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GENOTYPE D AMONG INJECTION DRUG USERS (IDU) WITH ACUTE HEPATITIS B (HBV) INFECTION: AN EMERGING PATTERN?

C Osiowy¹, C Panessa², WD Hill², E Giles¹, A Andonov¹, G Butt², M Krajden²
¹National Microbiology Laboratory, Winnipeg, Manitoba; ²BC Centre for Disease Control, Vancouver, British Columbia

Hepatitis B virus (HBV) is a global problem, with an estimated 350 million chronic cases worldwide. Despite a safe and effective vaccine, a significant number of infections are acquired in adulthood due to high-risk behaviours such as IDU or sexual exposure. The eight genotypes of HBV (A to H) exhibit a distinct geographic distribution, with most North Americans infected with genotype A. The purpose of this study was to determine the risk factors and genotypes of acute HBV infections reported in the province of British Columbia from 2001 to 2005.
Cases of acute HBV in the province of British Columbia were identified from laboratory reports using a standardized case definition as part of the Enhanced Hepatitis Strain Surveillance System (EHSSS), a joint initiative between the Public Health Agency of Canada and the BC Centre for Disease Control (BCCDC). Informed consent was obtained by public health nurses and detailed interviews for risk factors and hepatitis history were conducted for each case. Sequence-based genotyping was performed by the National Microbiology Laboratory in Winnipeg.
Between 2001-2005, a total of 305 cases of acute HBV were reported to the EHSSS. Of these, 238 cases were assigned to the BCCDC for follow-up. A total of 135 samples were genotyped and risk factor information was obtained for 70 cases. Genotype distribution for the 70 interviewed cases was as follows: A (19%), B (4%), C (12%) D (63%) E (1%) and 1% unable to be genotyped. IDU was reported as a risk factor in 21/70 (30%) cases, with 12/21 (57%) reporting IDU within the previous six months. Incarceration in a correctional facility was reported in 15/70 (21%) cases, and 16/70 (23%) cases reported sexual contact with a known HBV carrier. A significant association was observed between Genotype D and IDU (chi-squared=9.8019, df=1, p<0.001) and previous incarceration (chi-squared=7.5948, df =1, p<0.005).
Genotypes of acute HBV can be used to identify emerging epidemiological transmission patterns. Genotype D was strongly associated with IDU and previous incarceration. Genotype A and foreign-associated genotypes were represented in acute HBV infections, but accounted for a small proportion of cases. Tracking genotypic patterns of acute HBV infection can help guide targeted immunization programs to high-risk populations.

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