Transmission of Hepatitis C virus

Transmission

Hepatitis C infection in the United States by source

The primary route of transmission in the developed world is intravenous drug use (IDU), while in the developing world the main methods are blood transfusions and unsafe medical procedures.The cause of transmission remains unknown in 20% of cases; however, many of these are believed to be accounted for by IDU.

Intravenous drug use

IDU is a major risk factor for hepatitis C in many parts of the world. Of 77 countries reviewed 25 (including the United States) were found to have prevalences of hepatitis C in the intravenous drug user population of between 60% and 80%. Twelve countries had rates greater than 80%.It is believed that ten million intravenous drug users are infected with hepatitis C; China (1.6 million), the United States (1.5 million), and Russia (1.3 million) have the highest absolute totals. Occurrence of hepatitis C among prison inmates in the United States is 10 to 20 times that of the occurrence observed in the general population; this has been attributed to high-risk behavior in prisons such as IDU and tattooing with nonsterile equipment.

Healthcare exposure

Blood transfusion, transfusion of blood products, or organ transplantation without HCV screening carry significant risks of infection. The United States instituted universal screening in 1992and Canada instituted universal screening in 1990. This decreased the risk from one in 200 units to between one in 10,000 to one in 10,000,000 per unit of blood. This low risk remains as there is a period of about 11–70 days between the potential blood donor acquiring hepatitis C and their blood testing positive depending on the method.Some countries do not screen for hepatitis C due to the cost.

Those who have experienced a needle stick injury from someone who was HCV positive have about a 1.8% chance of subsequently contracting the disease themselves. The risk is greater if the needle in question is hollow and the puncture wound is deep. There is a risk from mucosal exposures to blood; but this risk is low, and there is no risk if blood exposure occurs on intact skin.

Hospital equipment has also been documented as a method of transmission of hepatitis C including: reuse of needles and syringes, multiple-use medication vials, infusion bags, and improperly sterilized surgical equipment, among others. Limitations in the implementation and enforcement of stringent standard precautions in public and private medical and dental facilities are known to be the primary cause of the spread of HCV in Egypt, the country with highest rate of infection in the world.

Sexual intercourse

Whether hepatitis C can be transmitted through sexual activity is controversial.While there is an association between high-risk sexual activity and hepatitis C, it is not known whether transmission of the disease is due to drug use that has not been admitted to or sex as a risk factor. The majority of evidence supports there being no risk for monogamous heterosexual couples.Sexual practices that involve higher levels of trauma to the anogenital mucosa, such as anal penetrative sex, or that occur when there is a concurrent sexually transmitted infection, including HIV or genital ulceration, do present a risk. The United States government only recommends condom use to prevent hepatitis C transmission in those with multiple partners.

Body modification

Tattooing is associated with two to threefold increased risk of hepatitis C. This can be due to either improperly sterilized equipment or contamination of the dyes being used. Tattoos or piercings performed either before the mid-1980s, "underground," or nonprofessionally are of particular concern, since sterile techniques in such settings may be lacking. The risk also appears to be greater for larger tattoos. It is estimated that nearly half of prison inmates share unsterilized tattooing equipment.It is rare for tattoos in a licensed facility to be directly associated with HCV infection.

Shared personal items

Personal-care items such as razors, toothbrushes, and manicuring or pedicuring equipment can be contaminated with blood. Sharing such items can potentially lead to exposure to HCV. Appropriate caution should be taken regarding any medical condition that results in bleeding, such as cuts and sores.HCV is not spread through casual contact, such as hugging, kissing, or sharing eating or cooking utensils.Neither is it transmitted through food or water.

Vertical transmission

Vertical transmission of hepatitis C from an infected mother to her child occurs in less than 10% of pregnancies. There are no measures that alter this risk. It is not clear when during pregnancy transmission occurs, but it may occur both during gestation and at delivery. A long labor is associated with a greater risk of transmission. There is no evidence that breast-feeding spreads HCV; however, to be cautious, an infected mother is advised to avoid breastfeeding if her nipples are cracked and bleeding, or her viral loads are high.

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