One of the main causes of chronic hepatitis, cirrhosis, and hepatocellular cancer in the world is the hepatitis B virus (HBV) (HCC). There are 2 billion persons who, according to serology, have either had or are now infected with HBV. There are more than 350 million HBV chronic carriers. Asia and the Western Pacific are home to almost 75% of chronic carriers.
According to reports, cirrhosis, liver failure, or HCC occurs in 15–40% of HBV-infected patients, and 500, 000–1.2 million persons worldwide per year succumb to the illness. The high morbidity and mortality from HBV-related diseases contribute significantly to the burden of HB worldwide.
HBV was initially identified as the cause of “serum hepatitis,” the most prevalent kind of viral hepatitis transmitted parenterally. It is also a significant cause of both acute and chronic hepatitis. The incubation period for the hepatitis B virus ranges from one to six months. The acute infection’s clinical characteristics are similar to those of the other viral hepatitides.
About 1% of people who have fulminant hepatitis die from it. After an acute infection, there are two outcomes: either full recovery (along by lifelong immunity) or persistent illness. The latter is more prevalent in immunocompromised individuals and affects 5–10% of infected adults, 30% of infected children, and 90% of infected neonates at birth.
In other parts of the world, persistent HBV infection is far more common.
There are three levels of endemicity for the prevalence of chronic HBV infection worldwide. The endemicity of HBV infection is correlated with the age at infection.
- Extreme Endemicity
Infection with HBV is significantly more common in some places than others around the world. In developing nations with sizable populations like South East Asia, China, sub-Saharan Africa, and the Amazon Basin, where at least 8% of the population is an HBV chronic carrier, hepatitis B is highly prevalent. 70 to 95 percent of the people in these regions have serological evidence of having had HBV in the past or present. The majority of illnesses happen in children or infants. There is no evidence of acute HBV-related disease in children because the majority of infections are asymptomatic, but adult rates of chronic liver disease and liver cancer are substantial.
- Mid-Range Endemicity
In several areas of Eastern and Southern Europe, the Middle East, Japan, and South America, hepatitis B is relatively endemic. Between 10 and 60% of people show signs of infection, and 2 to 7% are lifelong carriers. HBV-related acute illness is widespread in these locations because adolescents and adults are frequently infected; nevertheless, infections in newborns and young children primarily sustain high rates of chronic infection. Infant, early childhood, and adult transmission all occur in these locations in heterogeneous ways.
- Minimal endemicity
Most industrialized regions, including North America, Northern, and Western Europe, and Australia, have low HBV endemicity. Only 0.5–2% of the population in these areas is a chronic carrier of HBV, which affects 5-7% of the population there. Most HBV infections in these regions affect teenagers and young adults who belong to reasonably well-defined high-risk categories, such as injectable drug users, homosexual men, healthcare professionals, and those who frequently need blood transfusions or hemodialysis.
Hepatitis B Symptoms, Transmission, and Diagnosis
Perinatal and horizontal transmissions are the two main ways that the hepatitis B virus spreads throughout the world. The majority of transmissions worldwide are caused by perinatal transmission, which happens during childbirth between infected mothers and their newborns.
The second mode of transmission is horizontal, and it can happen due to open wounds (cuts and scratches), blood transfusion, inadequate infection control measures to prevent blood-borne infections in healthcare facilities, sexual transmission, and risky health practices like body piercing, unsafe drug injection, body tattooing, and scarification with unsterile tools and other equipment.
The likelihood of chronic hepatitis B virus infection declines with age in susceptible persons, depending on the method of virus transmission. 90% of infections encountered during the prenatal period will develop into chronic diseases. Up to 20–60% of children under the age of five who have HBV will go on to develop chronic infection, as will 5–10% of adults and older kids.
There is sufficient data to demonstrate that intimate and sexual connections can transmit HBV. Sexually promiscuous individuals, particularly active homosexual men who frequently switch partners, have an extremely high risk of contracting the hepatitis B virus. Blood, as well as different bodily secretions like saliva, breast milk (including colostrum), and serous fluids, have all been found to contain the HBV surface antigen. These bodily secretions have been linked to the virus’s spread.
Hepatitis transmitted by touch is therefore extremely important. The virus can be accidentally spread through the use of a small amount of blood or fluids contaminated with blood during medical or surgical procedures, vaccination using equipment like needles and syringes that haven’t been properly sterilized, drug injections, tattooing, ear and nose piercings, acupuncture, razors, shared toothbrushes, towels, and other blood-tinted linens.
Other factors, including ceremonial circumcision, bloodletting, repeated bites by bloodsucking arthropod vectors, traditional tattooing, and scarification, are associated with transmission in particular climates in the tropics and war countries and should be taken into consideration. However, research on the role that biting insects play in the spread of HBV has shown mixed results. HBsAg has been found in a variety of mosquito and bed bug species that were either caught in the wild or fed on infected blood in lab experiments.
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Hepatitis B virus replication in insects has not yielded any conclusive results. Additionally, there is no epidemiological proof that flies mechanically transmit the HBV virus. Bile, urine, and feces have all been found to contain HBsAg, frequently as a result of blood contamination. It is unknown whether HBV can spread through urine and feces. Unless it is tainted with blood, urine is not contagious. There is no proof that the virus is transmitted through the air. Although clustering of HBV can occur in familial contexts, this is unrelated to genetics and does not reflect genital or maternal transmission. The methods of HBV intrafamilial transmission are still unknown.
When they are first infected, the majority of people don’t show any symptoms. However, some patients get the acute disease with symptoms that linger for several weeks. These symptoms include stomach discomfort, black urine, severe exhaustion, nausea, and vomiting. Acute liver failure, which can result in mortality, can develop in people with acute hepatitis. A portion of people who have HBV infections goes on to acquire severe liver conditions like cirrhosis and hepatocellular carcinoma, which have a high morbidity and mortality rate.
Since it is impossible to distinguish between hepatitis B and other viral hepatitis on the basis of clinical findings, laboratory confirmation of the diagnosis is crucial. Hepatitis B patients can be diagnosed and monitored using a variety of blood tests. They can be used to differentiate between acute and persistent infections. To maintain the safety of blood and prevent unintentional transmission, the WHO advises that all blood donors be screened for hepatitis B.
As of 2019, 30.4 million individuals—or 10.5% of those predicted to have hepatitis B—knew they had the disease, and 6.6 million (22% of those who had been diagnosed—were receiving treatment. The percentage of children under five who have chronic HBV infection has decreased to slightly under 1%, per the most recent WHO data.