HOW HBV IS TRANSMITTED?
Approximately one third of the world’s population or about 2 billion people, have been exposed to, or are currently infected with, HBV. Approximately 200,000 new HBV infections occur annually in the United States. How did all these people acquire this virus? Well, HBV is an extremely hardy virus. It has been detected in blood, sweat, tears, saliva, semen, vaginal secretions, menstrual blood, and breast milk. However, only blood, semen and (possibly) saliva have been found to be modes for transmitting the infection. HBV is much harder to catch than the virus that causes a cold or the flu, but a lot easier to catch than HIV (the virus that causes AIDS), or HCV (the virus that causes hepatitis C).
As discussed in Chapter 7, HBV is transmitted to others parenterally (introduced into the body by any way other than via the intestinal tract). Hepatitis B is not transmitted by the casual contacts which occur in the course of daily life. Thus, a person cannot get hepatitis B from eating food prepared by an infected person, by shaking hands with or hugging an infected person, or by visiting an infected person. Rather, HBV is transmitted in three different ways: through blood or blood products, through sexual contact, or from mother to child during pregnancy and childbirth. In areas of low endemicity, such as the United States, hepatitis B is usually transmitted through sex or intravenous drug use. In areas of high endemicity, such as Africa, Asia, and the Alaska, Hepatitis B is usually transmitted at childbirth from the infected mother.
Only a small percentage of adults in the United States harbor infectious hepatitis B viral particles that can be transmitted to others. If a person has hepatitis B, it does not mean that they are automatically infectious to others. See page xx to find out how a person can determine if she is infectious. The following is a discussion of how HBV is transmitted.
Blood or Blood Products
Prior to 1975, many people developed hepatitis B after having received contaminated blood or blood products, such as fresh frozen plasma (FFP) or platelets, during a transfusion. Since 1975, the blood supply in the United States has been carefully screened for HBV. Consequently, few people nowadays contract hepatitis B through a blood transfusion. Still, there are a lot of other ways a person can come into contact with infected blood, such as through the sharing of toothbrushes, razors, or nail clippers—each of which can carry and transmit infectious hepatitis B viral particles. Therefore, people who have someone with infectious hepatitis B in their household need to take special precautions. People with infectious hepatitis B who have skin conditions that can bleed -such as psoriasis or dermatitis, should take special precaution to cover open lesions or wounds. This is also sound advice for anyone with infectious hepatitis B who has open bleeding cuts or wounds due to any cause.
Intravenous drug users by sharing needles even on one occasion, can transmit the virus among themselves. If not sterilized properly, needles used for tattooing, ear-piercing, body -piercing, and acupuncture may be tainted with flecks of infected blood. Thus, these practices may be said to involve some risk of transmitting HBV. Even barbers and manicurists can transmit the virus if their equipment is contaminated with infected blood. Straws, dollar bills, or other instruments shared when “snorting” drugs- such as cocaine, can transmit small amounts of HBV infected blood from broken blood vessels in the nose from one person to another. And since being accidentally stuck with a needle or other sharp instrument is an occupational hazard of the medical and dental professions, health-care workers are particularly at risk for infection with hepatitis B.
Other people at risk include those with kidney failure undergoing hemodialysis—a procedure that helps filter blood, or those receiving a transplanted organ infected with HBV. It should be noted that HBV can remain infectious on a surface for up to one week. Thus, although unlikely, it is theoreticallly possible to acquire HBV unknowingly from an inanimate object.
Sexual Contact
HBV is 100 times easier to transmit sexually than HIV ( the virus that causes AIDS). HBV has been found in vaginal secretions, saliva, and semen. Therefore, it doesn’t matter if a person’s sexual partner is of the same or the opposite gender. If one partner has hepatitis B, the other one can get it. Oral sex and especially anal sex regardless (whether it occurs in a heterosexual or homosexual context), are possible ways of transmitting the virus. It is not transmitted by holding hands, hugging or even dry kissing on the lips. The chance of transmission with deep kissing is unknown, as no infections have been definitively documented after exposure to infected saliva. Yet, since HBV has been found in saliva, the risk of transmission with deep kissing probably exists and the risk increases if one partner wears orthodontic braces or has open cuts or sores in the mouth. The likelihood of becoming infected with HBV grows with the number of sexual partners a person has. Thus, promiscuous individuals are more likely to get HBV. Also, men who have sex with men are 10-15 times more likely to catch HBV than the general population.
Childbirth
An infected mother can transmit HBV to her child during childbirth. This mode of transmission is known as perinatal transmission. It accounts for the high rates of infection in Asian and African countries, as asymptomatic mothers, unaware that they carry infectious hepatitis B, transmit it to their newborn infants at childbirth.
In the United States, all pregnant women are screened for the presence of HBV, and all babies born to infected mothers immediately receive immunization. In fact, in the United States, it is now common practice to vaccinate infants against hepatitis B, regardless of the mother’s HBV status. As a result, there is hope that this infection will, in time, become a disease of the past. For more information on vaccinations, see Chapter 24. New mothers are also advised to avoid breast-feeding if they are infectious, even though this mode of transmission has not been considered very significant. Of course, if the mother has bleeding nipples the risk of transmitting HBV increases.