Viral hepatitis

Viral hepatitis is a group of systemic infectious diseases caused by various hepatitis viruses, which mainly result in liver damage. At present, based on clearly defined etiological classification, there are five types: A, B, C, D and E. The clinical manifestations are similar, mainly fatigue, loss of appetite, oil aversion and abnormal liver function, with some patients exhibiting jaundice.

Type A and type E are mainly acute infections, which are transmitted through fecal-oral route. Type B, C and D are mostly chronic infections, with high risk of developing liver cirrhosis or hepatocellular carcinoma, which are mainly transmitted through blood and body fluids.

1. Viral hepatitis A

Viral hepatitis A, referred to as hepatitis A for short, is an acute infectious disease caused by hepatitis A virus infection. The source of infection are hepatitis A patients and individuals with asymptomatic infections. The most prevalent causes of infection are consuming contaminated food or water, as well as close contact with an infected individual.

The incubation period generally lasts 14-39 days, with an average of 28-30 days. The clinical symptoms mainly include fever, nausea, vomiting, oil aversion, diarrhea, fatigue, loss of appetite, yellow urine, yellow skin and mucous membrane.

Clinical manifestations are closely related to age. Young children usually present as having a symptomatic infection, while older children and adults generally have symptomatic infection. Hepatitis A is a vaccine-preventable disease, and vaccination with hepatitis A vaccine can effectively prevent infection. The hepatitis A vaccine in the national immunization program is live attenuated hepatitis A vaccine or inactivated hepatitis A vaccine.

2. Viral Hepatitis B

Viral hepatitis B, referred to as hepatitis B for short, is an infectious disease caused by hepatitis B virus (HBV) infection, which usually results in liver inflammation and necrosis.

Anyone who tests positive for the hepatitis B surface antigen (HBsAg) in the blood is contagious. Hepatitis B is mainly transmitted through mother-to-child, blood and sexual contact. The general population is susceptible.

Newborns infected with HBV are easy to become chronic after infection, and some adults are considered high exposure risks, such as medical staff, people with frequent blood exposure, organ transplant recipients, people who often receive blood transfusions or blood products, family members of HBsAg positive people, men who have sex with men or individuals with multiple sexual partners, and injecting drug users.

The incubation period of acute hepatitis B generally lasts 45-160 days, with an average of 120 days. In the acute stage, digestive tract symptoms such as anorexia, general fatigue, nausea, vomiting and abdominal pain are the main symptoms, which may be accompanied by jaundice. Once acute hepatitis B becomes chronic, it is easy to turn into chronic hepatitis, liver cirrhosis and liver cancer. Based on the disease progression following infection, clinical diagnoses can be categorized into a spectrum of conditions, including chronic HBV carrier, inactive HBsAg carrier, acute hepatitis B, chronic hepatitis B, cirrhosis, and liver cancer. 

Standardized antiviral treatment for chronic infected people can effectively suppress virus replication, delay disease progression and reduce the risk of liver cirrhosis and liver cancer. Hepatitis B is a vaccine-preventable disease, and vaccination against hepatitis B can effectively prevent hepatitis B. The hepatitis B vaccine in China's national immunization program is the recombinant hepatitis B vaccine.

Viral Hepatitis C

Viral Hepatitis C is an infectious disease primarily characterized by inflammatory liver lesions caused by hepatitis C virus (HCV) infection. It is mainly transmitted through three routes: blood, sexual contact, and mother-to-child transmission. Blood transmission is the predominant mode of HCV spread, and the population is generally susceptible.

HCV infection can lead to acute or chronic conditions. When viremia persists for six months without spontaneous clearance, the infection progresses to the chronic stage. The risk of chronic HCV infection in adults is as high as 60% to 80%. Many HCV patients remain in a latent infection state, with most showing no obvious symptoms or signs. Some may experience fatigue, decreased appetite, nausea, abdominal distension, and discomfort or pain in the right hypochondriac region.

As the disease progresses, it can result in long-term chronic inflammation, hepatocyte necrosis, and fibrosis in the liver. Without proactive treatment, 15-20 percent of chronic HCV patients may further develop into cirrhosis or liver cancer, posing significant health risks.

Currently, direct antiviral drugs for HCV can achieve clinical cure rates of over 95 percent and are eligible for medical insurance reimbursement. A comprehensive hepatitis C control strategy—centered on expanded testing and treatment—is crucial. This involves promoting both "test all who should be tested" and "accessible testing for all willing individuals" to maximize case identification. All anti-HCV positive cases should receive prompt nucleic acid testing (NAT) for confirmation. Those with confirmed Viremia (positive NAT) must then be linked to timely, standardized antiviral therapy to achieve a clinical cure. This systematic approach effectively prevents progression to cirrhosis and liver cancer, eliminates sources of infection, and reduces or prevents secondary transmission of HCV.

Viral Hepatitis D

Viral Hepatitis D, abbreviated as HDV, occurs only in individuals already infected with the hepatitis B virus (HBV), and dual infection can exacerbate the condition.

Viral Hepatitis E

Viral Hepatitis E, abbreviated as HEV, is an acute infectious disease caused by the hepatitis E virus. The primary sources of infection are patients and those with symptomatic infections, and the main mode of transmission is through the digestive tract.

The general population is susceptible and the incubation period is typically 15-60 days, with an average of 40 days. Major clinical symptoms include fatigue, decreased appetite, abdominal pain and tenderness, nausea, vomiting, fever, and jaundice.

In patients with chronic liver disease, there is a risk of developing severe hepatitis after infection. Individuals with immunosuppression or severe immune deficiency caused by other reasons also face the risk of progressing to chronic hepatitis E after infection. Paying attention to diet, water hygiene, and vaccination can effectively prevent hepatitis E.