In the developed world, the most common way that people get Hepatitis C is through intravenous drug use (by shooting drugs into a vein, using a needle that was already used by a person who has Hepatitis C). In the developing world, most people get Hepatitis C through blood transfusions (being given blood that was taken from a person with Hepatitis C) or by getting medical care with tools that were not cleaned enough after being used on a person with Hepatitis C. In 20% of all cases of Hepatitis C (or 1 in every 5 cases), it is not known what caused the infection, but many of these cases are thought to have been caused by intravenous drug use.
In many parts of the world, intravenous (IV) drug use (shooting drugs into a vein using a needle) is a major risk factor for Hepatitis C (meaning that it makes people more likely to get the disease). One study that looked at 77 countries showed that in 25 of these countries (including the United States), between 60% and 80% (or 6 to 8 out of every 10) of all IV drug users had Hepatitis C. and China. In twelve of the countries in the study, more than 80% of all IV drug users had Hepatitis C. Across the world, as many as ten million IV drug users are thought to have Hepatitis C; the highest totals are in China (1.6 million), the United States (1.5 million), and Russia (1.3 million). Studies have also shown that in places where there are high numbers of IV drug users, people are more likely to have Hepatitis C. For example, prisoners in the United States are ten to twenty times more likely than the general population (people in general) to have Hepatitis C. This is thought to be because prisoners are more likely to things that put them at high risk for getting Hepatitis C, like using IV drugs and getting tattoos with tools that have not been cleaned properly.
Peoples are at risk for getting Hepatitis C if they get blood transfusions (where a person is given blood from another person), blood products (which have blood or parts of blood in them), or organ transplants (where a person who needs a new organ is given an organ from another person), if these things have not been screened (or tested) for the Hepatitis C virus. In the United States, there has been universal screening - meaning that all blood and organs are tested before being given to another person - since 1992. Before then, about one out of every 200 units of blood carried the Hepatitis C virus; since 1992, only one in 10,000 to 10,000,000 units of blood carry the virus. The reason that there is still a low risk, instead of no risk at all, is that a person's blood does not test positive for the Hepatitis C virus until about 11–70 days after they get the disease. So every once in a while, the screening tests may not pick up on a person's infection if the person got Hepatitis C less than 11–70 days before giving blood. While Hepatitis C screening works very well, some countries still do not screen blood and organ donations for the disease because of the cost.
Sometimes, a healthcare worker will accidentally get stuck with a needle that was used on a person with Hepatitis C. If this happens, the healthcare worker has a small chance - about a 1.8% chance - of becoming infected. The worker is more likely to get infected if the needle they were stuck with was hollow, or if the needle stuck deeply into their skin It is also possible for the Hepatitis C virus to spread if an infected person's mucus touches another person's blood; however, the risk of this happening is low. The virus cannot be spread if an infected person's mucus touches another person's intact skin (skin that is whole and not damaged, with no wounds).
Hepatitis C can also be transmitted (or spread) through hospital equipment that has not been cleaned enough after being used on an infected person. Hepatitis C can be spread through needles, syringes, and medication vials (or containers) that are re-used; through infusion bags (which are used to pump medications into a person's body; and through surgical equipment that is not sterile (or clean and free of germs). In Egypt, which has the highest rate of infection in the world, medical and dental facilities with poor standards of care and cleanliness are the most common reason that Hepatitis C spreads.
Scientists do not know whether Hepatitis C can be transmitted (or spread) through sex. Hepatitis C is more likely in people who have high-risk sexual activity (sexual actions which make them much more likely to get Hepatitis C). However, it is not known whether this is because of these people's sexual behavior, or because these people were also using IV drugs. There does not seem to be any risk that Hepatitis C can be spread through sexual contact between a heterosexual couple (a man and a woman; commonly called a "straight" couple) if neither person has sex with anyone else. There does seem to be a risk of Hepatitis C spreading if one person already has a sexually transmitted infection, like HIV or genital ulceration; or if two people have sex in a way that causes wounds to the lining of the anal canal (like anal penetration - one person putting his penis into another person's anus). The United States government says that most people need to use condoms to protect themselves from getting Hepatitis C only if they have more than one sexual partner.
People who get tattoos are about two to three times more likely to get Hepatitis C. This can be because of tools that are not sterile (not clean or free of germs), or because the dyes used for tattooing are contaminated (the Hepatitis C virus has gotten inside of them).
Tattoos or body piercings that were done before the mid-1980s or by people who are not professionals (not experts) are especially likely to spread Hepatitis C, since they are more likely to have used tools that were not sterile. Bigger tattoos also seem to put a person at more risk of getting Hepatitis C. The risk of getting Hepatitis C is very high in prisons; in the United States, almost half of all prison inmates share tattooing tools that are not sterile. However, if a tattoo is done in a licensed place of business (which has to follow rules about cleaning tools and preventing diseases from spreading), there is almost no risk of getting Hepatitis C from the tattoo.
Because Hepatitis C is spread by blood-to-blood contact, personal-care tools which come into contact with blood - like razors, toothbrushes, and manicure or pedicure equipment or any other kind of blood to blood contact - can spread the disease if they are shared. To prevent the spread of Hepatitis C, people should be careful with cuts, sores, or anything else that causes bleeding. Hepatitis C does not spread through casual contact, such as hugging, kissing, or sharing eating or cooking utensils.
Although this does not happen very often, a pregnant woman who has Hepatitis C can give the disease to her baby when it is born, or to her fetus while she is pregnant. This happens in less than 10% of all pregnancies (less than 1 out of every 10 pregnancies). If a pregnant woman has Hepatitis C, nothing can be done to make her less likely to give her baby the disease. If the woman is in labor (the process of delivering her baby) for a long time, there is more of a chance that the baby will become infected during the birth. Breastfeeding does not seem to spread the disease. However, doctors say that an infected mother should not breastfeed if her nipples are cracked and bleeding, or her viral loads (the amount of the Hepatitis C virus in her blood) are high.