A population-based study of chronic hepatitis C in immigrants and non-immigrants in Quebec, Canada

Immigrants from intermediate and high HCV prevalence regions of Sub-Saharan Africa, Asia and Eastern Europe had a 1.5–1.7-fold higher risk of HCV compared to non-immigrants. Immigrants were older and less likely to be male compared to non-immigrants cases and were diagnosed a mean of almost 10 years after arrival. Non-immigrant cases were more likely than immigrant cases to have behavioral co-morbidities such as problematic alcohol or drug use, and to be HIV co-infected. The age and sex adjusted HCV annual notification rate decreased by almost 5% per year in non-immigrants but remained relatively unchanged in immigrants between 1998 and 2008. As a consequence, the proportion of HCV cases occurring in immigrants doubled over the study period from 5 to 11%.

In our study, immigrants from Sub-Saharan Africa, Asia and Eastern Europe had a higher HCV risk compared to non-immigrants whereas immigrants from North Africa and the Middle East and Latin America and the Caribbean had a lower risk. The pattern of the magnitude of HCV risk by region of origin in immigrants in our study reflects published epidemiology of HCV in immigrants after arrival in host countries as well as in their countries of origin [18, 24, 32]. HCV seroprevalence is a reasonable surrogate measure for the magnitude of HCV risk by region of origin and was used as there were no comparative studies on HCV notification rates in immigrants. HCV seroprevalence in Asia, Africa, and Central and Eastern Europe is intermediate to high (2 to 4%) whereas it is low (1–2%) in Canada, Western Europe, the US, Latin America and the Caribbean and most countries in North Africa except Egypt and Iraq [15, 19, 32]. Furthermore, high HCV reported rates in immigrants from Congo (151/100,000 and RR 5.6), Pakistan (123; 4.5), and Cambodia (117; 4.3) and are also consistent with global epidemiology as these countries all have a high HCV seroprevalence ranging from 2.3 to 6.7% [32].

We found major demographic and behavioral differences between immigrants and non-immigrants with HCV. The demographic and behavior characteristics of HCV in non-immigrants is consistent with the characteristics of HCV cases in Canadian surveillance data [15, 33]. HCV cases in Canada occur more frequently in males and in current and previous intravenous drug users and have a high risk of HIV co-infection [15, 33]. There is little data on HCV-infected immigrants in Canada or other high income countries. Our findings are similar to two other Canadian studies that also found that immigrants with HCV were older, and were less likely to be male or to have problematic drug use compared to non-immigrants [34, 35]. In our study there were significant differences in the HCV risk by age group for immigrants and non-immigrants. Male and female immigrants of all ages were found to have HCV, likely reflecting the fact that exposure to contaminated blood or unsafe medical procedures can occur at any age and equally by gender. In non-immigrants, cases were more likely to occur in young and middle age adults and reflects the age group at highest risk for initiation and active intravenous drug use [21]. Although the numbers are small, immigrants <15 years of age were more likely to have HCV than non-immigrants and may, in part, be due to perinatal transmission.

The decreasing trend of reported HCV cases seen in non-immigrants of 4.9% per year between 1998 and 2008 is consistent with the trends of notified HCV cases in Canada, the US and Australia over this same period [9, 33]. In contrast, rates of reported cases in immigrants during this same period remained unchanged. This could be explained by increased screening or reporting of HCV in immigrants, newly acquired infections after arrival, increased numbers of immigrants from at risk countries arriving over the study period, or a steady rate of imported HCV cases acquired in their country of origin in the setting of no routine post-arrival screening. The latter is the most likely explanation given that HCV screening in Canada during the study period was focussed on those with risk factors for HCV exposure such as intravenous drug use and did not identify immigrants as a high risk group [16, 36]. Furthermore, immigrants are at low risk for HCV transmission after arrival in Canada given the low prevalence of problematic drug use in this group and the fact that the number of new immigrants from at risk countries was stable during the study period [20]. With this dataset we cannot eliminate the possibility that immigrants may have become infected with HCV after arrival in Canada during periods of travel back to their countries of origin. Canadian immigrants are less likely to access health care due to several barriers including language, cultural difference or infrastructure [37, 38]. This coupled with the lack of a targeted HCV screening program may explain the 10-year timeframe to diagnosis after arrival. These findings, taken together, support the hypothesis that immigrants are most likely to have been infected with HCV in their countries of origin through unscreened blood products or unsafe medical procedures rather than through injecting drugs in Canada. The long asymptomatic period of chronic HCV and lower health care access may explain the long delay in diagnosis after arrival.

The major strengths of this study are that it is a large population based sample spanning almost a 10-year period in which immigration status was accurately assigned through linkage with the landed immigration database. All notified HCV cases were ascertained, were laboratory confirmed, and acute and chronic cases were identified and differentiated with standardized case definitions. This study has some limitations including the well-known underestimation of cases in a passive surveillance system such as MADO. These data are also influenced by health seeking behavior, non-nominal reporting for some groups, and increased screening of those at increased risk of hepatitis such as drug users. Due to the anonymous reporting of certain cases or due to missing demographic information or RAMQ numbers, almost 20% of cases did not link. Unlinked cases were not differentially distributed between immigrants and non-immigrants, thus calculated rates in this study are under estimated by 20% in both groups, but without misclassification between these groups. The increased reported HCV rate observed between 2002 and 2004 is likely due to the fact that HCV became reportable in Quebec in 2002 and that there was enhanced surveillance during this period of time [39]. We only have access to data up until 2008 however, we expect that the trends in case rates, underlying co-morbidities and time to diagnosis after arrival for immigrants found in our study would be similar to that after 2008. This is because there are no targeted HCV screening programs for immigrants in Quebec or Canada and this was the case both before and 2008. The accuracy of diagnostic codes to detect co-morbidities in RAMQ databases has not been validated, however good accuracy has been shown in other administrative databases [29]. Administrative coding for problematic drug use is limited by the fact that it is not possible to determine if drug use was intravenous or by another route and cases of prior drug use (in those not actively using drugs), may not be detected. We used the same codes for problematic drug use as were used in a recently published study [28]. Despite these limitations our data show important trends in HCV in immigrants compared to non-immigrants that are both plausible and are externally validated.

Untreated HCV is an enormous health and economic burden in Canada and other low HCV prevalence countries. This burden is projected to increase over the next decade unless the large pool of asymptomatic infected individuals are detected and treated prior to developing end stage liver disease [40, 41]. Eradication of HCV is now within reach given the recent availability of highly effective, well tolerated, short course, direct acting anti-viral treatments [12]. Identifying all asymptomatic HCV-infected individuals and successfully linking them to care is a critical issue that will need to be addressed in order to decrease the rising economic and individual burden from HCV.