Hepatitis Flashcards
hepatitis A mode of transmission
fecal-oral
hepatitis A virus classification
picornavirus - negative sense ssRNA
why is overt disease rare for hep A?
it is common where sanitation is poor b/c mothers have immunity to it. this gives their kids passive immunity to it. most kids are exposed early in live, when they have partial immunity that gives rise to active immunity. most people are seroconverted by 5.
in developed countries, the infected individuals are older
how long is the incubation period for hep A
30 days
fecal excretion occurs after a few days
viremia takes a week
what cells do hepatitis A viruses infect?
liver
what are the symptoms of hep A infection?
anorexia, nausea, fever, jaundice, dark urine, and abnormal values from liver function tests
liver function tests
used to test for the presence of liver damage.
most common- aspartate amino transferase in the serum. this enzyme is normally in the liver but the virus lysis cells when it replicates to release progeny
describe how heme metabolism is related to hepatitis A
normally, heme is converted to bilirubin in the spleen, which is transferred through the blod to the liver, where it is added to the bile and excreted to the GI tract (its why feces are brown)
w/ Hep A, the liver functions poorly, causing an increase in bilirubin systemically. this gets deposited in the skin (causing jaundice), filtered by the kidneys (dark urine), and it doesn’t get to the GI tract (light feces).
compare AST levels in Hep A and Hep B
Hep A levels have a sharp peak w/in 2 months of infection, and then drop off sharply
in Heb B, the peak is slower to form and lower. it only becomes evident at 2 months
what are 5 most common ways to produce a Hep A epidemic
- outdoor summer events w/ inadequate sanitary facilities
2 raw or inadequately cooked shellfish contaminated by sewage
3 w/in one family
4 spread by food handler
5 from fecally contaminated food
T/F- Hep A can be spread via blood transfers
T- as long as the virus is viremic
describe the use of passive immunity from IgG in Hep A
primarily used after possible exposure, but still useful prophylactically.
it prevents jaundice and malaise, but there is some virus replication and liver damage.
it provides protection for about 4 months
describe Hep A immunization
killed virus vaccine. recommended for all children plus travelers, male gay partners, ppl who receive blood products
how do you determine if you are affected w/ hep A
serological test for Ab against Hep A
how do you interpret serological data w/ IgM and IgG for Hep A?
if both negative- no infection, no vaccine
if IgG pos- previously infected or vaccinated, but not currently
both pos- acute Hep A infection or recent vaccination
what dimensions are important to assess when considering a potential epidemic?
1 place- geographical clustering
2 person- do patterns suggest a mode of exposure
3 are new cases around the same time?
Hepatitis E characteristics
non-enveloped, + stranded RNA
what is the mode of transmission for Hep E viruses?
fecal-oral
what are the symptoms of Hep E?
similar to A
fever, nausea, jaundice
what is the Hep E prognosis
people generally recover. children often have very mild symptoms.
can become chronic in immunosuppressed pts
bad for pregnant women
what kind of virus is Hep B
hepadenavirus
enveloped, icosahedral
contains circular DNA mostly double stranded but single stranded some places
it carries a reverse transcriptase
what is the incubation period for Hep B
70 days
how is hep B transmitted?
blood transfusions, dirty needles
sexually (especially male to male)
perinatal infections from infected mom to newborn
are HB-Ags from the envelope or the capsid?
both
