HEPATITIS C THEERAN GILL
CLINICAL FEATURES: INCUBATION PERIOD – LONG (15 -160 DAYS), WITH A MEAN OF 50 DAYS. ACUTE ILLNESS USUALLY MILD OR ANICTERIC. OVERT JAUNDICE IS SEEN IN ONLY ABT 5% OF PATIENTS. CHRONIC ILLNESS IS AN IMPORTANT PART IN HC. ABOUT 50 – 80% OF PATIENTS PROGRESS TO CHRONIC HEPATITIS WITH SOME DEVELOPING CIRRHOSIS AND HEPATOCELLULAR CARCINOMA.
EPIDEMIOLOGY: ONLY SEEN IN HUMANS. INFECTION IS MAINLY BY BLOOD TRANSFUSION & OTHER MODES OF CONTACT WITH INFECTED BLOOD OF BLOOD PRODUCTS. INJECTABLE DRUG ABUSERS, TRANSPLANT RECIPIENTS & IMMUNOCOMPROMISED PERSONS ARE AT HIGH RISK. SEXUAL TRANSMISSION IS PROBABLY LESS IMPORTANT. VERTICAL TRANSMISSION FRM MOTHER TO BABY MAY TAKE PLACE.
HCV: VIRUS NOT GROWN IN CULTURE BUT HAS BEEN CLONED IN E. coli. IT’S A 50 – 60 NM VIRUS WITH A LINEAR SINGLE STRANDED RNA GENOME, ENCLOSED WITHIN A CORE AND SURROUNDED BY AN ENVELOPE, CARRYING GLYCOPROTEIN SPIKES. IT RESEMBLES FLAVIVIRUS IN STRUCTURE & ORGANISATION & HAS BEEN CLASSIFIED AS A NEW GENUS Hepacivirus IN THE FAMILY Flaviviridae.
THE VIRUS SHOWS CONSIDERABLE GENETIC AND ANTIGENIC DIVERSITY. 6 DIFFERENT GENOTYPES & MANY SUBTYPES HAVE BEEN IDENTIFIED, INDICATING HIGH MUTABILITY. BECAUSE OF THIS DIVERSITY THERE IS LITTLE HETEROLOGOUS OF EVEN HOMOLOGOUS POSTINFECTION IMMUNITY IN HEPATITIS C.
LABORATORY DIAGNOSIS: STANDARD METHOD OF DIAGNOSIS IS ANTIBODY DETECTION BY ELISA. THE ANTIGENS USED ARE VARIOUS STRUCTURAL AND NON STRUCTURAL PROTEINS CLONED IN E. coli. HAVE BEEN 3 SUCCESSIVE GENERATIONS OF SUCH ANTIGENS, INTRODUCED TO IMPROVE SENSITIVITY & SPECIFICITY OF SEROLOGICAL DIAGNOSIS.
EVEN THE 3 RD GENERATION ELISA CURRENTLY IN USE, EMPLOYING NS-5 REGION PROTEIN AND SYNTHETIC PEPTIDES BECOMES POSITIVE ONLY MONTHS AFTER THE INFECTION AND SHOWS NON SPECIFIC REEACTIONS. CONFIRMATION BY IMMUNOBLAST ASSAY IS RECOMMENDED. HCV INFECTION ANTIBODIES APPEAR IRREGULARLY AND LATE, LIMITING THEIR DIAGNOSTIC UTILITY.
IDENTIFICATION OF HCV RNA IN BLOOD PROVIDES MORE SENSITIVE AND SPECIFIC RESULTS WITHIN FEW DAYS OF EXPOSURE TO HCV. MOLECULAR METHODS LIKE PCR AND BRANCHED DNA ASSAY ARE EMPLOYED FOR THE PURPOSE.
PROPHYLAXIS: BLOOD SCREENING. PASSIVE IMMUNISING AGENT IS AVAILABLE.
TREATMENT: PROLONGED TREATMENT WITH INTERFERON ALPHA, EITHER ALONE OR IN COMBINATION WITH ANTIVIRAL AGENTS LIKE RIBAVIRIN HAS BEEN REPORTED USEFUL IN SOME CASES.
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