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Hepatitis A (HAV) (Serological Time Course (IgM (Peak at week 6 after peak…
Hepatitis A (HAV)
Clinical Features
Symptoms by age
<6yrs
More likely to be asymptomatic
14yrs
More likely to be symptomatic
All age groups are likely to recover
Incubation period
30 days average
15-50 days range
Rare complications
Fulminant hepatitis
Relapsing hepatitis
No chronic sequelae
Serological Time Course
Peak Viremia
From week 1-6
Decreases when immune response kicks in
IgM
HAV in Stool
Peak is of a similar time to viremia peak
Also decreases with IgM increase
IgM
Peak at week 6 after peak ALT in blood
Still have clinical symptoms
Coincides with ALT decreasse therefore HAV immune mediated
IgG
Specific
Coincides with IgM decrease obvs
Liver function
Peak elevation of ALT in blood at week 4
Coincides with period of
clinical illness
Alanine transferase liver enzyme looked at
Transmission
Mainly Faecal Oral
Some serum transmission
Places with...
Very Low Endimicity
Mostly adults
Travellers not been vaccinated
Not common outbreaks
Low disease rate
High
Early childhood
Low-High disease rate
Person to person transmission
Outbreaks uncommon
Moderate
Waterbourne and food outbreaks
Pathogenicity
Replicates in liver hepatocytes
Exits in bile
Hepatic damage mostly immune-mediated
As Virus not that pathogenic in experiments
NK and CD8+ T-cells kill infected hepatocytes
Maximal virus shedding in faecal before liver pathology
Vaccination
Single worldwide serotype world-wide
Formalin-inactivated vaccine
USA
Highest prevalence in Hispanic and Native American ethnic groups
Not socioeconomic, most contact with infected individuals
West to east pattern of H-L prevalence
Person to person
Initially high risk groups were vaccinated
Slight decrese
Then children
Large decrease in cases
Then all children
Most cases of symptomatic disease in adults
These were from children
Makes sense to vaccinate children
UK
Got a decrease in cases at same time as USA (1990-2003)
No HAV vaccination program
Decrease due to improved water quality in rivers and coast
10 fold reduction
Control
Improve sanitation
Picornavirus
Epidemiology
Expected as main transmission is
faecal-oral
Also less developed countries
Highly Endemic in South Africa