MMSC 415 quinary (5th)

Hepatitis D Virus (HDV)

A defective ssRNA virus (delta agent) that requires active HBV infection and HBsAg for its outer envelope and replication.

HDV Transmission

Parenteral exposure (blood, body fluids, contaminated needles) and sexual contact, matching HBV transmission routes.

HDV Coinfection

Simultaneous infection with HBV and HDV; usually leads to a self-limiting acute illness with less than 5% developing chronic infection.

HDV Superinfection

HDV infection acquired by an individual with chronic HBV; rapidly accelerates liver disease, causing chronic HDV in >80% of patients and severe cirrhosis.

HDV Serological Diagnosis

Infection indicated by positive HBsAg, positive anti-HBc IgM, positive anti-HDV antibodies, and confirmed by HDV RNA PCR.

HDV Prevention

Prevention of initial HBV infection via the Hepatitis B vaccine, as HDV cannot infect without HBV present.

Hepatitis A Virus (HAV)

A non-enveloped, icosahedral ssRNA picornavirus containing a single serotype and a hepatitis A antigen nucleocapsid.

HAV Transmission

Fecal-oral route via ingestion of contaminated food/water or close person-to-person contact.

HAV High-Risk Groups

International travelers, men who have sex with men (MSM), illicit drug users, individuals with occupational exposure, and homeless populations.

HAV Pathogenesis

Acute liver infection with replication in hepatocyte cytoplasm; ranges from asymptomatic (<6 y.o.) to acute jaundice, resolving without chronic infection.

HAV Serology

Diagnostic detection of Anti-HAV IgM during acute disease and Anti-HAV total (IgM + IgG) or HAV RNA PCR.

HAV Prevention & Post-Exposure

Inactivated HAV vaccines (e.g., HAVRIX, VAQTA, Twinrix) and immune globulin administered within 2 weeks of exposure.

Hepatitis C Virus (HCV)

An enveloped ssRNA virus belonging to Flaviviridae with 7 genotypes, most commonly genotypes 1a, 1b, 2, and 3 in the U.S..

HCV Primary Transmission

Parenteral exposure, most commonly injection drug use in the U.S., as well as needle sticks and body fluid exposure.

HCV Chronicity Rate

50% to 70% of individuals infected with HCV fail to clear the virus and develop a chronic infection.

HCV Non-Protective Antibodies

Antibodies formed against HCV do not confer lifelong immunity due to rapid viral mutation driven by an error-prone polymerase.

HCV Screening Protocols

Universal screening recommended for all U.S. adults >18 years (once per lifetime) and pregnant women during each pregnancy.

HCV Confirmatory Test

Quantitative HCV RNA Nucleic Acid Testing (NAT/PCR), which detects viral RNA within 1–2 weeks post-exposure and measures response to treatment.

Epclusa (sofosbuvir/velpatasir)

A pan-genotypic (1–6) oral direct-acting antiviral (DAA) combination targeting NS5B polymerase and NS5A that cures up to 98% of chronic HCV in 12 weeks.

Mavyret (glecaprevir/pibrentasvir)

An oral DAA combination targeting NS3/4A protease and NS5A that cures 95–99% of chronic HCV genotypes 1–6 in an 8-week course.

Hepatitis E Virus (HEV)

A non-enveloped ssRNA virus (Hepeviridae, genotypes 1–4) transmitted primarily via the fecal-oral route through contaminated drinking water or undercooked meat.

HEV Serological Diagnosis

Detection of Anti-HEV IgM during the acute phase (2–4 weeks post-exposure), Anti-HEV IgG during convalescence, or HEV RNA PCR.

HEV Prevention & Treatment

Sanitation, safe food/water preparation, supportive therapy, and off-label antivirals (ribavirin/interferon) for severe/chronic cases; no U.S. vaccine available.