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| Andrew and granddad Rollosson |
Andrew received his first hepatitis B vaccine a few minutes
after he was born. As I prepared to write an entry on hepatitis B vaccine I
realized that this is a topic that I cannot adequately cover in a single post,
so I've decided to start by writing an overview on hepatitis. This will also
serve as a basis for my entry on hepatitis A vaccine when that time comes.
According to Steadman's
medical dictionary, the word hepatitis comes from the Greek words hepar, meaning liver, and the suffix -ites, which commonly refers to
inflammation or disease. The symptoms of hepatitis are caused by impairment of
normal liver functions; these include breaking down toxins, hormones, drugs,
and other substances, making clotting factors,
and making albumin,
a protein that holds water in the blood vessels. The liver also takes bilirubin,
a byproduct of the breakdown or red blood cells, out of the blood and uses it
to make bile,
which aids in the digestion of fats.
Early symptoms of acute hepatitis include
fatigue, malaise,
muscle and joint pain, nausea and vomiting, and pain over the liver. Jaundice is yellow
discoloration of the skin and sclera
(whites of the eyes) from deposition of bilirubin. While jaundice is the most
recognizable symptom of acute hepatitis, newborn jaundice is not caused by hepatitis.
There are many causes of hepatitis; both infectious and
non-infectious. Non-infectious hepatitis include alcoholic hepatitis, autoimmune hepatitis, drug-induced hepatitis, and ischemic hepatitis. Acetaminophen (Tylenol®) is a common cause of
drug-induced hepatitis. Many cold and allergy preparations contain
acetaminophen, so unintentional overdoses can occur when these medications are
combined.
-
Acetaminophen and children: Why dose matters
- Acetaminophen overdose
- Careful: Acetaminophen in pain relief medicines can cause liver damage
Aside from the hepatotropic viruses, several other viruses
can cause hepatitis including cytomegalovirus
(CMV), Epstein-Barr virus (EBV), herpes simplex virus (HSV), varicella-zoster virus (VZV), and yellow fever virus. Bacterial causes of hepatitis include brucellosis,
leptospirosis, Lyme disease,
and syphilis.
Hepatotropic viruses
Hepato, liver + -tropic, having an affinity for (Steadman's).
There are five known hepatotropic viruses that cause disease
in humans: hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus
(HCV), hepatitis D virus (HDV), and hepatitis E virus (HEV). There is another
hepatotropic virus, GB virus type C (formerly known as hepatitis G virus), but it is not known to
cause disease in humans. All five hepatotropic viruses can cause acute
hepatitis, but only HBV, HCV, and HDV can cause chronic hepatitis.
Like other viruses, hepatotropic viruses invade cells and
use the cells' protein synthesis mechanisms to make copies of themselves.
However, hepatotropic viruses do not damage the liver directly. Hepatocytes
("liver cells") infected with a hepatotropic virus are targeted and
killed by the immune system. In general, infants and young children are more
"tolerant" of infection with hepatotropic viruses and are therefore
more likely to have no symptoms or only mild symptoms of acute infection than
adults. Unfortunately, this also means that people infected with either
hepatitis B virus or hepatitis C virus as children, especially during infancy, are much more likely to be chronically
infected with those viruses than adults. Adults tend have more severe acute
symptoms but clear the infection more effectively than children.
Hepatitis A virus and hepatitis E virus are transmitted by the fecal-oral route. That means that to be infected with either HAV or HEV, something that a person eats, drinks, or otherwise puts in her or his mouth must be contaminated with feces. There are a lot of very common pathogens transmitted by the fecal-oral route. In two weeks, Andrew will have his first dose of rotavirus vaccine. Rotavirus, which causes diarrhea in infants, is transmitted by the fecal-oral route. Norovirus, which causes diarrhea and vomiting and is common called "stomach flu" (pet peeve: it's not the flu!), is also transmitted by the fecal-oral route. HAV, HEV, rotavirus, and norovirus are highly contagious, so it only takes a small inoculum (infecting dose) for a person to become infected and get sick with one of these viruses.
Hepatitis A used to be a very common childhood infection in
the U.S. (I had it when I was 6 years old). The incidence of hepatitis A has
dropped dramatically since the recommendation for universal childhood
immunization with hepatitis A vaccine (CDC, 2006).
There are sporadic outbreaks of hepatitis E in the U.S., but
it is much more common in developing countries. Like hepatitis A, HEV infection
is usually self-limiting, however, hepatitis E is much more severe in pregnant
women and is a significant cause of maternal death.
I had planned to write that there is no hepatitis E vaccine
until I saw the table of contents for the September 2012 issue of Emerging Infectious Diseases: Hepatitis E, a vaccine preventable cause of maternal deaths. The State Food and Drug
Administration of China approved a hepatitis E vaccine.
Hepatitis B virus, hepatitis C virus, and hepatitis D virus are transmitted by blood and bodily fluids. My next post will be on hepatitis B, so I'll go into more detail about transmission and epidemiology of these viruses as well as the effects of chronic hepatitis.
I'll end by quickly discussing a recent Centers for Disease
Control and Prevention (CDC) recommendation.
There are an estimated 2.7 to 3.9 million people in the United States infected
with hepatitis C virus, most of whom are unaware of their infection. In the
U.S., the majority of people infected with hepatitis C virus are between 45 and
65 years of age. The CDC therefore recommends that all persons born between
1945 and 1965 ("baby boomers") be tested for hepatitis C. People who
are infected with hepatitis C virus will be advised how to avoid progression to
cirrhosis of
the liver and hepatocellular carcinoma (liver cancer). There are also treatments available to prevent
progression to severe disease.
References:
Centers for Disease Control and Prevention. (2006).
Prevention of hepatitis A through active or passice immunization:
recommendations of the Advisory Committee on Immunization Practices (ACIP). Morbidity and Mortality Weekly Report,
55(7), 1-23. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5507a1.htm.
Centers for Disease Control and Prevention. (2012). Recommendations
for the identification of chronic hepatitis C virus infection among persons
born during 1945-1965. Morbidity and
Mortality Weekly Report, 61(4), http://www.cdc.gov/mmwr/preview/mmwrhtml/rr6104a1.htm.
Cohen, A. (2000). Liver disease. In L-E. C. Copstead &
J. L. Banasik (Eds.) Pathophysiology:
biological and behavioral perspectives (2nd ed.). Philadelphia: Saunders.
Curry, M. P. & Chopra, S. (2009). Acute viral hepatitis.
In G. L. Mandell, J. E. Bennett, & R. Dolin. (Eds.). Mandell, Douglas, and Bennett’s principles and practice of infectious
diseases. (7th Ed.). [Electronic version].
Dienstag, J. L. (2009). Chronic viral hepatitis. In G. L.
Mandell, J. E. Bennett, & R. Dolin. (Eds.). Mandell, Douglas, and Bennett’s principles and practice of infectious
diseases. (7th Ed.). [Electronic version].
Ferrante, M. A. (2003). Endogenous metabolic disorders. In
C. Goetz (Ed). (2003). Textbook of
clinical neurology (2nd ed.). Philadelphia: Saunders.
Labrique, A. B., Sikder, S. S., Krain, L. J., West, K. P.,
Christian, P, Rashid, M., et al. (2012). Hepatitis E, a vaccine-preventable
cause of maternal deaths. Emerging
Infectious Diseases, 18(9), http://wwwnc.cdc.gov/eid/article/18/9/12-0241_article.htm.
Mast, E. E. & Ward, J. W. (2008). Hepatitis B vaccine.
In S. A. Plotkin, W. A. Orenstein, & P. A. Offit (Eds.) Vaccines (5th Ed.) [Electronic version].
Ryder, S. D. (2010). Viral hepatitis. In J. Cohen, S. M.
Opal, & W. G. Powderly (Eds.) Infectious
diseases (3rd Ed.). [Electronic version].
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