FRIDAY, June 1, 2012 (MedPage Today) — More than 1.3 million foreign-born residents of the U.S. are living with hepatitis B (HBV), according to a new estimate.
The prevalence of chronic hepatitis B infection among the foreign-born — about 3.45 percent — is 10 times higher than among native-born residents, according to Kris Kowdley, MD, of the Virginia Mason Medical Center in Seattle, and colleagues.
The numbers are at least double those in a 2006 estimate by the CDC and would bring the total prevalence of hepatitis B in the U.S. to about 2.2 million people, Kowdley and colleagues reported online in Hepatology.
About 40 percent of foreign-born people living with HBV — or just under 515,000 — come from just three countries, they found: China, Vietnam, and the Philippines, where endemic HBV rates are high.
"Our analysis suggests the total prevalence of chronic HBV is significantly higher (than previous estimates), exceeding 2 million cases or twice the number previously reported," Kowdley said in a statement.
The value of the study lies in providing "convincing data that numerous and diverse foreign-born populations in the United States are at risk for chronic hepatitis B," commented John Ward, MD, and Kathy Byrd, MD, both of the CDC.
In an accompanying comment article, Ward and Bryd argued that the findings could help public health officials pick out people at risk and direct prevention efforts more effectively.
Previous estimates have been limited, Kowdley and colleagues noted, because many at-risk groups, including the foreign-born, tend to be under-represented in national health surveys.
"There is a wide discrepancy in the current estimates of the chronic HBV burden in the U.S.," Kowdley said.
To help overcome those limitations, his group reviewed medical literature from around the world for national HBV seroprevalence rates from 1980 to 2010, excluding groups with higher or lower risks of chronic HBV than the general population.
All told, they identified 256 seroprevalence surveys in emigrants to the U.S. from 52 countries and 1,797 surveys in the general populations of 98 countries.
The researchers used those data to develop country-specific background rates of chronic HBV for the 102 countries of origin for immigrants to the U.S. as determined in the U.S. Census 2009 American Community Survey.
The background rates were multiplied by census data on the number of people from each country now living in the U.S., in order to get an estimate of the prevalence in each immigrant community.
The analysis suggested that 1.32 million foreign-born people have chronic HBV, with a 95 percent confidence interval from 1,54 million to 1.61 million.
About 58 percent of the chronically infected immigrants came from Asia and 11 percent from Africa — where the disease is "hyper-endemic" — but 7 percent came from Central America, where rates are lower but many more people move to the U.S.
Assuming that between 300,000 and 600,000 U.S.-born people have chronic HBV, Kowdley and colleagues noted, the total national prevalence would be some 2.2 million.
The authors cautioned that data on chronic HBV were limited for many countries — one-third had conducted only a handful of surveys — and often varied markedly from one survey to another within a nation.
Also, much of the data was collected before 2000, they noted.