EPIDEMIOLOGY OF HEPATITIS C INFECTION IN ONTARIO, 2010

Transcription

1 EPIDEMIOLOGY OF HEPATITIS C INFECTION IN ONTARIO, 2010 Robert R. Remis MD, MPH, FRCPC, Juan Liu MSc Ontario HIIV Epidemiologic Monitoring Unit, University of Toronto prepared for AIDS Bureau, Ontario Ministry of Health and Long-Term Care December 2011

2 TABLE OF CONTENTS 1 INTRODUCTION METHODS Reported cases of hepatitis C, Ontario Source of data Data analysis Acute and chronic hepatitis C, EHSSS Source of data Data analysis Ontario HCV model RESULTS Reported cases of hepatitis C, Ontario Acute and chronic hepatitis C, EHSSS Ontario HCV model DISCUSSION.. 15 REFERENCES 17 LIST OF TABLES AND FIGURES

3 LIST OF TABLES AND FIGURES Section One Table 1.1 Number and rate (per 100,000 population) of reported cases of hepatitis C, Ontario, Table 1.2 Reported cases and rates of hepatitis C by year and sex, Ontario, 2005 to 2010 Table 1.3a Table 1.3b Table 1.3c Table 1.3d Table 1.3e Table 1.3f Table 1.4a Table 1.4b Table 1.4c Table 1.4d Table 1.4e Table 1.4f Number and proportion of reported cases and rate of hepatitis C by age and sex, Ontario, 2005 Number and proportion of reported cases and rate of hepatitis C by age and sex, Ontario, 2006 Number and proportion of reported cases and rate of hepatitis C by age and sex, Ontario, 2007 Number and proportion of reported cases and rate of hepatitis C by age and sex, Ontario, 2008 Number and proportion of reported cases and rate of hepatitis C by age and sex, Ontario, 2009 Number and proportion of reported cases and rate of hepatitis C by age and sex, Ontario, 2010 Number and proportion of reported cases and rate of hepatitis C by public health unit and sex, Ontario, 2005 Number and proportion of reported cases and rate of hepatitis C by public health unit and sex, Ontario, 2006 Number and proportion of reported cases and rate of hepatitis C by public health unit and sex, Ontario, 2007 Number and proportion of reported cases and rate of hepatitis C by public health unit and sex, Ontario, 2008 Number and proportion of reported cases and rate of hepatitis C by public health unit and sex, Ontario, 2009 Number and proportion of reported cases and rate of hepatitis C by public health unit and sex, Ontario,

4 Table 1.5 Table 1.6 Number and proportion of reported hepatitis C case by year, risk factor and sex, Ontario Number and proportion of reported hepatitis C case by year, risk factor and health region, Ontario Figure 1.1 Number and rate of reported cases of hepatitis C, Ontario, 1992 to 2010 Figure 1.2 Proportion of reported HCV cases by age, Ontario, 2005 to 2010 Figure 1.3 Rate (per 100,000 population) of reported HCV cases by age, Ontario, 2005 to 2010 Figure 1.4 Proportion of reported HCV cases by health region, Ontario, 2005 to 2010 Figure 1.5 Rate (per 100,000 population) of reported HCV cases by health region, Ontario, 2005 to 2010 Section Two Table 2.1 Table 2.2a Table 2.2b Table 2.2c Table 2.3 Table 2.4a Table 2.4b Table 2.4c Number and rate (per 100,000 population) of reported HCV cases by site, year of diagnosis, stage of HCV and sex, EHSSS, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by age group, stage of HCV and sex, Ottawa, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by age group, stage of HCV and sex, Hamilton, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by age group, stage of HCV and sex, London, Ontario, 2007 to 2010 Annual rate (per 100,000 population) of reported HCV cases by age group, site, and sex, EHSSS, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by risk factor, stage of HCV and sex, Ottawa, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by risk factor, stage of HCV and sex, Hamilton, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by risk factor, stage of HCV and sex, London, Ontario, 2007 to

5 Table 2.5a Table 2.5b Table 2.5c Table 2.6a Table 2.6b Table 2.6c Cumulative number and proportion of reported HCV cases by region of birth, stage of HCV and sex, Ottawa, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by region of birth, stage of HCV and sex, Hamilton, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by region of birth, stage of HCV and sex, London, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by race/ethnicity, stage of HCV and sex, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by race/ethnicity, stage of HCV and sex, Ontario, 2007 to 2010 Cumulative number and proportion of reported HCV cases by race/ethnicity, stage of HCV and sex, Ontario, 2007 to 2010 Section Three Table 3.1a Table 3.1b Table 3.2 Table 3.3 Modeled HCV prevalence (number and rate) by place of birth, sex and exposure category, Ontario, 2007 Modeled HCV prevalence (number and rate) by place of birth and exposure category, Ontario, 2007 Modeled HCV incidence (number and rate) by place of birth, sex and exposure category, Ontario, 2007 Modeled HCV prevalence by public health unit and health region, both sexes, Ontario, 2007 Table 3.4 Modeled incidence of HCV sequelae, by five-year interval, Ontario, 1967 to 2027 Table 3.5 Modeled prevalence of HCV sequelae, by five-year interval, Ontario, 1967 to

6 1. INTRODUCTION Hepatitis C virus (HCV) was first identified in 1989 <1> and is transmitted primarily through parenteral exposure (i.e. blood-borne). Sexual transmission almost certainly occurs but its public health importance is not well quantified. HCV-infected persons can remain asymptomatic for many years following initial infection. HCV is a major cause of acute hepatitis and chronic liver disease, including cirrhosis, liver cancer and decompensated liver failure. Hepatitis C is largely preventable. It is not spread through casual contact and the risk of sexual transmission is low compared to HIV and hepatitis B. In most West industrialized countries, injection drug use is the predominant risk factor for HCV acquisition, due to sharing needles, syringes and other injection equipment. Prior to the implementation of routine HCV screening of plasma and blood donors in 1990, contaminated clotting factors and blood transfusion accounted for 15-20% of HCV infections. The current risk of HCV transmission via blood transfusion is estimated to be less than 1 per 500,000 units <2>. Other potential risk factors include: sharing of other drug-related equipment (e.g. crack pipes, straws, cookers, spoons, etc.), sharing of personal hygiene items with an HCV-infected person (e.g. razors, scissors, nail clippers, toothbrush), tattooing or body piercing with contaminated equipment, and medical or dental practices involving the use of contaminated equipment. Sexual (e.g. unprotected sex with an infected partner that includes contact with blood or exchange of blood) and mother-to-child transmission can also occur but are uncommon. The HCV serologic test was first licensed in However, diagnostic testing on a broad scale did not occur until the mid-1990s when HCV infection became reportable disease in most Canadian provinces. As of 1998, in all Canadian provinces, reporting hepatitis C diagnoses to local public health units was mandatory. In 2003, under contract with Hepatitis C Program, Health Canada, Remis carried out a modeling study to model HCV incidence, prevalence and sequelae to 2002 in Canada <3>. In 2006, under a mandate from the Ontario Hepatitis Secretariat, Ontario Ministry of Health and Long-Term Care (OMHLTC), the research team refined the modeling methods and adapted them to evaluate HCV epidemiology in Ontario. As of December of 2004, they estimated that approximately 110,000 persons in Ontario were infected with HCV. 53% were injection drug users, 13% had been infected through blood transfusion and 34% by other modes of transmission <4>. The Ontario model was later updated to 2007 <5>. The present report presents the modeled HCV incidence and prevalence to 2007, reported HCV cases to the Ontario reportable disease surveillance system from 2007 to 2010, and HCV cases diagnosed from 2007 to 2010 evaluated by the Enhanced Hepatitis Strain Surveillance System (EHSSS) operated by the Public Health Agency of Canada (PHAC). 6

7 2. METHODS 2.1 Reported hepatitis C cases, Ontario Source of data Hepatitis C has been reportable in Ontario since October The current case definition requires confirmation of a positive anti-hcv antibody result using two enzyme-linked immunoassay (EIA) laboratory tests. If the antibody result is confirmed positive, the case is forwarded to local public health units for investigation and follow-up in accordance with the Ontario Public Health Standards, 2008 <6>. Case definitions in Canada, including Ontario, do not distinguish between acute and chronic HCV infections. Duplicates are removed at data entry when the identifying information of a new matches perfectly or almost perfectly a case previously entered. Case data is collected by the 36 public health units in Ontario and transmitted regularly to the OMHLTC. Obvious duplicates are identified and removed at the provincial level <4>. The Public Health Division, MOHLTC extracted data on reported hepatitis C cases from the integrated Public Health Information System (iphis) database and provided us with custom tables on the number of reported hepatitis C cases by age, sex and year and by public health unit, sex and year from 2005 to Risk factor data were incompletely collected after Given the lack of clear scientific evidence for transmission efficiency for some potential risk factors, it was difficult to develop a hierarchy mutually exclusive algorithm for risk factors and the classification of exposure category may not be fully validated for some cases Data analysis For each year from 2007 to 2010, we prepared two tables: 1) number, proportion and incidence rate per 100,000 of hepatitis C by age group and sex, and 2) number, proportion and incidence rate per 100,000 of hepatitis C by public health unit/health region and sex. We also present the number and proportion of reported hepatitis C case by year, exposure category and sex from 2007 to To calculate annual incidence, we used populations by year, sex, age group and public health unit obtained from Statistics Canada. 7

8 2.2 Acute and chronic hepatitis C cases, EHSSS Source of data To obtain a more accurate assessment of hepatitis B and C infection in Canada, the EHSSS was initiated in 1998 in four health regions in Canada, including Ottawa. Since 2006, Hamilton and London, Ontario have joined the system and contribute data on newly identified acute and chronic hepatitis B and hepatitis C infections, as well as risk factors associated with these infections. The methodology of EHSSS, case definition and classification of exposure category have been described in detail in reports published by the investigators <7, 8>. Briefly, an acute HCV infection is defined as: seroconversion from negative HCV antibody (ant-hcv) to positive anti- HCV in 12 months, and/or evidence of clinical hepatitis C requiring the satisfaction of both clinical and laboratory criteria. Clinical criteria include an acute illness with a discrete onset of symptoms. Laboratory criteria include laboratory confirmation of HCV infection and elevated serum aminotransferase levels, excluding other causes of acute hepatitis. A case which does not meet the above definition for a confirmed acute case but has laboratory evidence of HCV infection (e.g. confirmed anti-hcv positive) is classified as a chronic HCV case. A case confirmed as infected but which could not be determined to be acute or chronic is referred to as indeterminate <7, 8>. Risk factor information at six months before the onset of the infection for acute cases and lifetime risk factor information for chronic cases are collected from persons who consent and are interviewed. Cases who reported more than one risk factor for infection during the exposure period are assigned to a risk group based on a mutually exclusive hierarchy which has been previously described <7, 8>. The EHSSS provided us data on newly diagnosed acute and chronic hepatitis C infections reported in Ottawa from 1998 to 2010 and in Hamilton and London from 2006 to For the purpose of this report, we present data from 2007 to 2010 for all three sites Data analysis For each site in Ontario participating from 2007 to 2010, we prepared four tables: 1) cumulative number and proportion of reported HCV cases by age group, stage of HCV and sex, 2) cumulative number and proportion of reported HCV cases by risk factor, stage of HCV and sex, 3) cumulative number and proportion of reported HCV cases by region of birth, stage of HCV and sex, and 4) cumulative number and proportion of reported HCV cases by race/ethnicity, stage of HCV and sex. In this report, we present the annual rate of reported HCV cases using 2007 to 2010 population estimates for each site as the denominator. We also present the annual rate or reported HCV cases by age group using 2006 census population by age for each site as the denominator. 8

9 2.3 Ontario HCV model Remis derived estimates of HCV infection and its sequelae in Ontario using an actuarial model originally developed for the Canada as a whole in 2003 as noted above <3>. Estimates of prevalence-related counts were calculated as of December 2007 and incident events were calculated for the calendar year A detailed description of the methodology used in the Canadian study is summarized in Appendix A of the previous report <4>. The adaptation of the method to Ontario involved determining the characteristics of the Ontario population from census and immigration data, obtaining updated information on the epidemiology of hepatitis C in Ontario and updating the information on the progression of hepatitis C infection through its clinical stages, including complications (cirrhosis, decompensated liver failure and hepatocellular carcinoma), liver transplant and hepatitis C-related mortality. The detailed methodology used to derive the estimates in Ontario was described in the previous report <4>. 3. RESULTS 3.1 Reported hepatitis C cases, Ontario Table 1.1 presents the number and rate (per 100,000 population) of hepatitis C cases reported in Ontario from 1992 to Overall, 97,392 cases have been reported over this 19-year period. The annual number of reported cases increased after HCV reporting began and peaked in 1996, with 7,782 cases. A decreasing trend has been observed since then. About 4,500 new cases have been reported annually in the most recent six years from 2005 to The rate of reported HCV cases increased from 16.3 per 100,000 population in 1992 to a peak of 70.2 in 1996, then gradually decreased and has remained stable at about per 100,000 population from 2005 to Figure 1.1 shows graphically the annual number and rate of reported HCV cases in Ontario from 1992 to Table 1.2 presents the number and rate of reported HCV cases by sex from 2005 to Overall, 26,812 cases were reported during this six-year period. 62% of the reported cases were male. There was no obvious trend during this period, overall or by sex. The annual incidence rate was almost twice as high in males (40-48 per 100,000) as in females (23-29 per 100,000). Table 1.3a to Table 1.3f present the annual number, proportion and rate of reported HCV cases by age group and sex from 2005 to In all years and in both sexes, the majority of reported HCV cases were among persons years of age and the highest rate of HCV was among persons years of age. Figures 1.2 and 1.3 show the proportion and rate, respectively, of HCV cases by age group for both sexes together. The proportion of reported HCV cases among persons aged 15-24, 25-34, 9

10 and years significantly increased and the proportion of reported HCV cases among persons aged years significantly decreased over the six-year period. An increase in the annual rate was observed among persons years of age, from 14.6 per 100,000 population in 2005 to about 20 per 100,000 in and persons years of age from 30.5 per 100,000 in to 46.6 per 100,000 in The annual rate decreased among persons aged and years from 2005 to Table 1.43a to Table 1.4f present the number, proportion and rate of hepatitis C cases by public health unit/health region and sex for each year from 2005 to The greatest number of cases was reported from the Toronto and Central East, other health regions. Generally, the rate of HCV cases among males was higher than among females regardless of public health unit and year of report. The overall annual rate varied by public health unit, from the highest in Kingston-Frontenac-Lennox-Addington (about per 100,000) and Thunder Bay (about per 100,000), intermediate in Algoma and Haliburton-Kawartha-Pine Ridge (about per 100,000), to the lowest in the Huron and Perth public health units (less than 20 per 100,000). Figures 1.4 and 1.5 show the proportion and rate of HCV cases by health region from 2005 to Toronto case counts appeared to be decreasing whereas Southwest and Central West health regions appeared to increase in the proportion of reported HCV cases from 2005 to The annual rate of HCV cases in Southwest region increased from 28.2 per 100,000 population in 2005 to 41.5 per 100,000 in 2010, while the annual rate of HCV cases in Toronto and Eastern, other regions appeared to be decreasing. Table 1.5 presents the number and proportion of reported HCV cases by exposure category and sex from 2007 to 2009 (data on risk factors were available only for this period). The information on risk factors was not available for a significant proportion of cases: 48% of cases in 2007 and 38% in both 2008 and 2009 had no data on risk factors. From the available data on risk factors, the majority of HCV cases were injection drug users and 11-14% were persons who received blood transfusion or clotting factors in Canada prior to the implement of routine HCV screening of plasma and blood donors in 1990 or had unknown date of blood transfusion or received blood transfusion outside Canada. Persons infected by other routes of transmission accounted for about 22-30%. Table 1.6 presents the number and proportion of reported HCV cases by exposure category and health region from 2007 to Except for Ottawa, one-third to half of cases in the each health region had no data on risk factors. From the available data on risk factors, 80% of reported HCV cases in the Northern region were IDU. In contrast, about 40% of cases in the Central East, other region and 50% of cases in Toronto were IDU. IDUs comprised 60-70% of cases in the other health regions. 10

11 3.2 Acute and chronic hepatitis C cases, EHSSS Table 2.1 presents the number and annual rate (per 100,000 population) of reported hepatitis C cases by site, year of diagnosis, stage of HCV infection and sex from 2007 to The cumulative number of HCV infections for the four years was 1,031 cases in Ottawa, 715 in Hamilton, and 419 in London. For acute HCV cases, the numbers were: 119 in Ottawa, 32 in Hamilton, and 57 in London. Annual rates of HCV infection were generally slightly higher in Hamilton than in Ottawa and London. However, they were relatively stable over the four years in the three sites, with cases per 100,000 person-year in Ottawa, in Hamilton, and in London. Rates in males were higher than in women with an M:F ratio of 1.4 to 2.2. Tables 2.2a, 2.2b and 2.2c present the cumulative number and proportion of reported HCV cases by age group, stage of HCV and sex from 2007 to 2010 for Ottawa, Hamilton and London, respectively. In Ottawa, the majority (79.1%) of reported HCV cases were in persons aged 25 to 59 years, 83.2% in males and 72.4% in females. In both sexes, acute HCV cases were significantly younger than chronic HCV cases (all p<0.0001). Overall, 75.6% of acute HCV cases were in persons aged years, compared to 24.2% of chronic HCV cases which were in this same age group. In Hamilton, the majority (85.4%) of reported HCV cases were in persons aged 25 to 59 years, 87.9% in males and 80.8% in females. In contrast to Ottawa, the acute HCV cases were not as clearly younger than chronic cases. Overall, 50.0% of acute HCV cases were in persons aged years, compared to 31.4% of chronic HCV cases in this same age group. In London, the majority (83.0%) of reported HCV cases were in persons aged 25 to 59 years, with 85.8% in males and 78.5% in females. In both sexes, acute HCV cases were significantly younger than chronic HCV cases (all p<0.01). Overall, 71.9% of acute HCV cases were persons aged years, compared to 33.7% of chronic HCV cases in this same age group. Table 2.3 presents the annual rate per 100,000 population of reported HCV cases by age group, site and sex. Regardless of gender and site, the annual rate was higher in the 45-49, and year age groups. The annual rate was higher in males than in females for most age groups. For males, the highest annual rate of reported HCV cases was among persons aged years in Hamilton, with cases per 100,000 population. For females, the highest annual rate of reported HCV cases was among persons aged years in London, with 47.5 cases per 100,000 population. 11

12 Tables 2.4a, 2.4b and 2.4c present the cumulative number and proportion of reported HCV cases by risk factor, stage of HCV and sex from 2007 to 2010 for Ottawa, Hamilton and London, respectively. In Ottawa (Table 2.4a), risk factor information was available for 81.5% of the 119 acute HCV cases and 63.3% of the 872 chronic cases. Among the acute HCV cases with risk factor information, 78.4% of infections were associated with injection drug use (IDU) and 9.3% with sexual contact. Of the chronic HCV cases with risk factor information, in males, IDU accounted for 58.0% of infections, 15.7% for health care associated procedures (including blood transfusion, receipt of blood products, hemodialysis, surgery, and dental surgery), 8.7% drug snorting, 5.3% sexual contact, 3.9% other percutaneous exposures (including tattooing, body piercing, and acupuncture), and 8.4% other (including occupational exposure to blood, household contact with hepatitis C carriers, incarceration without other risk factors). In females, IDU accounted for 30.4%, health care associated procedures 23.2%, other percutaneous exposures 19.1%, drug snorting 11.3%, sexual contact 1.0%, and other 14.9%. In Hamilton (Table 2.4b), risk factor information was available for 50.0% of the 32 acute HCV cases and 29.4% of the 676 chronic HCV cases. The distribution of risk factors among the cases with risk factor information may not reflect the true distribution in Hamilton. In London (Table 2.4c), risk factor information was available for 77.2% of the 57 acute HCV cases and 99.3% of the 401 chronic cases. Of the acute HCV cases with risk factor information, 79.5% of infections was associated with injection drug use (IDU) and 9.1% drug snorting. Of the chronic HCV cases with known risk factor information, in males, IDU accounted for 71.3% of infections, drug snorting 8.9%, health care associated procedures 8.1%, other percutaneous exposures 5.3%, sexual contact 4.0%, and other 2.4%. In females, IDU accounted for 52.7%, health care associated procedures 16.0%, other percutaneous exposures 14.0%, drug snorting 8.7%, sexual contact 0.7%, and other 8.0%. Tables 2.5a, 2.5b and 2.5c present the cumulative number and proportion of reported HCV cases by region of birth, stage of HCV and sex from 2007 to 2010 for Ottawa, Hamilton and London, respectively. From the data obtained from EHSSS, region of birth information in Ottawa (Table 2.5a) was available for 82.4% of the 119 acute HCV cases and 62.4% of the 872 chronic cases. Of the acute HCV cases with known region of birth, 91.8% of infections were born in Canada. Of the chronic HCV cases with known region of birth, in males, 73.9% of infections were born in Canada, 8.5% in Asia, 7.1% in Europe and 6.8% in Africa. In females, 59.5% of infections were born in Canada, 13.7% in Africa, 12.1% in Europe, and 11.1% in Asia. In Hamilton (Table 2.5b), region of birth was available for 59.4% of the 32 acute HCV cases and 26.9% of the 676 chronic HCV cases. The distribution of region of birth among cases with 12

13 known place of birth may not reflect the true distribution in Hamilton. However, the majority of cases were born in Canada. Region of birth information in London (Table 2.5c) was available for 77.2% of the 57 acute HCV cases and 95.5% of the 401 chronic cases. Of the acute HCV cases with known region of birth, 97.7% of infections were born in Canada. Of the chronic HCV cases with known region of birth, 88.5% of infections were born in Canada, 3.9% in Europe, and 3.4% in Asia. Tables 2.6a, 2.6b and 2.6c present the cumulative number and proportion of reported HCV cases by race/ethnicity, stage of HCV and sex from 2007 to 2010 for Ottawa, Hamilton and London, respectively. In the data from EHSSS (Table 2.6a), race/ethnicity information in Ottawa was available for 82.4% of the 119 acute HCV cases and 62.8% of the 872 chronic cases. Of the acute HCV cases with known race/ethnicity, 80.6% of infections were Caucasian, 9.2% Aboriginal, 2.0% Black, 2.0% Asian and 6.1% other. Of the chronic HCV cases with known race/ethnicity, 73.9% of infections were Caucasian, 9.1% Black, 8.2% Asian, 4.6% Aboriginal and 4.2% other. In Hamilton (Table 2.6b), region of birth was available for 56.3% of the 32 acute HCV cases and 25.7% of the 676 chronic HCV cases. The distribution of race/ethnicity among cases with known may not reflect the true distribution in Hamilton; however, the majority of cases were Caucasian. Race/ethnicity information in London (Table 2.6c) was available for 77.2% of the 57 acute HCV cases and 98.8% of the 401 chronic HCV cases. Of the acute HCV cases with known race/ethnicity, 90.9% of infections were Caucasian, and 9.1% Aboriginal. Of the chronic HCV cases with known race/ethnicity, 84.3% of infections were Caucasian, 6.1% Aboriginal, 4.3% Asian, 2.3% Black, and 3.0% other. 3.3 Modeled HCV prevalence and incidence in Ontario, 2007 Tables 3.1a and 3.1b present the estimated prevalence of HCV infections by place of birth, sex and exposure category. Overall, among 12,885,750 persons living in Ontario as of December 2007, an estimated 109,717 were infected with hepatitis C, for a prevalence rate of 0.85% or about one in 117 persons. Persons born in Canada accounted for 79,051 (72%) of these infections compared to 30,667 among immigrants. The prevalence rate in persons born in Canada was slightly higher than that among immigrants (0.86% compared to 0.83%). 60% of prevalent HCV infections were among males, who had a prevalence rate 1.5-fold higher than that of females. Not surprisingly, the majority of prevalent HCV infections were among injection drug users. Current and ex-idus accounted for 54% of the HCV-infected persons in Ontario. Persons who 13

14 were infected through receipt of a blood transfusion accounted for 11% of HCV infections, hemophilia patients less than 1% and persons infected by other routes of transmission, 35%. In the model, 2,414 HCV-infected persons were also infected with HIV. IDUs accounted for 96% of the HCV-HIV co-infected persons. Note that this estimate does not include all persons with HCV-HIV coinfection in Ontario. Table 3.2 presents the estimated number of incident HCV infections by place of birth, sex and exposure category in calendar year Overall, 3,470 persons in Ontario were newly infected with HCV in 2007, for an overall incidence rate of 0.027% or about one in 3,680 persons. 2,250 (65%) of new HCV infections occurred in men, who had an incidence rate almost double that of women (0.036% compared to 0.019%). As expected, 80% of new HCV infections occurred in active injection drug users. Table 3.3 shows the modeled HCV prevalence number and rate by health region and public health unit in HCV prevalence varied substantially by public health unit but not by health region. Nevertheless, HCV prevalence was highest in the Eastern other and Toronto health regions with 1.36% and 1.07%, respectively, and lowest in the Central East other region at 0.70%. HCV prevalence varied considerably by public health unit, from a low of 0.27% in Huron to a high of 3.47% in Kingston. The rate in Kingston was 2.4 times higher than the next highest public health unit. In eight public health units, the HCV prevalence rate was 1.0% or greater and in four public health units, it was less than 0.50%. HCV prevalence was 0.50% to 0.99% in the remaining 24 public health units. Table 3.4 presents the modeled incidence of sequelae of HCV infection in Ontario from 1967 to In 2007, 359 persons developed cirrhosis, 216 persons progressed to decompensated liver failure, 135 cases were diagnosed with hepatocellular carcinoma and 61 persons received a liver transplant due to their HCV infection. In all, 223 persons died of HCV-related causes in According to our model, the incidence of cirrhosis increased from 1967 to 1997, was relatively stable at around 360 new cases annually from 1997 to 2012 and will decrease slightly in subsequent years. However, the incidence of the more advanced sequelae and mortality due to HCV will continue to increase over the entire study period. The number of deaths from all HCV-related causes is projected to increase from 223 in 2007 to 291 in 2027, an increase of 31%. Table 3.5 presents the modeled prevalence of sequelae of HCV infection in Ontario from 1967 to This table presents the total number of persons living with each complication of HCV infection; thus, the estimates are not mutually exclusive. In 2007, an estimated 7,330 persons were living with cirrhosis, 2,525 in decompensated liver failure, 157 persons diagnosed with hepatocellular carcinoma and 549 post-transplant patients. According to our model, the prevalence of the sequelae of HCV infection will continue to increase in future. The most dramatic increase is projected among post-transplant patients, from 549 in 2007 to 914 in 2027, an increase of 66%. 14

15 4. DISCUSSION Hepatitis C became a reportable disease in Ontario in October Overall, 97,392 HCV infections were reported to the Ontario reportable disease surveillance system from 1992 to In the most recent six years from 2005 to 2010, about 4,500 new HCV cases were reported annually of whom 62% were male. The annual rate of reported HCV cases was per 100, 000 population, much higher among males (40-48 per 100,000) than females (23-29 per 100,000). According to data from EHSSS from 2007 to 2010, the total number of reported HCV cases was 1,031 in Ottawa, 715 in Hamilton, and 419 in London. For acute HCV infections alone, it was 119 in Ottawa, 32 in Hamilton, and 57 in London. IDU was the predominant risk factor for HCV infection in all three sites. During this period, 25% of HCV infections in Ottawa and 15% in London were from minority population groups. Statistical modeling revealed that, as of December 2007, 109,717 persons in Ontario were infected with hepatitis C, and 3,470 new infections occurred in HCV incidence among men overall was 0.036%, almost twice that among females with 0.019%. Of the almost 110,000 HCV-infected persons in Ontario, 21,632 (20%) were active IDUs and 37,253 (34%) past IDUs, 12,025 (11%) had been infected through blood transfusion, 372 (0.34%) were hemophilia patients and 38,436 (35%) were infected through other modes of transmission, including sexual, occupational, nosocomial and vertical transmission. HCV prevalence varied considerably by public health unit but to a lesser degree by health region. The largest number of HCV-infected persons (27,888, or 25%) were resident in Toronto, with the next highest being Ottawa, with 7,380 prevalent HCV infections. However, the rate varied substantially by public health unit, from a high of 3.47% in Kingston to a low of 0.27% at the Huron County Public Health Unit. The impact of the sequelae of hepatitis C infection on the health of persons in Ontario appears to be considerable. In 2007, 7,330 persons were living with cirrhosis, 2,525 were in liver failure, 157 had been diagnosed with hepatocellular carcinoma and 549 were post-transplant patients. The annual incidence of new cases of cirrhosis appeared to plateau in 1997 but, according to the results of our model, the incidence of the more serious outcomes of HCV infection will continue to rise, at least until Liver deaths, for example, increased from only 12 in 1967 to 291 in 2027, increasing approximately 30% from 2007 to Due to limitations in our data and analytic methods, the results in the present report should be interpreted with caution. Data on reported cases of HCV in Ontario do not distinguish acute from chronic infections, risk factor information was not systematically collected, and it is unclear whether a significant number of duplicate cases remain in the data. EHSSS data provides more detailed and reliable risk factor information and attempts to differentiate between acute and chronic infections. However, currently, only some cities in Ontario have been participating in the surveillance system, which comprised fewer than 20% of reported HCV cases in Ontario 15

16 from 2005 to Toronto has been recently added to the network and this should provide important new data over the coming years. The modeled HCV estimates are hypotheses, not conclusions, based on several assumptions. The explanation of these assumptions and limitations of the modeling methods have been described in detail in the previous report <4>. With regard to demographic characteristics, data on births, deaths and census populations were relatively precise and therefore not subject to significant uncertainty. Immigration figures were derived from the Canadian model multiplied by the proportion of Canadian immigrants who settled in Ontario. This is also relatively reliable. However, to determine the prevalence of HCV infection in immigrants, the research team relied on HCV in the country of origin as reflected by the occurrence of HCV among persons not born in Canada in the EHSSS database. It is unclear how precise the country birth data is in this database. The model developed by Remis incorporates assumptions about the likely incidence and prevalence of HCV in key populations. The results of the model are based on data derived from epidemiologic studies and from the EHSSS surveillance project implemented by the Public Health Agency of Canada. However, no population-based data on HCV prevalence or incidence is available in Ontario. It is hoped that population-based surveys will be carried out in the near future to provide empirical estimates of HCV prevalence. The EHSSS also has limitations related to incomplete and biased data. These are discussed more fully in the report of HCV in Canada in 2002 <3>. Risk factor data were not systematically available from reported cases, which would have helped to assess indirectly the relative infection rates in the principal groups at risk for HCV. 16

17 References 1. Choo QL, Kuo G, Wiener AJ, et al. Isolation of a cdna clone derived from a blood-borne non-a, non-b viral hepatitis genome. Science, 1989, 244: Cranston, L. Building a better blood system for Canadians. Canadian Journal of Public Health, 2000, 91(Supplement):S Remis RS, Palmer RWH, Hershfield NC. A study to characterize the epidemiology of hepatitis C infection in Canada, September 2003 [Technical report for Hepatitis C Division, Centre for Infectious Disease Prevention and Control, Health Canada]. 4. Remis R. The Epidemiology of Hepatitis C Infection in Ontario, Final Report. Toronto: Hepatitis C Secretariat, Community Health Division, Ontario Ministry Of Health and Long Term Care; Remis R. The Epidemiology of Hepatitis C Infection in Ontario, update to Final Report. Toronto: Hepatitis C Secretariat, Community Health Division, Ontario Ministry of Health and Long Term Care; Ontario Public Health Standards Accessed at: stds/pdfs/ophs_2008.pdf 7. Zou S, Zhang J, Tepper M, et al. Enhanced surveillance of acute hepatitis B and C in four health regions in Canada, 1998 to Canadian Journal of Infectious Diseases, 2001, 12: Wu HX, Wu J, Wong T, et al. Enhanced surveillance of newly acquired hepatitis C virus infection in Canada, Scandinavian Journal of Infectious Disease, 2006, 38:

18 Table 1.1 Number and rate (per 100,000 population) of reported cases of hepatitis C, Ontario, Year Annual HCV case reports Rate (per 100,000 population) , , , , , , , , , , , , , , , , , , , Sources: Public Health Agency of Canada ( ) Public Health Division, Ontario Ministry of Health and Long-Term Care ( ) Population estimates provided by Statistics Canada. Table Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annually 18

19 Table 1.2 Reported cases and rate 1 of hepatitis C by year and sex Ontario, Year Number of cases Rate 1 Male Female Total Male Female Total ,944 1,623 4, ,554 1,447 4, ,769 1,820 4, ,816 1,887 4, ,802 1,769 4, ,736 1,645 4, Rate per 100,000 population Sources: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [2011/03/21] for and [2011/02/14] for 2010 Population estimates provided by Statistics Canada. Table Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annually 19

20 Table 1.3a Number and proportion 1 of reported cases and rate 2 of hepatitis C by age and sex, Ontario, 2005 Male Female Total Age Number % 1 Rate 2 Number % 1 Rate 2 Number % 1 Rate % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 14.6 Unknown Total 2, % , % , % Column percent among known 2. Rate per 100,000 population Sources: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [2011/03/21] for and [2011/02/14] for population estimates provided by Statistics Canada. Table Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annually 20

21 Table 1.3b Number and proportion 1 of reported cases and rate 2 of hepatitis C by age and sex, Ontario, 2006 Male Female Total Age Number % 1 Rate 2 Number % 1 Rate 2 Number % 1 Rate % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 11.5 Unknown Total 2, % , % , % Column percent among known 2. Rate per 100,000 population Sources: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [2011/03/21] for and [2011/02/14] for population estimates provided by Statistics Canada. Table Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annually 21

22 Table 1.3c Number and proportion 1 of reported cases and rate 2 of hepatitis C by age and sex, Ontario, 2007 Male Female Total Age Number % 1 Rate 2 Number % 1 Rate 2 Number % 1 Rate % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 15.6 Unknown Total 2, % , % , % Column percent among known 2. Rate per 100,000 population Sources: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [2011/03/21] for and [2011/02/14] for population estimates provided by Statistics Canada. Table Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annually 22

23 Table 1.3d Number and proportion 1 of reported cases and rate 2 of hepatitis C by age and sex, Ontario, 2008 Male Female Total Age Number % 1 Rate 2 Number % 1 Rate 2 Number % 1 Rate % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 13.3 Unknown Total 2, % , % , % Column percent among known 2. Rate per 100,000 population Sources: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [2011/03/21] for and [2011/02/14] for population estimates provided by Statistics Canada. Table Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annually 23

24 Table 1.3e Number and proportion 1 of reported cases and rate 2 of hepatitis C by age and sex, Ontario, 2009 Male Female Total Age Number % 1 Rate 2 Number % 1 Rate 2 Number % 1 Rate % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 12.7 Unknown Total 2, % , % , % Column percent among known 2. Rate per 100,000 population Sources: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [2011/03/21] for and [2011/02/14] for population estimates provided by Statistics Canada. Table Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annually 24

25 Table 1.3f Number and proportion 1 of reported cases and rate 2 of hepatitis C by age and sex, Ontario, 2010 Male Female Total Age Number % 1 Rate 2 Number % 1 Rate 2 Number % 1 Rate % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 16.0 Unknown Total 2, % , % , % Column percent among known 2. Rate per 100,000 population Sources: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [2011/03/21] for and [2011/02/14] for population estimates provided by Statistics Canada. Table Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annually 25

26 Table 1.4a Number and proportion 1 of reported cases and rate 2 of hepatitis C by public health unit and sex, Ontario, 2005 Male Female Total PHU N % 1 Rate 2 N % 1 Rate 2 N % 1 Rate 2 Toronto % % , % 44.7 Ottawa % % % 32.2 Algoma % % % 54.0 North Bay-Parry Sound % % % 36.3 Northwestern % % % 47.1 Porcupine % % % 28.1 Sudbury % % % 38.9 Thunder Bay % % % 90.8 Timiskaming % % % 25.3 Northern region % % % 50.0 Eastern Ontario % % % 30.2 Hastings-Prince Edward % % % 36.4 Kingston-Frontenac-Lennox -Addington % % % Leeds-Grenville-Lanark % % % 35.0 Renfrew % % % 21.5 Eastern, other region % % % 56.4 Durham % % % 40.1 Haliburton-Kawartha-Pine Ridge % % % 57.9 Peel % % % 29.3 Peterborough % % % 40.2 Simcoe-Muskoka % % % 21.8 York Region % % % 28.3 Central East, other % % , % 31.7 Brant % % % 35.6 Hamilton % % % 18.2 Haldimand-Norfolk % % % 37.6 Halton % % % 25.9 Niagara % % % 53.1 Waterloo % % % 27.9 Wellington-Dufferin-Guelph % % % 19.0 Central West region % % % 29.9 Chatham-Kent % % % 28.5 Elgin-St. Thomas % % % 20.6 Grey Bruce % % % 32.6 Huron % % % 11.4 Lambton % % % 30.2 Middlesex-London % % % 31.1 Oxford % % % 21.7 Perth % % % 11.7 Windsor-Essex % % % 31.6 Southwest region % % % 28.2 Total 2, % , % , % Column percent 2. Rate per 100,000 population Sources: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [2011/03/21] for and [2011/02/14] for population estimates provided by Statistics Canada. Table Estimates of population (2006 Census and administrative data), by age group and sex, Canada, provinces, territories, health regions (2007 boundaries) and peer groups, annually (Number) 1996 to