Hepatitis B

Generalities
Agent	- Hepatitis B virus HBV, hepadnovirus - 4 subtypes: adw, ayw, adr, ayr - 8 genotypes: A-H
Incubation period	45-180 days (60-90 days)
Period of transmissibility	If HBs Ag(+) or HBe Ag(+)
Reservoir	Humans
Modes of transmission	- Person-to-person transmission: body fluids (blood, blood products, saliva, CSF, pleura, peritonial, percardial, synovial fluid, amniotic liquid, semen, vaginal secretions) - Modes: percutaneous and mucosal exposure to infective body fluids (sexual, perinatal, injectable drugs, nosocomial...)
Clinical presentation	- Clinical jaundice. May be asymptomatic - Complications: chronic hepatitis, cirhhosis, hepatocarcinoma cancer. Chronic infection varies with age: 90% if infected <1 year, 20-50% if infected at 1-5 years old, 1-10% if infected at older ages
Resources
Case definition	MOPH circular no. 111 (2006)
Forms	- General reporting form - Hepatitis B/C/D investigation form
Data	Refer to "Surveillance Data"