Hepatitis A, B and C viruses: Transmission and Prevention

• HAV (hepatitis A virus) transmits via the fecal-oral route, often through contaminated food/water or contact with an infected person.
• HAV causes acute, self-limiting illnesses and does not lead to chronic infection.

Stages of HAV Infection:

• Incubation.
• Acute hepatitis.
• Convalescence (recovery).
• HAV vaccination is highly effective.

HBV

• HBV(hepatitis B virus) causes both acute and chronic infections and is responsible for high rates of liver disease, liver cancer, and death.
• Prevent HBV infection using vaccination and focuses on immunization of all children and at-risk adults.
• Anti-HBV drug therapy aims for viral suppression, immune control, and to prevent progression of HBV-related liver diseases.
• Tenofovir or Entecavir is the initial therapy for chronic HBV because these agents have a high barrier to resistance
• Pts undergoing immunosuppressive therapy or chemotherapy are screened for HBV infections and may require HBV therapy

HCV

• HCV (hepatitis C virus) is an insidious, blood-borne infection, and universal, one-time screening is recommended for all aged 18 and over.
• Hepatitis C infections cause significant morbidity including extrahepatic manifestations and mortality.
• Patients with chronic hepatitis C are at risk for end-stage liver disease, cirrhosis, liver transplant, and death as a result of their infection.
• Direct-acting antivirals (DAAs) are effective and well tolerated

Viral Hepatitis

• Major hepatotrophic viruses responsible for viral hepatitis are hepatitis A, B, C, delta (D), and E.
• Hepatitis A and E are spread via fecal-oral contamination, while B, C, and delta are transmitted parenterally.
• Infection with delta hepatitis requires coinfection with hepatitis B.
• Hepatitis A and B are vaccine preventable.
• Hepatitis C has no vaccine.

Epidemiology of Hepatitis A

• Hepatitis A is a self-limiting, acute viral infection of the liver presenting a health risk worldwide, rarely fatal.
• Hepatitis A spreads primarily through the fecal-oral route by person-to-person contact or ingestion of contaminated food/water.
• Prevalence is linked to resource-limited regions with poor sanitation and overcrowding.
• Patients with preexisting chronic liver disease, e.g., HCV, face increased risks of developing fulminant HAV.
• Children can contribute to the spread of the disease because they remain infectious for a long time as asymptomatic carriers
• Household or close personal contacts of an infected person are at high risk for infection.
• Outbreaks are observed among specific patient groups include persons who inject drugs (PWID)

Etiology of Hepatitis A

• Hepatitis A is a nonenveloped ribonucleic acid (RNA) virus in the PICORNAVIRIDAE family.
• It is stable in low pH (acidic) environments and in freezing to moderate temperatures.
• Inactivation occurs when disinfecting with a 1:100 dilution of sodium hypochlorite (bleach) in tap water or heating foods to a minimum of 85°C (185°F) for 1 minute
• Chlorination of water also effectively kills HAV in water systems
• Common modes of transmission: contaminated water or ice, foods prepared using contaminated water or shellfish harvested from contaminated water
• Access to clean water and proper handwashing are critical in preventing the transmission of HAV.

Pathophysiology of Hepatitis A

• Hepatitis A is acute, self-limiting, and confers lifelong immunity.
• Hepatitis A's life cycle classically begins with ingestion of Hepatitus A
• Absorption of HAV occurs in the stomach or small intestine and allows entry into the circulation for uptake by the liver.
• Replication occurs within hepatocytes and GI epithelial cells.
• New virus particles are released into the blood and secreted into bile by the liver, where they are reabsorbed or excreted in the stool.
• The enterohepatic cycle of HAV continues until interrupted by antibody neutralization.

Clinical Presentation of Hepatitis A

• Incubation period of Hepatitis A is approximately 28 days, with a range of 15 to 50 days.
• Symptoms includes fever, jaundice, and scleral icterus (yellowing of the whites of the eyes).
• Hepatomegaly is evident on physical exam.
• Less common signs includes splenomegaly, skin rash, arthralgia.
• Children < 6 years are typically asymptomatic and can shed the virus for long periods of time.
• Peak fecal shedding of the virus precedes the onset of symptoms & liver damage
• Begins with a preicteric or prodromal period which lasts for around 2 months
• Liver enzyme levels increase within the first weeks of infection, with peak elevation around the fourth week.
• ALT exceeds AST in acute phase and can be >1,000 IU/L and normalizes by the eighth week.
• Conjugated bilirubinemia causes evident dark urine is an early sign of jaundice.
• Gl symptoms may persist or subside during the icteric period; hepatomegaly may be present.
• Duration of icteric period averages between 7 and 30 days, varies, and corresponds to disease duration

Diagnosis of Acute HAV

• Serological testing detects IgM and IgG anti-HAV to diagnose infection and immunity.
• IgM anti-HAV indicates recent or current HAV infections; appears early
• IgG anti-HAV replaces IgM after the acute phase and indicates host immunity following the acute phase of the infection, as well as long-term immunity (past infection or vaccination)
• Total anti-HAV detects both IgM and IgG and shows current or past infection, or vaccination status.
• Detectable total anti-HAV with negative IgM indicates resolved infection and long-term immunity (Total anti-HAV (+) but IgM (-) = have resolved their infection)

Treatment of Hepatitis A

• HAV does not lead to chronic infections and patients are expected to fully recover w/o clinical sequelae
• Complete clinical resolution is the ultimate goal and almost all infected will have this resolution
• Treatment includes preventing complications from the infection & reducing infectivity and transmission
• Prevention and prophylaxis - keys to managing this vaccine-preventable virus
• No specific treatment options exists & receives supportive care
• Good hand hygiene is key in preventing transmission.
• Passive immunity with Ig (ready-made antibodies) for preexposure (travelers to high-risk areas) and postexposure prophylaxis (after contact with HAV)
• Short term protection

Prevention of Hepatitis A

• Hepatitis A is easily preventable with vaccination
• Since children often serve as reservoirs so vaccine programs target children as the most effective means to control HAV.
• Complete HAV VACCINATION RECOMMENDATIONS is available from the CDC includes: Persons traveling, children from 1-2 years, children up to 18, men who have sex, health workers, etc
• All children from 1 -2 years has immunization in routine schedule
• Vaccine: Persons at risk for worse outcomes with HAV infections - include persons over the age of 40 are vulnerable
• There are 2 types of vaccines inactivated virus HAVRIX® and VAQTA® which both pediatric ( 12 month (1 yr) and older and adult 18 years and older) which the CDC vaccines
• A booster shot achieves the highest possible antibody titers is recommended
• For postexposure prophylaxis - the HAV Vaccine prevents the HAI
• For all people at high risk of endemic infections & those from high risk regions
• Testing before serology is generally not recormmended, but could be cheaper in some countries

Immunoglobulin (Ig)

• Immunoglobulin A sterile preparation of concentrated antibodies against HAV that protection by passive transfer of antibody

• In 2017, recommendations for increased dose of Ig were established due to concerns for declining HAV antibody from donors

• Has recommendation useful w vaccine & it it needed w/n 2 vweks in high risk indivisuals like old ppl & those at risk / immuno compromised etc

• The vaccine induces active immunity to give longer time protection after hepatitis

• Ig has effects in is most effective if given int he incubation period of the infection

• Patient who receive hepatitis at least dose, so should not need pre/post exposure & can be given w both intravenous ir intramuscular IV/IM INJECTION

• Sides effects - anaphylaxias / contraindication

• Immunoglobulin dosing same for adults & children

Hepatitis B.

• Chronic HBV infection is a major public health issue & poses risk fo rdeath frm liver diseases
• Vaccination prevention
• C'S ACIP -
• Low public awareness risk

Etilogy

• At least 10 + Hep B types

Pathophysiology

• Replication to cell surface receptors
• Virion DNA shielding = integrated into Chromsomal DNA