The Reproductive Care of Women Living With Hepatitis C Infection

III. Epidemiology

A. Prevalence and Incidence

1. General population

In a recent publication,⁸ the World Health Organization (WHO) estimated that in 1999, 170 million persons were infected with HCV, representing approximately three percent of the world's population. Reported seroprevalence rates in the general population vary greatly throughout the world, although accurate and properly collected data are missing from numerous areas of the globe.

• TABLE I : DATA FOR THE GENERAL POPULATION IN CANADA9,10
  	Number of patients	% population
  Estimated prevalence	240,000 (range 210,000-275,000)	0.8%
  Estimated annual incidence	1,000*
  * clinically recognized acute cases

Notification of hepatitis C in Canada began in 1992 and has been mandatory in all provinces since January 1999. The number of reported cases has increased ramatically since then, which may in part be due to reporting bias. However, there also appears to be an actual increase in incidence of identified cases, as suggested by numbers from British Columbia, where reliable reporting has existed since the early 1990's: numbers are still showing an annual rise. This is perhaps not surprising, given that the progression of this chronic disease is usually slow. Indeed it may not manifest in the first two decades of infection, and many cases in Canada may have been acquired in the remote past. The rise may also be related to factors such as increased availability of testing, improved sensitivity of tests, and a greater public awareness of the disease, leading to an alteration in test seeking behaviours. The total number of notifications across Canada has risen from 1,321 in 1992 to 19,571 in 1997. For women of all ages the notifications have risen from 482 in 1992 to 6,977 in 1997.²

• TABLE II : PREVALENCE OF HCV IN HIGH RISK GROUPS IN CANADA
  High Risk Groups in Canada	Prevalence of HCV (%)
  Injection drug users after one year	70
  Aboriginal populations (preliminary data)	15-20
  Haemodialysis patients	*
  Recipients of blood products, tissue, organs from 1960-92	1.5-2.7
  Prisoners in correctional facilities11 (women in Kingston: 86.9% tested) (men in western Canada: 23% tested)	39.8 25
  * No Canadian data available

Certain population subgroups are at much higher risk of being infected with HCV. In 1994, 71 percent of individuals with HCV had a history of using injection drugs and 28 percent a history of blood transfusion.⁴⁹ Interim data from a recent LCDC study of Canadian street youth showed 4.4 percent (range 0-9.2%) of individuals tested to be positive for HCV⁵⁰ and a similar study in Montreal, a prevalence of 12.6 percent (95% CI: 9.7-15.9%).⁵¹ Preliminary data suggests that aboriginal populations, both urban and rural, have a 15 to 20 percent positivity rate for anti-HCV antibodies.⁵²

2. Pregnant population

Many series of anti-HCV antibody seroprevalence in pregnant women have been published around the world, some of which have also taken into account the co-existence of human immunodeficiency virus (HIV) (Table III).

However, there is very little published data for seroprevalence and incidence of hepatitis C infection during pregnancy in Canadian women. The only serosurvey of a general population of pregnant women in Canada was done on 15,000 prenatal sera in British Columbia in 1994 and reported a seroprevalence rate of 0.9 percent (95% CI: 0.76-1.1%⁵³). Unpublished data from Vancouver suggests that up to 54 percent of women with HIV are also infected with HCV.⁵⁴ The majority (63%) of these HIV positive women are injection drug users.⁵⁴ In Montreal, however, the percentage of injection drug users is smaller (18.5%) with the majority of HIV positive women coming from endemic countries (57.4%). In this last cohort, the prevalence of positive hepatitis C serology is 21 percent.⁵5

A study of non-pregnant women of childbearing age in Canada reported a prevalence of 0.58 percent. An extrapolation from data obtained from the current population of new blood donors in Canada would suggest a seroprevalence of 0.2 percent.⁵⁶ However, it is doubtful that this figure could be applied directly to a population of pregnant women.

There is some data to suggest that women from aboriginal populations and inner city groups are over-represented in infected cases. The prevalence of HCV infection is highest in the 20 to 24 year age group and 50 percent more prevalent in urban areas compared with rural. However, as yet, this data is incomplete.

B. Mode of Transmission

Table IV lists sources of acquisition of HCV identified by the World Health Organization.⁸ It is important to remember that immigrants may have encountered either unusual or exposureprone procedures with a higher risk prior to arriving in Canada. A proportion of patients with HCV do not fall into any currently recognized risk group.

Tests for HCV became commercially available for use in 1990, facilitating the demonstration of hepatitis C transmission routes.⁵⁷ These routes are similar to those for other bloodborne pathogens such as hepatitis B virus (HBV) and HIV, although the frequencies differ. However, the individual risks for some of these routes still need to be accurately defined. The risk of a person becoming infected with HCV will depend on the type of exposure.

• TABLE III : POPULATION STUDIES SHOWING SEROPREVALENCE OF HEPATITIS C DURING PREGNANCY: GENERAL POPULATION AND POPULATION STRATIFIED ACCORDING TO HIV STATUS.
  YEAR OF PUBLICATION	COUNTRY	TOTAL ANTI-HCV POSITIVE	HIV POSITIVE WOMEN	HIV NEGATIVE WOMEN
  1992	É.-U. (New York)12	29/648 (4.5%)	NR*	NR
  1992	Haïti (milieu rural)13	2/500 (0.4%)	NR	NR
  1992	É.-U. (Dallas)14	23/1,005 (2.3%)	NR	NR
  1992	Italie (Rome)15	10/1,142 (0.9%)	NR	NR
  1993	Japon (Kuruke)16	26/1,661 (1.6%)	NR	NR
  1993	France (Paris)17	41/2,367 (1.7%)	NR	41/2,367 (1.7%)
  1993	France (Clichy)18	13/670 (1.9%)	NR	13/670 (1.9%)
  1993	É.-U. (Philadelphie)19	26/599 (4.3%)	2/3 (66.7%)	24/596 (4.0%)
  1994	Taiwan (Taipei)20	40/2,020 (2.0%)	NR	40/2,020 (2.0%)
  1994	Japon (multicentre)21	53/7,698 (0.7%)	NR	NR
  1994	Cameroun (Yaounde)22	26/384 (6.8%)	NR	NR
  1994	Italie (Vicenza)23	24/5,672 (0.4%)	NR	NR
  1995	É.-U. (San Juan, PR)24	19/997 (1.9%)	1/8 (12.5%)	18/989 (1.8%)
  1995	Japon (Tsukuba)25	29/2,380 (1.2%)	NR	NR
  1995	Italie (Milan)26	250/21,516 (1.2%)	NR	NR
  1995	É.-U. (Philadelphie)27	47/1,432 (3.2%)	NR	NR
  1995	Japan (multicentre)28	163/16,714 (0.98%)	NR	NR
  1995	Italy (Torino)29	35/5,000 (0.7%)	NR	35/5,000 (0.7%)
  1996	Guinea (Conakry)30	8/302 (2.6%)	NR	NR
  1996	Italy (Padova)31	29/1,700 (1.7%)	NR	NR
  1996	Italy (Chieti)32	30/2,980 (1.0%)	NR	30/2,980 (1.0%)
  1996	Italy (Udine)33	36/1,388 (2.5%)	NR	NR
  1997	Spain (Seville)34	59/6,556 (0.9%)	NR	NR
  1997	United Arab Emirates (Al-Ain)35	65/499 (13.0%)	NR	65/499 (13.0%)
  1997	Japan (Kurume)36	23/1,661 (1.4%)	NR	NR
  1997	Australia (Adelaide)37	17/1,488 (1.1%)	NR	NR
  1998	Italy (Genoa)38	NR	NR	82/7,023 (1.2%)
  1998	USA (multicentre)39	NR	169/511(33.1%)	NR
  1998	Malawi (rural setting)40	NR	6/50 (12%)	18/100 (18.0%)
  1998	Italy (Florence)41	NR	NR	442/25,654 (1.7%)
  1998	Japan (Tochigi)42	NR	NR	72/1,941 (3.7%)
  1998	Egypt (Mansoura)43	105/767 (13.7%)	NR	105/767 (13.7%)
  1998	Spain (Granada)44	16/3,003 (0.5%)	NR	NR
  1998	Italy (Florence)6	NR	NR	80/5,000
  1999	Tanzania (Ifakara)45	49/980 (5.0%)	1/66 (1.5%)	48/914 (5.3%)
  1999	Italy (Monza)46	63/16,271 (0.4%)	NR	NR
  1999	India (rural setting)47	0/46 (0.0%)	NR	NR
  2000	Italy (Milan, Bergamo)48	370/15,250 (2.4%)	NR	NR

1. Injection drug use

The most significant mode of transmission of hepatitis C in Canada now is injection drug use. The rate of infection in those who have ever used injection drugs is at least 30 percent.^1,3,58 Up to two thirds of users seroconvert within the first year of use. HCV is not only associated with chronic use and may be contracted even by those who have injected only a few times. The evidence for transmission with the use of inhaled drugs, such as intranasal cocaine, is controversial. It is not clear whether this is an independent mode of transmission via shared use of contaminated straws or a marker for injection drug use.

• TABLE IV : SOURCES OF ACQUISITION OF HEPATITIS C VIRUS

  High Risk (over 20%) • Injection drug users • Recipients of unscreened blood products • Transfusion of blood products that did not undergo viral inactivation

  Moderate Risk (1-20%) • Newborns of HCV positive mothers • Persons undergoing chronic haemodialysis • Recipients of blood from unscreened donors • Recipients of organ transplants • Parenteral exposure through the use of contaminated or inadequately sterilized instruments/needles in medical/dental procedures

  Low risk (below 1%) • Persons engaged in high risk sexual activity • Sexual partners of HCV positive individuals • Rituals (such as circumcision, scarification, excision), traditional medicine (such as blood letting), other skin breaking activities (such as ear and body piercing) • Tattooing not carried out in properly regulated premises • Household contact

2. Blood/blood product transfusion

In Canada the risk of infection through blood transfusion has been reduced, although not eliminated, by the testing of donors for HCV. In fact, even prior to 1990 and the introduction of screening, the risk had started to fall because of changes in donor screening practices. After testing for hepatitis B became available in the early 1970's, the virus that was later identified as hepatitis C became the most common cause of post-transfusion hepatitis. Currently the risk stands at one in 103,000 per unit of blood transfused, with the likelihood of further reduction as the more sensitive nucleic acid testing is introduced (Table V).² However, it must be remembered that in some countries with a higher prevalence in the donor population, the risk may be greater depending on the testing modalities used. The chance of becoming infected with HCV from an infected unit is over 90 percent.

• TABLE V : CHANGE IN INCIDENCE OF POST-TRANSFUSION HEPATITIS
  	Incidence
  Mid 1980's	3.1% per transfusion event*
  Late 1980's	1.3% per transfusion event*
  Early 1990's	0.6 per 1,000 blood units tranfused, 0.5%-0.8% HCV+**
  Present	1 in 103,000 per blood unit transfused
  * receipt of transfusion with mean of 3.5 units ** personal communication with Canadian Blood Services

3. Needle stick injury with an HCV contaminated sharp

The occurrence of infection after a needle stick accident with an HCV contaminated sharp has been reported as about four percent (see Section IX: Occupational Exposure).

4. Vertical transmission

For the risk of transmission from mother to child please refer to Table VI, although caution should be applied in interpreting some of the early data. The risk of vertical transmission ranges from zero to 80 percent. Merging the data from these studies gives a crude vertical transmission rate of 7.9 percent (179/2,264). If the mother is co-infected with HIV, the risk of HCV transmission has been observed to increase up to 60 percent. Vertical transmission seems to be directly related to the presence of circulating HCV RNA in the maternal blood during pregnancy.^7,32,59-61

5. Breastfeeding

A few researchers have reported the presence of HCV RNA in breast milk. When present, it has been in much lower concentrations than in the blood. The importance of these findings is not yet clear and while there is a theoretical risk of transmission, no case has yet been reported (see Section V.B.7: Breastfeeding and VII. D: Principles of prescribing in HCV infected women).^36,62

6. Sexual transmission

The risk of sexual transmission is very low. HCV has been found infrequently in semen of men co-infected with HIV. The rate of transmission has been controversially estimated at about 2.5 percent for prolonged sexual exposure ( >20 yrs) to infected individuals. There are many cohorts of haemophiliacs and their partners with supporting negative data. Another study found that having had intercourse with an injection drug user was independently predictive of HCV infection. Women with multiple sexual partners may be more likely to acquire HCV; a study looking at prostitutes not using condoms reported a higher incidence of HCV, even adjusting for IVD use.⁶³ There is no data for transmissibility during menstruation or anal intercourse, although it is noted that in homosexual men, the transmission rates are not comparable to those those of HIV. Similarly, the risk of transmission with the shared use of sex toys is unknown. There is no data on the risk for lesbian transmission, although there is some data suggesting that the rates in women with HIV are very low and are, therefore, likely to be lower still with HCV.

7. Rhimmunoprophylaxis

Studies of two large cohorts of women infected following contaminated Rh immunoprophylaxis documented a lack of transmission after 7,000 person-years of unprotected sexual activity, again supportive of a minimal risk.⁶⁴ The currently used preparation for Rh immunoprophylaxis (Winrho SDF™ as well as the previously used Winrho™) is devoid of risk from known viral bloodborne pathogens, including HCV, due to modern purification processes.

8. Transmission between family members, household contact

General household contact is not thought to be a risk. Where familial transmission has been observed, such transmission may have been due to inadvertent blood contact (razor, toothbrush), but there is no evidence to implicate the use of these items. HCV antibodies and HCV RNA have both been detected in saliva. However, they are not predictably present and the implications for transmission are not clear.

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