Hepatitis C infection is estimated to be responsible for most chronic liver disease in the United States and 8,000 to 10,000 deaths annually.
Acquisition of hepatitis C infection is very rapid among new drug injectors with 50 to 80 percent infected within 6 to 12 months.
Research has shown that hepatitis C infection is widespread in populations of experienced drug injectors, with rates in many areas of the United States exceeding 80 percent.
Hepatitis C is the most common chronic blood-borne infection in the United States. Approximately 4 million Americans have been infected with the hepatitis C virus (HCV). And epidemiologic studies show that HCV is now endemic among injection drug users (IDUs), the result of risk behaviors such as sharing of syringes and other paraphernalia. In fact, over the past decade injection drug use has become the major mode of HCV transmission in the United States, accounting for at least 60 percent of transmitted cases. Thus, HCV is a serious medical consequence of drug abuse that needs to be considered when providing care to drug abusers.
This Community Drug Alert Bulletin summarizes the latest scientific information on HCV, particularly for health care providers working with patients who may be at increased risk of infection because of current or past injection drug use.
Counseling and education by health care professionals to prevent initiation of injection drug use and high-risk sexual practices is important, especially for adolescent and young adult populations. Adolescents and young adults, particularly those who use drugs, are critical targets for prevention efforts, since the highest rate of new HCV infection is found among people aged 20 to 39.
Current IDUs and other individuals who have injected drugs, even once in the remote past, should be tested for HCV, as should HIV-infected individuals. Also, anyone who received transfusions of blood or blood products before 1992 should be tested.
To date, there is no vaccine to prevent HCV infection, and treatments for chronic hepatitis C have been effective only in some individuals. The antiviral drug interferon, alone or combined with ribavirin, is approved for treatment of chronic hepatitis C. Researchers are working to develop more effective prevention and treatment approaches for this disease. It is important that people diagnosed with HCV infection undergo clinical assessment and monitoring for the presence of chronic liver disease. They should also be advised to reduce their alcohol use. Those who are substance abusers should be referred to drug abuse treatment programs.
Only a comprehensive approach and intensive research efforts will enable us to combat the public health problem that HCV poses. This bulletin will provide you with a snapshot of the most current information on this topic. We hope it will be useful to you as you care for your patients.
Alan I. Leshner, Ph.D.
What is Hepatitis C?
- Hepatitis C infection is caused by the hepatitis C virus, also known as HCV, a virus that infects cells in the liver.
- HCV is one of several viruses (hepatitis A, hepatitis B) that can cause an inflammation of the liver.
- Chronic infection with HCV can result in cirrhosis (liver scarring) or primary liver cancer (hepatocellular carcinoma).
Hepatitis C Infection
- Is prevalent in many countries worldwide.
- Is the most common chronic blood-borne infection in the United States, infecting an estimated 4 million Americans.
- Is transmitted primarily through direct exposure to infected blood.
- Is linked to injection drug use, which accounts for most HCV transmission in the United States.
- Is estimated to be responsible for most chronic liver disease in the United States and 8,000 to 10,000 deaths annually.
- Is the single most common reason for liver transplants in the United States.
- The highest rates of new infection are among persons 20 to 39 years old and the highest rates of chronic infection are among persons 30 to 49 years old.
Transmission of Hepatitis C Virus
- Sharing contaminated needles is the most common route of infection. Injection drug use is responsible for at least 60 percent of HCV infection in the United States.
- The risk of sexual transmission of HCV is much lower than the risk associated with contaminated needles, but still present. Sexual transmission is estimated to account for less than 20 percent of HCV transmission. The highest rates of sexual transmission are associated with multiple sex partners, and the increased risk may be associated with traumatic sex that results in blood exposure. Long-term monogamous sexual partners of persons infected with HCV have very low rates of becoming infected (0 to 4 percent).
- Prior to the discovery of the virus and the development of a screening test for blood, many people were infected through contaminated blood transfusions. Since 1992, infection from blood transfusions is rare in the United States.
- The average rate of transmission from an infected pregnant mother to her infant is 5 to 6 percent (range 0 to 25 percent). This risk increases if the mother is infected with both HCV and HIV, with reported transmission rates of 5 to 36 percent.
- Other potential risks for transmission include sharing contaminated straws during intranasal use of cocaine, and sharing items such as razors and toothbrushes, which may be contaminated with infected blood. Data on exposure risks from tattooing or piercing in the United States are sparse.
Injection Drug Use and Hepatitis C Infection
Although new infections among injection drug users in the United States have declined since 1989, both the incidence and prevalence of infection remain high. Studies have shown that infection is widespread in populations of experienced injectors, with rates in many areas of the United States exceeding 80 percent. Acquisition of hepatitis C infection is very rapid among new injectors following initiation of injection, with 50 to 80 percent infected within 6 to 12 months.
Risks for infection include needle sharing, frequent daily injection, cocaine injection, and sharing needles with a long-term injector. Because of the efficiency of blood-to-blood transmission and the high prevalence of infection among injectors, anyone who has ever injected drugs, even if he or she may have experimented only once in the past, is at risk for infection. Due to common modes of transmission, a large proportion of injection drug users infected with HCV are also infected with hepatitis B virus and/or HIV.
Natural History of the Illness
Following exposure to the virus, most people with acute infection display no symptoms and continue to feel well. However, some develop jaundice, and some people experience nonspecific symptoms such as anorexia (lack of appetite), malaise, and/or abdominal pain. Because specific symptoms are uncommon, the only way to determine whether infection is present is with a blood test for antibodies to the virus. The average incubation period for the virus is 6 to 7 weeks and antibodies to HCV can be detected in 80 percent of those infected by 15 weeks after exposure.
A small proportion of those with acute infection are able to clear the virus naturally from the bloodstream. However, 75 to 85 percent of those infected develop chronic infection. While most people with chronic infection do not have any symptoms, complications can occur after 10 to 20 years of unapparent infection. As liver cells die, scar tissue forms in the liver (fibrosis), preventing normal blood flow. This leads to a condition called cirrhosis, which can be life-threatening. It is estimated that cirrhosis occurs in 10 to 20 percent of people with chronic infection, and 1 to 5 percent develop primary liver cancer (hepatocellular carcinoma).
It is not yet known why some people are able to clear the virus, why disease severity varies from person to person, or how to predict who will develop disease. Unlike HIV, the amount of virus in a person's blood is not a good predictor of disease progression. Recent data show that alcohol consumption can increase the risk of progression, and studies indicate that persons infected with both HCV and HIV tend to have a more rapid decline in health.
While some antiviral treatment is available for HCV, it has not been found to be highly effective. It also has been shown to have toxic effects, and is often poorly tolerated. Research efforts to develop more effective treatment approaches that are appropriate for broader patient populations are ongoing. At present, the antiviral drug interferon, used alone or in combination with ribavirin, is approved for treatment of HCV. When interferon is combined with ribavirin, the effectiveness of treatment is improved. Studies indicate that the combination is effective in 30 to 40 percent of those treated, but that many patients relapse when therapy is stopped. Currently, treatment is recommended only for patients at greatest risk for progression to cirrhosis. Individuals found to be infected with HCV need to be assessed and monitored by a specialist for the presence and severity of chronic liver disease and for treatment eligibility. Infected persons should be advised to reduce alcohol intake and to abstain from using illicit drugs. Those using illicit drugs should be referred to drug treatment programs.
Screening and Prevention
Unlike hepatitis A and hepatitis B, there is no vaccine to prevent hepatitis C infection. Thus, prevention efforts must rely on behavioral techniques.
Persons who have injected illicit drugs, including those who injected only once or occasionally many years ago and who may not consider themselves to be drug users, should be tested for hepatitis C infection. Because of similar risk factors for infection, drug users should also be tested for HIV and hepatitis B. Those at risk should receive immunization for hepatitis A and B. Persons with known HIV infection should be screened for HCV as well.
Regardless of test results, persons who use illicit drugs should be counseled to reduce their risk for acquiring infection or of potentially transmitting infection to others. Persons with multiple sex partners should be advised to use latex condoms.
Persons who test positive for HCV should be given information regarding the need for preventing further harm to the liver, reducing risks for transmitting HCV to others, and obtaining medical evaluation and followup for chronic liver disease and possible treatment. It is important that physicians know if a person is infected with HCV so that medications that may have side effects involving the liver can be avoided. To protect the liver from further harm, HCV-infected persons should be vaccinated against hepatitis A and B, if susceptible, and should be strongly advised that even moderate alcohol consumption may adversely affect disease progression. All persons should be advised not to use illicit drugs.
Management of hepatitis C.; NIH Consensus Statement Online, March 24-26. 15(3): 1-41, 1997.
Recommendations for prevention and control of hepatitis C virus (HCV) infection and HCV-related chronic disease. Morbidity and Mortality Weekly Report 47 (RR-19), October 16, 1998.
NIDA Community Alert Bulletin on Hepatitis C was published in May, 2000