Hepatitis A Flashcards
HAV classification & structure
Family: Picornaviridae
Genus: Heptaovirus
Structure: (+)ssRNA
four major polypeptides cleaved from a large precursor polyprotein. The surface proteins VP1 and VP3 are major antibody-binding sites. The internal protein VP4 is much smaller than the VP4s of other picornaviruses. As other picornaviruses, HAV has no envelope and replicates in the cytoplasm.
Baltimore class: IV
HAV maternal foetal transmission risk
Fulminant liver failure risk
0 - not described
<1%
HAV pathogenesis
Viral replication occurs in the hepatocyte cytoplasm; hepatocellular damage and destruction of infected hepatocytes is mediated by human leukocyte antigen-restricted, HAV-specific CD8+ T lymphocytes and natural killer cells [44-46]. Interferon-gamma appears to have a central role in promoting clearance of infected hepatocytes [44]. An excessive host response (denoted by a marked reduction of circulation HAV ribonucleic acid (RNA) during acute infection) is associated with severe hepatitis
HAV incubation & symptomatic rate
The incubation period of hepatitis A infection averages 28 days (range 15 to 50 days)
Symptomatic illness due to HAV occurs in more than 70 percent of adults. Symptoms are uncommon in children <6 years of age.
HAV infectious period
Infected individuals are contagious during the incubation period and remain so for about a week after jaundice appears [53].
HAV replicates in the liver and is shed in the stool in high concentrations from two to three weeks before to one week after onset of clinical illness
HAV outcomes
HAV infection does not become chronic, and individuals cannot become reinfected after recovering from infection. However, relapse can occur.
Relapsing hepatitis — Up to 10 percent of patients experience a relapse of symptoms during the six months after acute illness. The duration of clinical relapse is generally less than three weeks, although biochemical relapse may last as long as 12 months [67]. The cause of relapsing hepatitis is unknown, and no predisposing factors for relapse have been identified.
Serum aminotransferases may exceed 1000 international units/dL, and serum anti-HAV IgM antibodies typically persist throughout the course of the disease [63,68]. HAV can be recovered from stool during relapse episodes, so such patients should be considered infectious.
Multiple relapses can occur.
Mortality < 0.5%
HAV diagnostics
The diagnosis is established by detection of serum IgM anti-HAV antibodies. Serum IgM antibodies are detectable at the time of symptom onset, peak during the acute or early convalescent phase of the disease, and remain detectable for approximately three to six months (figure 2). Among patients with relapsing hepatitis, serum IgM antibodies persist for the duration of this disease
Serum IgG antibodies appear early in the convalescent phase of the disease, remain detectable for decades, and are associated with lifelong protective immunity.
HAV treatment
Supportive
Transplant
HAV PEP
SEE ALBUM
3 monovalent inactivated hepatitis A vaccines - all human diploid cell - HAVRIX, AVAXA and VAQTA. A combination inactivated vaccine, TWINRIX, contains both hepatitis A (HAVRIX) and hepatitis B (Engerix-B).
Regimen:
Monovalent - 0,6 months (extra dose for HIV CD4 less than 350).
Bivalent: 0,1,6 months
HNIG can decrease the incidence of HAV infection by more than 90 percent.
EXCLUDE index case from work for 7 days from jaundice/symptom onset.
PEP:
TESTING IS NOT A PREQUISITE. If testing, result should be available < 3 days & should be <10 days from exposure, and < 7 days from vaccine.
- IMMUNE - past HAV, 2 course vaccine in last 10 years, or 1 dose of vaccine in last 12 months
- SUSCEPTIBLE BUT PRIMED - 1 dose vaccine > 12 months ago, 2 doses > 10 years ago - ONLY VACCINE, no HNIG.
- SUSCEPTIBLE- no HAV or vaccine, IgG negative - GIVE HNIG UPTO 14 days from last exposure
First 14 days:
A. Healthy infants < 12 months - no PEP
B. 12 months to 59 years - single vaccine dose. 2nd dose at 6 months.
C. >60 years - HNIG + vaccine
D. CLD/HBV/HCV - HNIG + vaccine
E. Immunosuppressed/ HIV < 200 cells - HNIG + vaccine
F. Pregnant & breastfeeding - same as non-pregnant
After 14 days:
A. High risk of severe disease - consider HNIG upto 28 days and vaccinate
B. Food handlers - avoid touching uncooked food/food that will not be cooked again for 30 days. DOES NOT NEED EXCLUSION FROM WORK.
C. All other household - vaccine up to 8 weeks from exposure. (Age 2 months and up).
HAV case definition
Possible: clinical syndrome
Probable: clinical syndrome + epi link
Confirmed: clinical syndrome + IgM AND IgG or RNA
HAV SMI
SEE ALBUM
