Hepatitis B virus
DR HADEEL FADHIL
@ Identification: * Onset is usually insidious with anorexia, vague abdominal discomfort, nausea, vomiting, sometime arthralgia & rash, often progressing to jaundice. Fever may be absent or mild. * case fatality rate in hospitalized patients is about 1%. * Chronic HBV infection is found in 0.1-20% .
. 15-25% of persons with chronic HBV infection will die either from cirrhosis or hepatocellular CA.
* Diagnosis: demonstration in sera of specific antigen &/or AB 1- HBs Ag & AB
2- HBc Ag & AB 3-HBe Ag
& AB
Infectious agent: HBV (Hepadnavirus, DNA virus).
@ Occurrence:
* world wide, WHO estimates that more than 2 billion persons(including 350 million who are chronically infected), each year one million die as a result of HBV infection & over 4 million of new cases occur.
*In countries where HBV is highly endemic (HBs Ag prevalence 8% or higher), most infection occur during infancy & early childhood.
* in countries where HBV is intermediately endemic (HBs Ag prevalence 2-7%) & occur in all age group.
* In countries with low endemicity (HBs Ag prevalence less than 2%), most infection occur in young adult especially high risk group
@ Reservoir: human.
@ Mode of transmission:
1- Body substances: blood & blood products, saliva, CSF, peritoneum, pleura, pericardial & synovial fluid, amniotic fluid, semen & vaginal discharge.
2-transmission occur by percutanous (IV, IM, SC & intradermal).
3- Sexual or household contact with infected persons. 4- Perinatal transmission from mother to infant.
5- Injecting drug use.
6- Organ transplantation.
7- Nosocomial infection — HBV is the most commonly transmitted blood-borne virus in the healthcare setting. Transmission generally occurs from patient to patient or from patient to health care personnel via contaminated instruments or accidental needle stick
.
@ Risk group:
1- Sexually active heterosexual men & women.
2- Men who have sex with men.
3- Sexual paternal & household contacts of HBs Ag positive persons.
4- Health worker who contact with blood or blood contaminated body fluid.
5- Hemodialysis patients.
6- Patients with bleeding disorder who receive blood products.
7- International travelers.
8- Injectable drug addicts, tattooing.
9- Patients with chronic liver diseases.
@ Incubation period: 60-90 days.
@ Period of communicability: all persons who are HBs Ag positive are potentially infectious ,blood remain infected many weeks befor the onset of first symptoms & to remain infective through the acute clinical course of the disease.
@susceptibility & resistance:
Susceptebility is general. HBV infection usually mild but the severity increase with age. Protective immunity follows infection if antibody to HBs Ag (anti-HBs) develops & HBs Ag is negative.
@Methods of control:
A- Preventive measures:
1- Effective HB vaccine: routine infant immunization should be the primarily strategy to prevent HBV infection.
*for infant at 0, 2, 6 month are routinely given as a part of expanded program of immunization in Iraq injected in anterolateral part of thigh.
* For high risk group adult the vaccine will given at 0, 1, 6 months
Immunity against HBV is believed to persist for at least 15 years after successful immunization.
2- Adequate sterilize all syringes & needles, discourage tattooing.
3- In blood bank, all donated blood should be tested for HBs Ag.
4- Limit administration of unscreened whole blood or potentially hazardous blood products.
5- Medical & dental personals that are infected with HBV & are HBe Ag positive should not perform invasive procedures.
B- Control of patient, contact & immediate environment.
1- Obligatory case report to local health authority.
2- Isolation: precaution to prevent exposures to blood & body fluids.
3- Concurrent disinfection of equipments contaminated with blood or infectious body fluids.
4- Quarantine: none.
5- Immunization of contact: products available for post exposure prophylaxis include HB IG & HB vaccine.
HB IG should administer as soon as possible after exposure:
a- infant born to HBs Ag positive mother should be given a single dose of HB IG (0.5 ml IM), & vaccine within 12 hr of birth.
b- After percutenous (e.g. needle stick) or mucus membrane exposure to blood that contains or might contain HBsAg
C- after sexual exposure to a person with acute HBV infection, a single dose of HBIG (0.06 ml/ kg) is recommended. Post exposure prophylaxis is recommended for all non vaccinated individuals who are exposed to blood or infectious secretions. The first dose vaccine should be given as early as possible and within 12 hours of exposure. If the source is known to be HBsAg positive, one dose of HBIG should be administered at the same time in another site. The other two doses of vaccine should be administered according to the usual schedule.
In individuals who have been vaccinated and have a documented response, no post exposure prophylaxis is required. Individuals who have no post vaccination testing will require a second course of vaccination unless anti-HBs is detectable at the time of exposure. Individuals who are documented to be non-responders will require two doses of HBIG given one month apart.
6- Specific treatment: no specific treatment is available for acute HB. Alpha interferon, lamivudine for chronic HBV infection.