Acute Viral Hepatitis Flashcards
General properties of viral hepatitis: virus, route of transmission, source, chronic infection or not, prevention methods, notifiable disease?
Acute hepatitis
- Hepatitis A and E virus
- faecal oral route of transmission
- source: faeces, specific foods
- no chronic carrier
Chronic hepatitis
- Hepatitis B, C and D virus
- parenteral route of transmission (vertical, sexual, percutaneous bloodborne)
- source: blood, body fluid
Different prevention methods for each
- pre/post exposure immunisation for HAV, HBV, HDV
- blood donor screening for HCV
- risk behaviour modification for HCV, HDV
- sanitation and clean water for HEV
NOTIFIABLE DISEASE IN HK
Hepatitis A route of transmission
Faecal-oral route of transmission (most important)
- env. contamination – contaminated seafood and water; shellfish cultivated in polluted water (HAV survives for long periods in wet environment)
- human-to-human – infected food handlers with poor hygiene (large amount of faecal shedding during incubation period); close personal contact with poor hygiene
Blood exposure very rare (viraemia is transient)
Hepatitis A clinical course and outcome
Incubation: 2-6 weeks
Acute hepatitis:
- manifestations depend on age
- most children are asymptomatic
- adults 70-80% symptomatic –> fever, malaise, jaundice (more likely if >14 yrs old)
- fulminant hepatitis is rare (<2%)
Outcome: clearance of virus and lifelong immunity
Hepatitis A diagnosis: infectious period, markers and their interpretations
Viraemia and faecal shedding begins prior (2-3 weeks) to symptom onset for short duration – direct detection not feasible
Anti-HAV IgM most useful – MARKER OF ACUTE INFECTION
- increases 1-2 wks after symptom onset and remain for up to 5-6 months
Anti HAV IgG – marker of immunity e.g. past infection or vaccination
Hepatitis A epidemiology: trends in endemic areas (disease rate, age affected, outbreaks), trend in HK (incidence, age affected, immunity in young adults, seasonality)
Highly endemic in developing countries
- variable disease rate
- peak infections in early childhood
- person to person transmission – outbreaks uncommon due to immunity from childhood infection
Moderate endemicity
- high disease rate, late childhood/ young adults
- food and waterborne outbreaks
Low endemicity
- low disease rate, young adults
- food and waterborne outbreaks
Very low endemicity
- very low disease rate, adults
- travelers transmit
- outbreaks uncommon
In HK:
- 1988 and 1992 large outbreaks
- incidence decreased over last 10 years but still common
- cases shifting to older ages (>25 yrs)
- only 30% young adults are immune (due to improving hygiene)
- seasonality: Jan-May
Hepatitis A prevention
Inactivated vaccine
- monovalent, 2 doses, 6-12 months apart
- bivalent (+HBV) - Twinrix - 3 doses, 0-1-6 months
Safe
Highly effective (protection starts 4 wks after 1st dose)
Pre-exposure prophylaxis for travellers
Not part of CIP
Hepatitis E clinical features: incubation, illness severity, outcomes (chronicity and fatality)
Incubation: 5 wks (2-8)
Illness severity increases with age
- asymptomatic
- fever, jaundice, malaise
Outcomes:
- chronic carrier is rare (only in immunocompromised)
- low fatality overall (clear infections)
- 15-25% fatality in pregnant women with Genotype 1 (fulminant hepatitis)
Hepatitis E diagnosis: faecal shedding period, markers and interpretation
Also have faecal shedding and viraemia prior to symptoms but with longer duration after symptom onset – direct detection by PCR is possible
Anti-HEV IgM most useful - MARKER OF ACUTE INFECTION
Anti-HEV IgG marker of past infection
Hepatitis E genotypes, epidemiology and routes of transmission
5 genotypes classified based on viral genome similarity
- 1-4 infect humans, 5 infects birds
- 1-4 have different distribution, transmission and animal reservoirs
Genotype 1 and 2: Asia, Central America and Africa - ENDEMIC
- no known animal reservoir
- faecal oral route (contaminated water cause outbreaks)
Genotype 3: N America, Europe, Australia and Genotype 4: East Asia - NON-ENDEMIC
- infects humans and animal species
- food-borne transmission (zoonosis) in sporadic cases
Hepatitis E in HK: major genotype, route of transmission and source, trend of disease, age affected, seasonality
Genotype 4 is majority
- infect human and pigs (31% roasters are HEV +ve)
- contaminated pig liver –> ZOONOSIS
- food-borne transmission, sporadic cases
Increasing trend of disease (>HAV as most common notified acute hepatitis)
- highest rates >55 yrs old
Only 15% young adults are immune
Most cases acquire infection locally (>80%)
M>F
Seasonality: Feb-May
Hepatitis E prevention (3)
Hygiene
- clean drinking water
- cooked food, fruit and veg
Animal reservoir
- well cooked internal organs
Vaccine
- not available in HK
