Blood Borne Hepatitis
Hepatitis B Virus
Hepatitis B virus (HBV), formerly called serum hepatitis, is much more prevalent than HIV (the virus that causes AIDS). An estimated 800,000 - 1.2 million Americans are affected by chronic HBV infection, with more than 300 million carriers worldwide. Only a fraction of all those are aware of their infection. Hepatitis B may develop into a chronic disease (lasting more than 6 months) in up to 10% of newly infected people each year.
Whereas healthy adults have a > 95% of resolving an acute infection, newborns or immune-compromised patients have a much higher degree of failure to clear the virus that then leads to chronicity: From birth the chance of > 90% risk of chronicity gradually drops until adulthood with the maturation of the immune system.
If left untreated, the risk of developing cirrhosis (scarring of the liver) and liver cancer is greatly increased.
This disease is much more infectious than HIV. It is transmitted through infected blood and other body fluids (seminal fluid, vaginal secretions, breast milk, tears, saliva and open sores). In the U.S., hepatitis B is spread predominantly through sexual contact. Other risk groups include health care workers, prison inmates and personnel, IV drug users, and recipients of blood transfusions prior to 1975. In families, it appears that the virus can be casually spread from adults to children.
The onset of hepatitis B may be as an acute obvious disease with jaundice (yellowing of the skin), or be associated with very mild and atypical symptoms. As with other forms of hepatitis, most people who get hepatitis B have no recognizable signs or symptoms. But some people do experience flu- like symptoms, such as loss of appetite, nausea and vomiting, fever, weakness, tiredness, as well as mild abdominal pain. Less common symptoms are dark urine. The lack of symptoms in acquiring the disease explains why many patients are much later diagnosed with the disease, unfortunately often when serious harm has been done.
The only way these diseases can be positively identified is through blood tests. Severe manifestations of chronic HBV infection include development of scarring of the liver (cirrhosis), and liver cancer which usually occurs decades later.
Someone suffers from chronic hepatitis B if the virus persists in his or her blood for more than six months. Such individuals may have no signs or symptoms of HBV but remain infected with the virus for years or for a lifetime and are capable of passing the disease on to others. Completely asymptomatic individuals, often called "carriers" remain at any time at risk for complications including significant flare-ups of the disease when treated for other conditions with immunosuppressive agents (prednisone, anti-cancer agents).
HBV infected patients need full evaluation to assess need for therapy and other measures.
Vaccines are widely available to prevent hepatitis B and are extremely effective. They exist also as a combination vaccine for HAV and HBV.
Hepatitis D Virus
Infection with hepatitis D (HDV, delta virus) occurs only in patients already infected with hepatitis B. The virus needs the replicative apparatus of the HBV virus in order to persist.
Hepatitis D is spread mainly by contaminated needles and blood. I.V. drug users have a high incidence. The simultaneous infection with HBV and HDV produces more severe illness, and higher rates of long term liver failure, than HBV alone. Patients with chronic HBV who subsequently are infected by HDV suffer much more severely compared to those who contract them at the same time.
Due to its co-dependence on HBV, hepatitis D is effectively prevented via the HBV vaccine.
Other Hepatitis Viruses
There is the strong assumption that other hepatitis viruses exist - in part due to the fact that the known viruses (A through E) do not explain all cases of hepatitis that are believed to be caused by viruses. Detailed studies are currently underway. However, the clinical significance and public health impact of other hepatitis viruses remains unknown.