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Hepatitis B

10 Million Injection Drug Users May Have Hepatitis B or C

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Approximately 10 million injection drug users (IDUs) worldwide might be infected with hepatitis C virus (HCV), and more than 1 million may be living with hepatitis B, according to a meta-analysis of data from over 70 countries published in the July 28, 2011, advance online edition of The Lancet.

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Sharing needles and other equipment for injecting drugs is an major risk factor for transmission of viral hepatitis and HIV, but detailed estimates of the extent of the problem are not available.

Paul Nelson from the National Drug and Alcohol Research Centre at the University of New South Wales in Sydney, Australia, and colleagues therefore set out to estimate national, regional, and global prevalence and population sizes for IDUs with hepatitis B and C.

The researchers performed a systematic search of peer-reviewed databases (Medline, Embase, and PsycINFO), "grey literature" (reports by government agencies, industry, etc.), conference abstracts, and online resources relating to hepatitis B virus (HBV) and hepatitis C virus (HCV) in IDUs.

Out of 4386 peer-reviewed and 1019 grey literature sources, they reviewed 1125 sources in full. The collected information about HCV antibody (anti-HCV) status, indicating infection with HCV, which typically results in chronic infection; HBV core antibody (anti-HBc) status, which indicates either past HBV infection -- which usually results in spontaneous clearance -- or vaccination; and HBV surface antigen (HBsAg) status, which indicates current infection.

They then calculated prevalence estimates and combined these with IDU population sizes (mainly derived from the Reference Group to the United Nations on HIV and Injecting Drug Use) to calculate the approximate number of IDUs who are HBV or HCV positive.

Results

Hepatitis B:

  • The researchers identified eligible reports on anti-HBc status in 43 countries and HBsAg status in 59 countries, representing 65% and 73%, respectively, of all IDUs.
  • Again, anti-HBc prevalence rates varied widely, from 4.2% in Slovenia to 85.0% in Mexico.
  • HBsAg status, or current infection, varied both across and within countries (for example, 3.5%-20.0% in the U.S. and 3.7%-30.9% in Iran.
  • Prevalence estimates suggested 5%-10% of IDUs in 21 countries and more than 10% in 10 countries are HBsAg positive.
  • Overall, 6.4 million IDUs might be anti-HBc positive (range 2.3-9.7 million) and 1.2 million (range 0.3-2.7 million) might be HBsAg positive or currently infected.
  • The largest populations were in east Asia and southeast Asia (0.3 million) -- where HBV is endemic and many were presumably infected as children -- and in eastern Europe (0.3 million).

Hepatitis C:

  • The researchers located eligible reports on anti-HCV prevalence among IDUs in 77 countries, representing 82% of all IDUs.
  • Prevalence of anti-HCV positivity varied greatly among countries, ranging from 9.8% to 97.4%.
  • Prevalence estimates suggested 60%-80% of IDUs had HCV in 25 countries and more than 80% did so in 12 countries.
  • Overall, about 10.0 million IDUs worldwide (range 6.0-15.2 million) might be anti-HCV positive.
  • The largest populations of HCV positive IDUs were in China (1.6 million; 67.0%), the U.S. (1.5 million; 73.4%), and Russia (1.3 million; 72.5%).
  • The number of IDUs thought to have HCV is about 3.5 times larger than the 2.8 million (range 0.8-6.2 million) estimated to be living with HIV.

"More IDUs have anti-HCV than HIV infection, and viral hepatitis poses a key challenge to public health," the study authors concluded.

They explained in their discussion that reported IDU population size estimates reflect the number of current or recent users of injection drugs, not people who have ever used them, so the total number of cases of hepatitis B or C attributable to injection drug use would be higher.

"Efforts to prevent, treat, and reduce harms related to liver disease in IDUs are essential -- especially in situations in which HIV has successfully been prevented or managed -- because the large numbers of IDUs infected with HCV and significant morbidity resulting from this infection mean that the health and economic costs of HCV transmitted by injecting drug use might be as high as (or higher than) those of HIV," they wrote.

"Evidence about the effect of needle and syringe programs and provision of other injection equipment on prevention of HCV infection is scarce, but reduction of risk is paramount, particularly during the period of initiation to injecting when incidence of HCV is highest," they continued. "[The] potential role of HCV treatment in the prevention of HCV transmission in IDU populations warrants further investigation," but high cost and side effect remain as barriers.

Turning to hepatitis B, Nelson and colleagues noted that "[b]ecause of the high rate of chronic HCV infection in IDUs, HBV infection is particularly likely to show HBV and HCV coinfection, which is associated with more rapid progression of liver disease and attendant mortality."

"Vaccination against HBV must be prioritized for all susceptible IDUs, especially those already infected with HCV," they wrote. "A substantial reduction in the burden of HBV infection in IDUs is expected in countries with universal infant vaccination programs, once these individuals reach the age at which acquisition of HBV through injecting drug use is most common."

"Correctional facilities provide one opportunity to vaccinate, treat, and reduce the transmission of viral hepatitis in a population with high rates of injecting drug use, HBV, and HCV, many of whom cycle in and out of the community," they suggested.

Investigator affiliations: National Drug and Alcohol Research Centre, University of New South Wales, Sydney, NSW, Australia; Victorian Infectious Diseases Reference Laboratory, North Melbourne, VIC, Australia; College of Nursing, New York University, New York, NY; Beth Israel Medical Center, New York, NY; Centre for Population Health, Burnet Institute, Melbourne, VIC, Australia; Centre for Health Policy, Programs and Economics, School of Population Health, University of Melbourne, Melbourne, VIC, Australia.

7/29/11

Reference

PK Nelson, BM Mathers, B Cowie, et al. Global epidemiology of hepatitis B and hepatitis C in people who inject drugs: results of systematic reviews. The Lancet (free full text). July 28, 2011 (Epub ahead of print).