The spectrum of the source of infection with hepatitis C has changed with the advent of testing all blood donors for hepatitis C beginning in 1990. Intravenous drug use is the most common route of infection. Many patients, however, have more than one risk factor. Up to 20% of patients who have had a previous blood transfusion have also used intravenous drugs and there is a high rate of intravenous drug use among highly sexually promiscuous persons.
Routes of transmission may be different in different geographical areas. For instance, some years ago common needles and syringes were used for mass vaccination in some European countries such as Italy.
The finding of hepatitis C by PCR in certain body fluids does not mean that this is a route of infection. Tears, for example, have been shown to test HCV RNA positive by PCR, but it has never been shown that tears have transmitted hep C.
Hep C has an increased incidence in alcoholics regardless of other factors, the reason for this is unknown.
As will be further discussed, the anti-HCV test is a test for an antibody, and does not differentiate the 20% of persons who have recovered after the acute attack from the 80% who have developed chronic hepatitis C. The HCV RNA as measured by PCR determines the presence of persistent viremia.
Transmission Rates: Canada
Recent studies suggest that the route of transmission can be determined in 90% of patients.
Route: % of patients
– blood or blood products (prior to 1990) 27%
– intravenous drug use 43 – 58%
– intra-nasal cocaine 4 – 10%
– sexual promiscuity 17%
– ear/body piercing, tattoos 1 – 5%
– unknown 10%
(Routes of infection are not exclusive)
Studies have shown that:
– In persons contracting hep C through blood transfusions, the more units of blood transfused the more likely to have contracted hep C.
– In IVDU’s the positivity rate increases with years of use and by 10 years 70% of IVDU’s are positive for hep C.
– people using intra-nasal cocaine or “snorting” often share the same straw, are very likely to break small intra-nasal blood vessels and transmit hep C this way.
Special Risk Groups
Certain risk groups have increased incidence of hep C :
– maternal to fetal – maximum of 8%
– needle prick injury – 8 – 10%
– health care workers – 1.5% = same as general population
– hemophiliacs – about 60% but many are co-infected with HIV
1. IV drug users often claim they use only clean needles. Often memory is not good under the influence of drugs, particularly cocaine. Hep C may also be transmitted by sharing the “rigs” even though the actual needle may not be shared.
2. Studies have shown maternal to neonate (at time of birth) to be a maximum of 8%, most studies actually showing about 6%. Intra-uterine transmission is not thought to occur. Transmission is higher if the mother has a high viral load. Transmission is much more likely if the mother is also HIV positive. A cesarean section may reduce the risk even further. Note: the antibodies from the mother are transferred to the fetus and may remain present for up to 8 months after birth and thus, an infant will test antibody positive. If an infant is to be tested before 1 year he/she should be tested for HCV RNA by PCR. The infant may be tested for antibody after one year.
3. Sexual transmission is uncommon, and most studies suggest a lifetime risk for a sexual partner to be less than 6%. Sexual transmission is increased if another STD such as herpes genitalis is present. Couples should make their own decision about protection but in many circumstances it is not mandatory. Certainly at menstruation or if there are any bleeding sites, protection is advisable. Usually a partner of the contact patient tests negative and remains negative.
4. Breastfeeding has not been shown to transmit hep C. HCV RNA has been shown in low titres in colostrum, but the oral route has not been shown to be a means of hep C transmission. Mothers are advised they can breastfeed as long as there is no obvious bleeding from the nipples.
5. While HCV RNA has been shown in other body secretions such as tears, no documented transmission of hep C by other routes has been shown.
6. Interfamilial transmission has not been shown. Common sense should apply however, and household family members of a person with hep C should not share razors, tooth brushes, etc.
7. The best disinfectant for hep C is bleach. If contaminated blood is exposed it should be washed with bleach.
8. The present risk of contracting hepatitis C from a blood transfusion is 1 per 200,000 units of blood.
Who Should Be Tested ?
Note: Only 24% of persons testing positive for hep C had any idea that they might be positive. Wider testing is indicated.
The following should be tested:
– people who received blood or blood products, (gamma globulin, plasma, etc.) before 1990.
– all IV drug users.
– all sexually promiscuous persons
– all persons with tattoos done in other than very reputable parlors
– all partners of positive patient (low yield, however)
– needle stick injured persons from known contact case should be tested in 2 to 3 weeks post exposure using HCV RNA test (PCR).
– all persons with elevated Ast or Alt as part of overall investigation