Hepatitis B epidemiology and demographics

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Jolanta Marszalek, M.D. [2]

Overview

Chronic Hepatitis B (HBV) is a major global health problem. According to the World Health Organization (WHO), more than 2 billion people have been infected with HBV. It is a major cause of chronic liver disease worldwide, affecting an estimated 1.25 million people in the United States and more than 240 million people worldwide.

Epidemiology and Demographics

Prevalence

Worlwide, the prevalence rate of HBV ranges from <2% in developed countries to ≥8% in developing countries. Chronic HBV affects an estimated 800,000 - 1.4 million persons in the U.S.

Adapted from Center for Disease Control and Prevention(CDC)

Prevalence of HBV is greater in certain high risk groups:

• High-risk sexual activity (79% of persons with newly aquired HBV infection engage in high-risk sexual activity or IDU)
• Injection-drug use (IDU)
• Known exposures (i.e., occupational, household, travel, and healthcare-related)

16% of persons deny a specific risk factor for infection.

Adapted from Center for Disease Control and Prevention(CDC)

Incidence

In the U.S, the overall incidence rate in 2011 was 0.9 cases per 100,000 population. A total of 2,890 cases of acute HBV were reported. Between 1991 and 2010, the incidence of HBV has decreased by approximately 82%. The decrease was greatest among children largely due to implementation of routine vaccination in 1991. Since 2001, fewer than 30 cases of acute HBV have been reported annually among children born in 1991 or later, the majority of whom were international adoptees or children born outside of the U.S who were not fully vaccinated.

Although the incidence of HBV is declining in the U.S., it is important to note that reported cases underestimate the true incidence of HBV infection due to the asymptomatic nature of early infections and because of under reporting of symptomatic cases.

Worldwide, there are over 4 million cases of acute HBV every year.

Adapted from Center for Disease Control and Prevention(CDC)

Age

In many low risk regions of the world, the highest incidence of HBV is seen in teenagers and young adults. In endemic areas of Africa and Asia, most infections occur in infants and children. In 2011, the highest rates of HBV were among persons aged 30–39 years (2.00 cases/100,000 population), and the lowest were among adolescents and children aged <19 years (0.04 cases/100,000 population).

Gender

In 2011, the rate of HBV in the U.S was 1.7 times higher among males than among females (1.18 cases and 0.69 cases per 100, 000 population, respectively).

Race

The incidence of HBV infection in the U.S. differs significantly by race and ethnicity with the highest rates among blacks; rates are higher among Hispanics than non-Hispanics.

Developed Countries

Countries and regions with the highest standards of living such as North America, Western and Northern Europe, Australia, and parts of South America have the lowest prevalence of HBV infection. The carrier rate here is less than 2%, and less than 20% of the population is infected with HBV. In the U.S., chronic HBV is responsible for approximately 3,000 annual deaths from associated chronic liver disease. 47 - 70% of U.S. residents with chronic HBV were born in other countries. While the prevalence of chronic HBV infection among younger, vaccinated foreign-born U.S residents is decreasing, the rate of liver cancer deaths continues to be high among certain foreign-born U.S. populations. The rate of liver cancer deaths is highest among Asian/Pacific Islanders, reflecting the high prevalence of chronic HBV in this population.

Developing Countries

Regions with the highest prevalence of HBV include Sub-Saharan Africa, Southeast Asia, and the Pacific Basin ( excluding Japan, Australia, and New Zealand). Higher rates of chronic HBV are also found in southern parts of Eastern and Central Europe, the Amazon Basin, the Middle East, and India. In these areas, about 70 - 90% of the population becomes HBV-infected before the age of 40, and 8 - 20% of people are HBV carriers. In countries such as China, Senegal, and Thailand, infection rates are very high in infants, and continue through early childhood. In Panama, New Guinea, Solomon Islands, Greenland, and in populations such as Alaskan Indians, infection rates in infants are relatively low and increase rapidly during early childhood. The prevalence of HBV is decreasing in many regions including North Africa, the Middle East, Latin America, and Southeast Asia.