Epidemiology of Hepatitis B Disease

 Viral hepatitis is a term commonly used for several clinically similar yet etiologically and epidemiologically distinct diseases

Hepatitis B virus (HBV) infection is a global public health problem. The World Health Organization estimated that, in 2015, there were 257 million HBV carriers in the world and roughly 887,000 died that year from HBV-related liver disease.

Hepatitis B virus (HBV) infection is considered a serious public health problem worldwide, especially in less developed countries. It is estimated that 70% of new chronic HBV infections occur in low-income countries.

Hepatitis B virus (HBV) infection results in substantial human morbidity and mortality, predominantly through the consequences of chronic infection. Recent estimates of the number of people chronically infected with HBV have ranged from 240 million to 350 million.

It is estimated that approximately two billion people worldwide have evidence of past or present infection with hepatitis B virus (HBV), and 257 million individuals are chronic carriers (ie, positive for hepatitis B surface antigen [HBsAg])

The overall prevalence of HBsAg is reported to be 3.5 percent; however, it varies depending upon the geographic area.

As an example, the prevalence of chronic HBV in adults ranges from 0.4 to 1.6 percent in regions of America, 1.2 to 2.6 percent in Europe, 1.5 to 4.0 percent in Southeast Asia, 2.6 to 4.3 percent in the Eastern Mediterranean, 5.1 to 7.6 percent in the Western Pacific, and 4.6 to 8.5 percent in the African regions

The lower prevalence in children less than five years old reflects the effectiveness of the global vaccination program against viral hepatitis B; however, there is a need for higher vaccination coverage, in particular birth-dose HBV vaccine, to completely eliminate HBV infection among children.

The wide range in the prevalence of chronic HBV infection in different parts of the world is largely related to differences in the age at infection, which is inversely related to the risk of chronicity. The rate of progression from acute to chronic HBV infection is approximately 90 percent for prenatally acquired infection

HBV was estimated to have resulted in 786,000 deaths, the vast majority being attributable to liver cancer (341,000 deaths) and cirrhosis (312,000 deaths.

However, the burden of HBV infection is geographically disparate, dependent on the differing modes of transmission predominant in the population and the resulting age at infection, which determines the probability of progression to infection. In addition, the epidemiology of HBV infection globally is changing because of the impact of universal infant vaccination programs and through migration between high- and low-prevalence populations.

In countries where chronic HBV infection affects more than 8% of the population, the majority of these individuals were infected at birth or in early childhood, when the risk of progression to chronicity is high. High-HBV prevalence is common in much of the Asia Pacific and sub-Saharan African regions of the world. Globally, it has been estimated that 45% of the world's population lives in an area of high prevalence. There is evidence to suggest that vertical transmission is more common in Asia than in Africa, where a greater proportion of women are highly infectious at childbearing age, relating in part to predominant HBV genotypes that influence the likelihood of HBeAg positivity and high levels of HBV DNA during peak childbearing ages.