HOW HCV IS TRANSMITTED?
Most people are surprised to learn they have hepatitis C. Many people believe they were never at risk for acquiring this virus. They, therefore, cannot imagine how they contracted it. Other people have a definable risk factor, such as a history of intravenous drug use, but feel that it occurred such a long time ago that it has no relevance. And some people know exactly how they contracted it.
There are, in fact, many ways that a person can contract HCV. The most efficient mode of transmission is via blood-to-blood contact. This means that blood from an infected person gets into the bloodstream of another person. HCV can only enter the bloodstream by first getting through the protective covering of one’s skin. This is known as the percutaneous route. Read on for more information about all routes of transmission.
Blood and Blood Product Transfusions
It has been estimated by the Centers for Disease Control (CDC) that prior to 1990, when screening donated blood and blood products for HCV was begun, almost 300,000 Americans contracted HCV from transfused blood. This occurred as a result of receiving HCV-infected blood—packed red blood cells (PRBC) or blood products, such as platelets, fresh frozen plasma (FFP), or immune globulin. In addition, it has been estimated that almost 1 percent of all potential blood donors are infected with HCV. Fortunately, blood banks have been screening all potential donors for HCV since 1990. And since 1992, these screening techniques have been exceptionally accurate.
Today, the incidence of obtaining this virus by receiving a blood transfusion is approximately 1 in 125,000 to 1 in 200,000 per unit of blood transfused (the risk of infection is approximately 0.001 percent per unit of blood transfused). In essence, since 1992, the likelihood of contracting HCV from a blood transfusion has been minuscule. The reason that a small risk still exists is that when a person initially becomes infected with HCV, there is a short period of time, known as the window period, in which the HCV antibody (HCV Ab) is not detectable in the blood. If a person donates blood during the window period, her blood will carry HCV, but it will not be detectable. It is recommended that anyone who received a blood transfusion prior to 1992 be tested for HCV. Please note: Once somebody has tested positive for HCV, she should refrain from donating blood or organs.
Intravenous Drug Use
Intravenous drug use (IVDU) is the most common way of transmitting HCV, and it accounts for almost 70 percent of all new HCV infections. HCV has been found in approximately 85 to 100 percent of IV drug users. The longer a person uses IV drugs, the greater the likelihood one has of becoming infected with HCV. HCV is transmitted from one person to another through the sharing of needles and/or other drug paraphernalia. Even a speck of blood so small that it is undetectable to the human eye can carry a great deal of hepatitis C viral particles. Therefore, drug paraphernalia that appears to have been adequately cleaned may still contain HCV.
The decades of the 1960s and 1970s were characterized by considerable experimentation and rebellion. Intravenous drug use was sometimes a part of the culture that prevailed during this era. Though many users were aware that IV drug use was illegal, they were not aware that it had the potential to introduce a serious viral infection (one that had not even been identified) into their livers. For some, IV drug use was a daily occurrence. Others may have tried it only once or twice. But even a one-time occurrence long ago still may have relevance. Remember, HCV can reside in the body for many years, silently doing damage to the liver even though the person feels fine.
Intranasal Drug Use
Intranasal drug use, or “snorting” drugs, is also a potential route of virus transmission. Small blood vessels in the nose may break open and bleed when an instrument such as a straw or a rolled-up dollar bill is used to snort a drug, such as cocaine. Most of the time, the amount of blood on the instrument is so small that it is undetectable. When these instruments are shared, HCV can pass from one person to another. Once again, engaging in this activity even once may be sufficient to infect a person with HCV.
Health-Care and Occupational Exposure
Anyone who works in a health-care facility, including a hospital, doctor’s office, dentist’s office, or in a laboratory that handles blood specimens, is at risk of contracting HCV. Public safety workers, such as firemen, police officers and correction officers, as well as emergency medical technicians, may be exposed to blood due to the nature of their jobs and, therefore, are also at risk for becoming infected with HCV. The virus may be transmitted through a needle stick injury, a blood spill, or through pricking oneself with a contaminated sharp instrument. The larger the amount of contaminated blood that enters a person’s body, the higher the likelihood she will become infected. After a single incident of accidental exposure to HCV, the risk of contracting HCV is approximately 2 percent—although this probability has been reported to range between 0 and 16 percent. For comparison, the probability of contracting HBV by this route is 15 to 30 percent and for contracting HIV it is 0.3 percent. Even with the potential risk to health-care workers due to the nature of their profession, the prevalence of HCV infection among this group of professionals is actually about the same as that of the general population, which is 1 to 2 percent.
Occupational Exposure
People who work in a hospital or other health-care facility ( i.e. doctor’s office, medical labs, blood-bank), as well as public-safety and emergency medical workers, are at risk for contracting HCV while on the job, through a needle-stick or mucosal exposure ( exposure to the mucus-secreting membranes that lines a body cavity and communicates with the exterior- such as the inside of the mouth, nose, lips, and/or vagina) to the blood of an infected person. There is an approximately 2 percent chance of becoming infected with HCV after exposure to the blood of an HCV- positive person. However, the likelihood of contracting HCV ranges between 0- 10 percent, based on a variety of factors. First, the higher the person’s HCV viral load at the time of the incident, the higher the risk of acquiring the virus. HCV viral loads ( HCVRNA) greater than 500,000 IU/ml increase the likelihood of transmission. Second, the type of body tissue exposure influences the likelihood of transmission. The chance of transmission increases with exposure to mucous membranes, such as an eye splash (blood splashing into someone’s eye), and is the highest if there was exposure to breaks in the skin- such as an open wound or sore. HCV-infected blood on someone’s intact skin has never been reported as a cause of HCV infection. Third, the longer HCV is outside of the infected person’s body, the less chance there is of acquiring the virus. For example, HCV- infected blood from a test tube, or lying on a surface is less infectious than HCV infected blood coming directly from a person’s body. This is because the level of HCV infectivity (the level of HCV RNA in blood) declines once it is outside the infected person. Finally, the type of instrument that a person was stuck with is relevant to the likelihood of acquiring HCV. For example, sticking oneself with a solid needle (such as a suture needle) carries a relatively low chance of HCV acquisition since these needles can hold only a small volume of blood. In contrast, sticking oneself with a hollow-bore needle (such as a needle used in drawing blood) which can hold a large volume of HCV-infected blood, carries a higher risk of HCV acquisition.
The appropriate testing to obtain after an exposure, as well as possible treatment options after exposure, are discussed in my book.
Medical Procedures
The World Health Organization (WHO) estimates that approximately 2.3-4.7 million cases of HCV occur each year in developing countries as a result of the use of non-sterile, reused needles. The best known large-scale transmission of HCV from the health-care workers to patients occurred in Egypt, where approximately 7-15 million people became infected with HCV due to the reuse of nonsterile needles during a campaign to mass immunize the population for schistosomiasis (a parasite (worm) that may cause severe disease). In the United States, unsterile medical practices, such as reusing needles, have occurred in the past. This may partly explain the presence of chronic hepatitis C in older individuals in the United States who have no other definable risk factor. Many people who received vaccinations, particularly those in the military, prior to the widespread use of disposable needles acquired the virus by this means. Medical knowledge of appropriate sterility practices has advanced considerably over the past several decades in developed countries such as the United States. As such, transmission of HCV from health-care workers to patients accounts for less than 0.5 percent of HCV cases. The following is a discussion of the possible ways a health–care worker or a medical procedure may cause the transmission of HCV to an individual.
People with kidney failure who are undergoing hemodialysis have an increased risk of acquiring HCV. Hemodialysis is a medical procedure that involves removing the blood through an artery, cleaning it, and then returning it to the person through her vein. In fact, it is estimated that in the United States, approximately 20 to 30 percent of hemodialysis patients are infected with HCV. This is due to a combination of receiving frequent blood transfusions prior to 1992, possible inadequate sterilization of equipment used during the hemodialysis procedure, and the possible sharing of supplies among patients. Fortunately, the incidence of chronic hepatitis C in this group of people is decreasing due to the use of universal precautions in dialysis units and to improved methods of screening transfused blood.
Another medical procedure that puts one at risk of contracting HCV is undergoing an organ transplant. One may become infected with HCV by receiving an organ (such as a kidney, eye, heart, or even a liver) from a person infected with HCV. If an organ donor is infected with HCV, there is approximately a 50-percent chance that she will transmit the virus to the transplant recipient. Since there is a shortage of liver donors, some transplant centers will utilize the liver of a hepatitis C positive organ donor for transplant to a person with hepatitis C in need of a new liver. Unfortunately, prior infection with HCV will not protect the transplant recipient from developing another HCV infection with a different HCV genotype. (See page xx for a discussion of HCV genotypes.)
The medical practice of sharing multidose vials (vials containing more than one dose of medication) of, for example, local anesthetics, saline, heparin or other solutions, has been implicated in many small isolated outbreaks of HCV. Even minimal contamination of a medical product is sufficient to transmit HCV from one patient to the next via this indirect route.
Isolated instances of transmission during surgery, from surgeons infected with HCV to their patients have been noted. Though rare, it occurs primarily during cardiovascular thoracic surgery, as sharp edges of bone are encountered and metallic sutures are used, both of which can penetrate through sterile gloves causing bleeding during surgery.
The Centers for Disease Control does not recommend restricting the professional activities of HCV- infected health-care workers. As a practical matter, any restrictions should be evaluated on a case-by-case basis.
Tattooing and Body Piercing
Tattooing and body piercing, including piercing the ears, are practices that involve breaking the skin with a needle. In the course of these procedures, a small amount of bleeding can occur. If the needles, ink, or other equipment used during these practices are not sterile, HCV may be transmitted as one customer’s HCV-infected blood makes its way into the bloodstream of a subsequent customer.
Sexual Contact
Sexual contact, whether it be genital, oral, or anal, appears to be an extremely inefficient means of HCV transmission. In fact, many studies evaluating this mode of transmission have failed to detect the presence of HCV in either the saliva, semen, or urine of HCV-infected people—except when these body fluids have been contaminated by the person’s blood. However, it is important to emphasize that HCV has the potential to be transmitted through intimate contact if there is active bleeding -such as during menses (if the woman is infected with HCV), or if there are breaks in the skin or in the lining of the mouth, vagina, penis or anus. Breaks may occur for a variety of reasons including the presence of active, bleeding herpes sores or as a result of traumatic or rough sex, especially anal intercourse. In fact, it has been found that people with sexually transmitted diseases such as trichomonas, gonorrhea, as well as herpes, as well as men who have sex with men, are both factors that have been found to increase the likelihood of sexual transmission. Since HCV can be present in menstrual blood, extra precautions (the use of dental dams and condoms) should be considered during and just after menstruation to decrease the chance of transmission, particularly if the sexual partner has open cuts or wounds. Also, sanitary napkins or tampons should be placed in a leak-proof sealed bag and promptly disposed of. Finally, it has been found that people co-infected with both HIV and HCV may have an increased potential for transmitting HCV through sexual contact. Of interest is that it appears to be easier for a man to transmit HCV to a woman than vice versa.
Assuming the absence of the above factors, and assuming that blood is not exchanged during sex, a person who is in a long-term monogamous relationship with an HCV-infected person is not likely to contract the hepatitis virus from sexual relations with their partner. Therefore, barrier precautions are not routinely recommended for such people.
Some studies have tested the sexual partners of hepatitis C patients to see whether they too are HCV-positive. Such studies have produced results ranging from 0 percent to 6 percent positivity- with approximately 2 percent being the average. However, it is crucial to keep in mind that it is not known whether these sexual partners acquired the hepatitis C virus through sex or by another route.
Household Contact
Transmission of HCV among family members or among other people living together may occur. This can potentially happen through the sharing of razors, toothbrushes, or any sharp instruments that carry HCV-infected blood. Therefore, it is crucial to keep each person’s personal items, such as toothbrushes and razors, in separate areas of bathroom, and each item should be clearly labeled. In this manner, the likelihood of accidentally using a potentially HCV-infected household item will be decreased. In the United States, the incidence of contracting HCV from accidental household contact is unknown. However, data from other countries indicate that it is low—approximately 4 percent.
Childbirth
Of great concern to pregnant women infected with HCV and to women with chronic hepatitis C who are contemplating pregnancy is the likelihood of transmitting the virus to their babies. However, the risk for either of these types of transmission is very low—occurring only approximately 3 to 7 percent of the time. Transmission to the newborn has been found to occur only in HCV-infected women who had high viral loads (the amount of HCV viral particles per milliliter of blood) of at least 2 million. It has also been noted that women who are co-infected with HIV and HCV appear to have a higher probability of transmitting HCV to their newborns than women who are not infected with HIV. Please refer to chapter 24 page xx for more information on this topic.
Breast-feeding is not considered a means of transmitting HCV. Therefore, it is believed that an HCV-infected mother may safely breast-feed her child, unless nipples are cracked and bleeding. Studies comparing the incidence of HCV in breast-fed versus bottle-fed infants of mothers with HCV showed a fairly equal incidence of HCV in each group of infants—approximately 4 percent.
Other Routes of Transmission
Though the reasons are not entirely clear, some population groups, such as in certain parts of Africa, some portions of Italy, and some parts of Japan, have been found to have a particularly high incidence of hepatitis C. Some indigenous healing or folk-medicine practices common to these regions, involving skin piercing with unsterilized instruments, are suspected to account for the disproportionately high incidence of the virus. Reuse of nonsterile needles and syringes by health-care workers (as discussed above) is another likely reason for the unusually high incidence in some of these regions.
Another potential, yet unlikely, route of transmission involves insects. Theoretically, transmission by insects can only occur if an insect bites an HCV-infected person and then immediately bites someone else. In this way, the HCV-tainted blood could enter the second person. Viruses other than HCV, such as yellow fever and dengue, have been shown to spread by this route. One study conducted in New Jersey concluded that mosquitoes are unlikely agents of transmission of HCV. Therefore, while not believed to be a significant source of HCV transmission, further investigation into the area of insect transmission is needed.
In some societies, cults and fraternity members mix their blood together as part of a ritual or in order to be inaugurated. Sometimes, people will mix their blood with that of a close friend or partner in a process by which they become “blood brothers.” This potential mode of HCV transmission also warrants further investigation.
Finally, even a barber or a manicurist may be a risk factor. If the instruments they use are not properly cleaned, they can potentially carry a small amount of HCV. Similarly, people undergoing acupuncture or electrolysis are at risk of becoming infected with HCV if the needles and other equipment being used have not been properly sterilized.
Sporadic Hepatitis C
Some people who have hepatitis C state that they cannot identify a risk factor to account for their HCV infection. This group of people has been classified as having sporadic hepatitis C. Note, however, that some people who have sporadic hepatitis C probably do have an identifiable risk factor, but are concealing it for personal reasons. They may have fear a lack of confidentiality on the part of their doctors, they may fear of being judged as having done something bad ( or illegal) in the past, or they may fear being rejected for life or medical insurance. Others do not consider a certain behavior to count as a risk—behaviors such as having a body part pierced or an isolated occurrence of intravenous or intranasal drug use—and therefore deny it when questioned. In fact, in one study, many former IV drug users with hepatitis C who attempted to donate blood denied their IV drug use when screened at the time of blood donation, as they felt that their former habit was such an insignificant event that it would not affect the purity of their blood. Others feel that an episode that happened long ago doesn’t count anymore, and, therefore, they don’t disclose it to their doctors. Finally, some people simply do not recall the incident that caused the infection.
All contents of this article are Copyright © Melissa Palmer, MD
Melissa Palmer, MD is the author of " Dr. Melissa Palmer's Guide of Hepatitis and Liver Disease". (Published 2004. Penguin Putnam).
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