More U.S. Immigrants May Have Hepatitis B than Previously Estimated

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The number of foreign-born individuals with chronic hepatitis B virus (HBV) infection in the U.S. may be considerably higher than earlier estimates suggest, according to a study described in the November 22, 2011, advance online edition of Hepatology.

Although the U.S. and many other countries now routinely vaccinate infants and adolescents against HBV, people infected years or decades ago continue to carry the virus, which can lead to advanced liver disease including cirrhosis and hepatocellular carcinoma.

Hepatitis B is highly prevalent in regions such as Asia and Africa, where it is considered "endemic." In the absence of vaccination or preventive therapy, HBV is frequently transmitted from mother-to-child and a large proportion of people in these areas are infected as babies or young children.

In the U.S., immigrant communities -- especially Asian and Pacific Islander communities -- have high hepatitis B prevalence compared with the general population. However, the precise number of people with the disease is unknown because HBV screening is often not part of routine care and surveillance programs are not well established or adequately funded.

In this analysis, Kris Kowdley from Virginia Mason Medical Center and colleagues sought to estimate the number of foreign-born people with chronic hepatitis B living in the U.S., according to their country of origin.

The study authors performed a systematic review of reports about hepatitis B surface antigen (HBsAg) seroprevalence rates in 102 countries, identified in the PubMed database from 1980 through July 2010.

Data from 1373 articles meeting the inclusion criteria were extracted into country-specific databases; surveys that included individuals with lower or higher HBV risk than the general population (for example, injection drug users or prisoners) were excluded. Data were combined in a meta-analysis to determine country-specific pooled hepatitis B prevalence rates. These rates were then multiplied by the number of foreign-born people from each country living in the U.S. in 2009, according to the U.S. Census Bureau.

Results

"This analysis suggests that the number of foreign-born persons living with chronic hepatitis B in the U.S. may be significantly greater than previously reported," the investigators concluded. "Assuming 300,000-600,000 U.S.-born persons with chronic hepatitis B, the total prevalence of chronic hepatitis B in the U.S. may be as high as 2.2 million."

Prior published estimates of the total number of people with chronic hepatitis B in the U.S. have ranged from 550,000 to 2 million, of whom 40% to 70% are thought to be foreign-born, the authors elaborated in their discussion. About 2.8% of refugees entering the U.S. during 2006-2008 who were tested through screening programs were HBsAg positive, compared with only 0.1% to 0.2% of people born in the U.S.

The Institute of Medicine concluded that estimates of chronic hepatitis B prevalence based on National Health and Nutrition Examination Surveys (NHANES) were low because people at greatest risk for HBV in the U.S. -- including homeless people, individuals living in prisons and other institutions, and foreign-born people -- are under-represented.

Because hepatitis B prevalence is so much higher among immigrants than U.S.-born people, this study offers an alternative approach to calculating the total burden of chronic hepatitis B by determining the number of foreign-born people from census data and estimating their rates of chronic hepatitis B using published studies.

"Better estimates of the true burden of chronic hepatitis B and the ethnic and cultural characteristics of the affected population will help develop programs for prevention, earlier diagnosis, and linkage to care," the researchers concluded.

Investigator affiliations: Center for Liver Disease, Digestive Disease Institute, Virginia Mason Medical Center, Seattle, WA; Plan A, Inc., Mountain View, CA; Centers for Disease Control and Prevention, Epidemiology and Surveillance Branch, Division of Viral Hepatitis, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Atlanta, GA; UCSF School of Medicine and UC Berkeley Joint Medical Program, Berkeley, CA.

12/6/11

Reference

KV Kowdley, CC Wang, S Welch, et al. Prevalenceof chronic hepatitis B among foreign-born persons living in the United States by country of origin. Hepatology. November 22, 2011 (Epub ahead of print).