type of liver sickness caused by a different virus. This one can stay in the body for a long time. 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 health problems later in life.

Hepatitis C

Main article: Hepatitis C

Hepatitis C is a liver sickness that can last 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 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 infections that last a long time. These infections can lead to liver cancer, called hepatocellular carcinoma (HCC). HCC can be a serious cause of death in people with long-term HCV infections.

Having HCV for many years increases the risk of liver cancer. The risk is even higher if a person also has hepatitis B virus (HBV) or human immunodeficiency virus (HIV). Other factors that can raise the risk include having other liver diseases, certain types of the virus, diabetes, obesity, and lifestyle choices like smoking or drinking alcohol. Treating HCV aims to remove the infection, stop it from spreading, and reduce the chance of liver cancer.

Other viruses

The first virus known to cause problems in the liver was the yellow fever virus, which spreads through mosquitoes. Many other viruses can also affect 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.