Causes and Risk Factors of Hepatitis C Virus

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Hepatitis C virus (HCV) is an infection that causes inflammation of the liver. It spreads through contact with an infected person's blood or body fluids. The most common ways that you could acquire HCV infection are through injected drug use, unprotected sex, a medical procedure using contaminated equipment, or through an injury or wound that exposes you to blood infected with HCV. 

hepatitis C risk factors

Common Causes

HCV enters the body and reproduces in the host's (infected person's) body, specifically targeting the liver. HCV often evades the body's immune system and causes disease as a result of direct attack on the liver. The body's own immune system response also produces harmful inflammation of the liver.

The liver is responsible for many body functions, such as blood clotting, digestion, food absorption and metabolism, so this is why HCV has such a wide impact on the body. 

There are several known mechanisms by which HCV invades the body.  

Injected Drug Use

Sharing needles, syringes, or the other equipment to inject drugs places you at extreme risk for developing HCV. Intravenous drug use is responsible for most of the HCV infections in the United States. 

The course of HCV illness may be different for those who acquire the infection through drug use than it is for people who acquire the infection in other ways. The reasons for this are unclear, but people who are frequently re-exposed to the virus through repeated drug use are more likely to become infected again after having been treated. 

Sexual Contact

Hepatitis C can spread through sexual contact, but it doesn't happen often. Unlike the hepatitis B virus, which is known to be present in semen and vaginal fluids, HCV is not found in significant amounts in these fluids. The risk of developing HCV from sexual contact is increased if you have multiple sexual partners, have direct contact with blood, have a sexually transmitted disease, or are infected with HIV.

It is difficult to quantify the number of people who acquire hepatitis sexually versus other means. One study found that long-term monogamous partners of someone infected with hepatitis C became infected around 4 percent of the time. 

There has been research looking into whether gay men are at higher risk of HCV, and studies show that the population may be at higher risk of acquiring HCV in certain circumstances, such as unprotected sex with an infected partner. 

Mother-Infant Transmission

Only about 4 to 8 percent of infants born to mothers with hepatitis C will be infected with the virus. This is called vertical spread. The risk of vertical spread nearly doubles if the mother also has HIV or has a higher viral load (high amount of virus in her body) at the time of delivery. C-section does not seem to increase the risk of transmission, but prolonged rupture of membranes during delivery is associated with an increased risk of mother-to-child transmission of HCV. 

Nearly all children born to mothers with HCV have antibodies for the virus. This does not mean that the child is infected.

Antibodies are immune proteins produced by the body in response to disease-causing agents like HCV, and these immune proteins are transmitted to young babies from their mothers.

There is no evidence to suggest that breastfeeding can increase the risk of HCV transmission from mother to child. In fact, the Centers for Disease Control and Prevention (CDC) and the American Congress of Obstetrics and Gynecologists (ACOG) endorse breastfeeding for mothers with HCV.

Needlestick Injuries in Healthcare Settings

Nurses, physicians, and all healthcare professionals who routinely use needles while providing medical care are at risk for needlestick injuries. In fact, it is estimated that more than 600,000 needlestick injuries happen each year, with nurses being at highest risk. An average of about 2 percent of needlestick injuries where there has been exposure to the virus will result in acute hepatitis C.

Blood Transfusion

In the past, blood transfusion was a common way HCV was widespread. People who had hemophilia, thalassemia, or other disease requiring multiple transfusions were especially at risk for exposure. However, today, exposure to HCV through blood transfusions is very rare because donated blood is tested for HCV antibodies as well as HCV genetic material.

Experts believe that your chance of getting HCV from a blood transfusion is about one in 2 million.

Medical Procedures

Some medical procedures, such as organ transplants, can also expose you. As with blood transfusions, organ donors are tested for the virus as well as for antibodies, making the risk extremely low. Vaccinations with contaminated needles may also expose people to HCV. This is not common in developed countries because disposable needles are normally used. 

Household Contact

HCV may spread within a household, but this is rare. Living with someone who has HCV will slightly increase your chances of exposure to the virus. The risk of this type of spread can be reduced by taking certain precautions. For example, since razors and toothbrushes can, in theory, be a source of HCV exposure, it is a good idea not to share these items.

Some estimates indicate that 10 percent of acute hepatitis and 30 percent of chronic hepatitis result from unknown exposures.

Most experts believe that this type of spread comes from contact with a contaminated wound, a forgotten high-risk contact with someone infected with HCV, or exposure to HCV from a medical procedure. 

Because many people have developed hepatitis C without being exposed to any known risk factors, it is now recommended that all adults born between 1945 and 1965 be tested.


There are several lifestyle risk factors that can increase your chances of becoming infected with HCV. These lifestyle factors increase your chances of coming into contact with contaminated blood. 

  • Tattooing or Body Piercing: Some tattoos are placed using needles that have not been properly cleaned, potentially increasing the risk of HCV. 
  • Injected Drug Use: Injecting any kind of drug into the skin, veins (IV), or muscles can increase your chances of acquiring HCV if you share needles. 
  • Unprotected Sexual Activity: Sexual activity without the use of condoms or when sexual activity involves contact with blood, there is an increased risk of HCV.  
  • Drug Use: A study showed that use of drugs or sexual partying associated with drug use may increase sexual risk. This risk appears to be separate from the risk of infection through injected drug use.  
  • Healthcare Workers: Healthcare workers can become infected, especially when caring for patients in conditions that are not sanitary. 
  • Medical and Cosmetic Procedures: Procedures that are done in a non-accredited environment may increase the chances of becoming infected with contaminated equipment. 
  • Casual contact: There is no evidence that casual contact, in general, spreads hepatitis C. Casual contact includes kissing, sneezing, hugging, coughing, sharing food or water, sharing eating utensils or drinking glasses.

Heath Risks

There is no genetic tendency of acquiring HCV or of developing a more severe infection. The only health factor associated with HCV is immune system deficiency, which makes it difficult for your body to fight off the infection. The immune deficiency most often noted with HCV is HIV infection. 

HIV, like HCV, can be acquired through injected drug use with contaminated needles and by sexual contact. The immune deficiency of HIV can make it more difficult for your body to fight off HCV infection. In addition, you may need antiviral medications for each infection, which can make treatment decisions somewhat more complicated if you are co-infected.

Frequently Asked Questions

  • What causes hepatitis C?

    Hepatitis C is caused by the hepatitis C virus (HCV), which primarily attacks liver cells. While many acute hep C infections will spontaneously resolve with no long-term consequences, more than half will become chronic and cause progressive damage to the liver over the course of years.

  • How is hepatitis C spread?

    The hepatitis C virus is primarily spread through percutaneous (through the skin) exposure to infected blood. Injecting drug use is a major cause of transmission. HCV can also be passed from mother to child during pregnancy and potentially through sex. Tattooing, piercing, and blood transfusions are unlikely causes of transmission in the United States.

  • What are the risk factors for hepatitis C?

    Risk factors for hepatitis C include:

    • Sharing needles and other drug paraphernalia
    • A blood transfusion or organ transplant before 1992
    • Healthcare needlestick injuries
    • Being born to a mother with hepatitis C
    • HIV co-infection
  • How does hepatitis C cause liver damage?

    Hepatitis C mainly causes damage by triggering inflammation in the liver, which over time leads to fibrosis (scarring). As the scarring progresses, the liver gradually loses its ability to filter blood, resulting in compensated cirrhosis (in which the liver is damaged but remains partially functional) and eventually decompensated cirrhosis (in which the liver no longer works).

  • What is the risk of liver cancer from hepatitis C?

    If left untreated, chronic hepatitis C infection is associated with anywhere from a 1% to 7% risk of developing liver cancer. The risk increases in tandem with the severity of fibrosis. People with mild fibrosis rarely develop cancer.

  • Can you get hepatitis C more than once?

    Yes. There are seven major genotypes (genetic strains) of hepatitis C virus, and infection with one genotype does not confer immunity against the others. This is important given that some hepatitis C drugs can only treat certain HCV genotypes.

  • Can hepatitis C kill you?

    Yes, and it’s of growing global concern. Over 17,000 people in the United States die of hepatitis C-related complications each year, including liver failure and liver cancer. Around the world, over 700,000 deaths are attributed to hepatitis C annually.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Charles Daniel
 Charles Daniel, MPH, CHES is an infectious disease epidemiologist, specializing in hepatitis.