Hepatitis C pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editor-In-Chief: Nina Axiotakis [2]
The Virus
The Hepatitis C virus (HCV) is a small (50 nm in size), enveloped, single-stranded, positive sense RNA virus in the families Flaviviridae.
Transmission
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The hepatitis C virus (HCV) is transmitted by blood-to-blood contact. In developed countries, it is estimated that 90% of persons with chronic HCV infection were infected through transfusion of unscreened blood or blood products or via injecting drug use or by inhalational drug use. In developing countries, the primary sources of HCV infection are unsterilized injection equipment and infusion of inadequately screened blood and blood products.
Although injection drug use and receipt of infected blood/blood products are the most common routes of HCV infection, any practice, activity, or situation that involves blood-to-blood exposure can potentially be a source of HCV infection. The virus may be sexually transmitted, although this is rare, and usually only occurs when a second STD makes blood contact more likely.[1]
Methods of transmission
Several activities and practices have been identified as potential sources of exposure to the hepatitis C virus. Anyone who may have been exposed to HCV through one or more of these routes should be screened for hepatitis C.
- Injection drug use
Those who currently or have used drug injection as their delivery route for illicit drugs are at increased risk for getting hepatitis C because they may be sharing needles or other drug paraphernalia (includes cookers, cotton, spoons, water, etc.), which may be contaminated with HCV-infected blood. An estimated 60% to 80% of all IV drug users in the United States have been infected with HCV. Harm reduction strategies are encouraged in many countries to reduce the spread of hepatitis C, through education, provision of clean needles and syringes, and safer injecting techniques.
- Drug use by nasal inhalation (Drugs which are "snorted")
Researchers have suggested that the transmission of HCV may be possible through the nasal inhalation (insuffulation) of illegal drugs such as cocaine and crystal methamphetamine when straws (containing even trace amounts of mucus and blood) are shared among users.[2]
- Blood products
Blood transfusion, blood products, or organ transplantation prior to implementation of HCV screening (in the U.S., this would refer to procedures prior to 1992) is a decreasing risk factor for hepatitis C.
The virus was first isolated in 1989 and reliable tests to screen for the virus were not available until 1992. Therefore, those who received blood or blood products prior to the implementation of screening the blood supply for HCV may have been exposed to the virus. Blood products include clotting factors (taken by hemophiliacs), immunoglobulin, Rhogam, platelets, and plasma. In 2001, the Centers for Disease Control and Prevention reported that the risk of HCV infection from a unit of transfused blood in the United States is less than one per million transfused units.
- Iatrogenic; medical or dental exposure
People can be exposed to HCV via inadequately or improperly sterilized medical or dental equipment. Equipment that may harbor contaminated blood if improperly sterilized includes needles or syringes, hemodialysis equipment, oral hygiene instruments, and jet air guns, etc. Scrupulous use of appropriate sterilization techniques and proper disposal of used equipment can reduce the risk of iatrogenic exposure to HCV to virtually zero.
- Occupational exposure to blood
Medical and dental personnel, first responders (e.g., firefighters, paramedics, emergency medical technicians, law enforcement officers), and military combat personnel can be exposed to HCV through accidental exposure to blood through accidental needlesticks or blood spatter to the eyes or open wounds. Universal precautions to protect against such accidental exposures significantly reduce the risk of exposure to HCV.
- Recreational exposure to blood
Contact sports and other activities, such as "slam dancing" that may result in accidental blood-to-blood exposure are potential sources of exposure to HCV.
- Sexual exposure to blood
Sexual transmission of HCV is considered to be rare. The CDC does not recommend the use of condoms between discordant couples (where one partner is positive and the other is negative); however, because of the high prevalence of hepatitis C, this small risk may translate into a non-trivial number of cases transmitted by sexual routes. Vaginal penetrative sex is believed to have a lower risk of transmission than sexual practices that involve higher levels of trauma to anogenital mucosa (anal penetrative sex, fisting, use of sex toys).[3]
- Body piercings and tattoos
Tattooing dyes, ink pots, stylets and piercing implements can transmit HCV-infected blood from one person to another if proper sterilization techniques are not followed. Tattoos or piercings performed before the mid 1980s, "underground," or non-professionally are of particular concern since sterile techniques in such settings may have been or be insufficient to prevent disease.
- Shared personal care items
Personal care items such as razors, toothbrushes, cuticle scissors, and other manicuring or pedicuring equipment can easily be contaminated with blood. Sharing such items can potentially lead to exposure to HCV.
HCV is not spread through casual contact such as hugging, kissing, or sharing eating or cooking utensils.
Vertical transmission
Vertical transmission refers to the transmission of a communicable disease from an infected mother to her child during the birth process. Mother-to-child transmission of hepatitis C has been well described, but occurs relatively infrequently. Transmission occurs only among women who are HCV RNA positive at the time of delivery; the risk of transmission in this setting is approximately 6 out of 100. Among women who are both HCV and HIV positive at the time of delivery, the risk of HCV is increased to approximately 25 out of 100.
The risk of vertical transmission of HCV does not appear to be associated with method of delivery or breast feeding.
Co-infection with HIV
Approximately 350,000, or 35% of patients in the USA infected with HIV are also infected with the hepatitis C virus, mainly because both viruses are blood-borne and present in similar populations. In other countries co-infection is less common, and this is possibly related to differing drug policies. HCV is the leading cause of chronic liver disease in the USA. It has been demonstrated in clinical studies that HIV infection causes a more rapid progression of chronic hepatitis C to cirrhosis and liver failure. This is not to say treatment is not an option for those living with co-infection.
References
- ↑ What is hepatitis?, Planned Parenthood, accessed May 15, 2007
- ↑ Thompson S, Hernberger F, Wale E, Crofts N (1996). "Hepatitis C transmission through tattooing: a case report". Aust N Z J Public Health. 20 (3): 317–8. PMID 8768424.
- ↑ Hahn JA (2007). "Sex, Drugs, and Hepatitis C Virus". J Infect Dis. 195: 1556&ndash, 9.