DEFINITION: Primary infection of the liver caused by a small group of viruses (hepatotropic viruses) having a particular affinity for the liver is known as Viral Hepatitis.
HEPATITIS VIRUS A (HAV) :
HAV causes benign self limited, acute, transient infectious hepatitis. It does not lead to chronic hepatitis or a carrier state and only rarely does it cause massive liver necrosis (Fulminant Hepatitis)
Year of Identification: 1973
Morphology: HAV is a small, non enveloped virus, 27nm(nanometer) in diameter, cubical in shape and contains single stranded RNA.
HAV occurs throughout the world and is endemic in countries with substandard hygiene and sanitation. Children are more commonly affected but severity increases with age. In India about 90% of children are serologically positive by 10 years of age. When the sanitation and hygiene is improved, the morbidity increases.
Incubation Period: 15-45 days
Mode of Infection:
- Faecal-oral route: HAV is shed in the stool for 2-3 weeks before and 1 week after the onset of Jaundice. Thus close personal contact with an infected individual or faecal oral contamination during this period causes infection. This explains the occurrence of outbreaks in institutional settings such as schools and nurseries. HAV is spread by ingestion of contaminated water and food (esp. sea food).
- Occasionally by infusion of infected blood or contaminated needle during the stage of transient viraemia.
Immunological markers of HAV:
Specific antibody of IgM type appears in blood against the HAV at the onset of symptoms. It is a reliable marker of acute infection. As the IgM titer rises, the faecal shedding of the virus ends. The IgM response usually begins to decline in few months and is followed by the appearance of IgG anti HAV. During convalescent phase, the titer of IgG starts rising which persists for life time, proving protective immunity against re-infection by HAV.
Prevention and Control of HAV
- Isolation of the patient
- Disinfection of contaminated water and food
- Disposal of night soil
- Immunization: By human immunoglobulin derived from pooled plasma of healthy donors. It induces passive immunity. Immunoglobulin in 0.02 mg/kg IM should be given before exposure to the virus or during incubation period to the household and institutional contacts, elderly people and to pregnant women.
HEPATITIS B VIRUS (HBV)
HBV is the most versatile of the hepatotropic viruses. It can produce the following:
- Acute Hepatitis
- Chronic nonprogressive hepatitis
- Chronic active or progressive hepatitis ending in cirrhosis.
- Fulminant hepatitis with massive liver necrosis.
- Hepatocellular carcinoma
SCHEMATIC PRESENTATION OF THE POTENTIAL OUTCOME OF HEPATITIS B INFECTION IN ADULTS
ACUTE INFECTION WITH HBV
Subclinical Disease 60-65%
Acute Hepatitis 20-25%
Healthy Carrier 5-10 %
Persistent Infection 4%
Chronic Hepatitis: 20-50% Cirrhosis 10% of cirrhosis leads to hepatocellualr carcinoma —- death
Year of identification : 1965
Globally liver disease caused by HBV is an enormous problem, with an estimated worldwide carrier rate of more than 300 million. HBV is endemic in tropical and developing countries. About 3/4th of the world population is living in highly endemic areas. In developing world HBV is more common in childhood whereas in developed countries adults are at high risk due to their life style.
MORPHOLOGY OF HBV
The mature HBV is a 42nm, spherical, double layered “Dane Particle”. It contains double stranded DNA in its core of 28 nm, enveloped with a capsule of Protein, Lipid and Carbohydrate. The antigenic activity of the core DNA is designated HBC(Core)Ag. The inner part of the envelope has its own antigen known as HBeAg. The outer surface of the envelop contains a surface antigen called HbsAg, which is also known as “Australian Antigen”, because it was first identified by Bluberg in the serum of an Australian aborigine in the course of genetic studies.
Incubation Period: 30-180 days (mean 100 days)
Reservoir of Infection: Man is the only source of infection
Period of communicability:
HBV is present in the blood in the last stages of incubation period and during active episodes of acute and chronic hepatitis. It is also present in all physiologic body fluids, with the exception of stool.
- Blood : main source of infection
- Body secretions: semen, saliva, sweat, tears, breast milk, vaginal secretions and path. effusions
Mode of transmission:
1. Parental Route: By infective blood and blood products
- Blood transfusion
- Contaminated needles
- Accidental prick of skin
- Handling of infected blood
- Accidental inoculation of minute quantity of blood during surgical and dental operation
- Traditional tattooing
- Ear piercing
- Nose pricking
- Ritual circumcision
- Accidental percutaneous inoculation by razors and tooth brush
- 2. Vertical Transmission: Spread from an infected mother to a neonate during birth is common. It often leads to the carrier state for life. Transplacental infection to foetus in uterus may occur rarely
- 3. Sexual transmission: By intimate contact or sexual intercourse
4. By other route: saliva, sweat, tears, urine, menstrual blood, colostrums etc.
High Risk Group for HBV:
- I V drug users
- Gays-male homosexuals
- Close contact with infected person
- Chronic haemodialysis
- Medical / Nursing personnel, dentist, surgeon, intensive care unit staffs, liver unit, endoscopy unit, oncology unit and lab staff handling blood.
Immunological marker of HBV
- HBsAg or Australia Antigen: it is the first antigen to appear in blood in HBV infection. It appears during the incubation period and peaks during the acute stage of the disease. It usually declines to undetectable level in 3-6 months. Presence of HbsAg in blood is the diagnostic hallmark of HBV infection.
- HBeAg: It appears in the serum soon after the HbsAg and indicates active viral replication. Persistence of HbeAg is an important clinical indicator of continued active viral replication , continued infectivity and probable progression to chronic hepatitis.
- Anti-HBc Antibody: Antibodies against the viral core antigen, anti-HBc are the first to become detectable after exposure to HBV. Anti HBc of IgM type appears in the serum shortly before the onset of symptoms and coincides with the onset of elevated transaminases (SGOT, SGPT) , indicating hepatic injury. Over months the IgM antibody is replaced by IgG type of anti-HBc. So an elevated level of IgM anti-HBc indicates a recent acute infection.
- Anti-HBe Antibody: It appears shortly after the disappearance of HbeAg, implying that the acute infection has peaked and the disease is on decline.
- Anti-HBs Antibody: It appears in the patient’s serum a few weeks to months after the disappearance of HbsAg. This interval is known as “window period”, during which Anti-HBe are the only markers of the disease. In most of the patients , Anti-Hbs persists for life, confirming protection against any further HBV infection.
Prevention and control of HBV infection:
- Isolation of the patient
- Disinfection of contaminated material
- Use of fresh needles
- Adequate sterilization of all instruments
- Detection of carriers and their treatment
- Carriers should be advised to use barrier contraceptives
- No sharing of razors, toothbrushes with the carriers
- Before Exposure: Hepatitis B vaccine at 0,1 and 6 months to high risk groups e.g. health workers, gay men, IV drug users, haemodialysis patients, hemophiliacs and all neonates in endemic areas .
- After Exposure: Hepatitis B immunoglobulin (HBIG) 0.06 ml/Kg I.M immediately after needle stick, within 14 days of sexual exposure, or at birth in case of HBsAg positive mother plus vaccine series.
HEPATITIS C VIRUS (HCV)
Persistent infection and chronic hepatitis are the hallmarks of HCV infection which usually leads cirrhosis of liver in more than 50% of cases.
Year of identification: 1989
Morphology: HCV is a small enveloped single stranded RNA virus with a 30-60 nm diameter.
Mode of transmission:
- Parental: inoculations and blood transfusion
- Vertical transmission
- Close personal contact – sexual contact
Incubation Period: 20-90 days (mean: 6-12 weeks)
Immunological markers: presence of anti-HcV in the patient’s serum. Episodic elevation of serum transaminase (SGOT, SGPT) with intervening normal or near normal periods.
HEPATITIS D VIRUS (HDV)
It is also known as “delta agent” and “hepatitis delta virus”. It is a unique virus with defective replication, causing infection only when it is encapsulated by HbsAg. This HDV is totally dependent on HBV for multiplication and causes hepatitis only in the presence of HBV.
Year of Identification: 1977
Morphology: HDV is a 35 nm, single stranded double shelted particle which resembles the “Dane Particle” of HVB.
Mode of transmission: HDV infection occurs in the following ways:
- Acute co-infection: it occurs after exposure to serum containing both HDV and HV. The HBV first becomes established to provide the HbsAg necessary for the development of complete HDV virions.
- Superinfection: Exposure of a chronic carrier of HBV with a new inoculation of HDV results in disease about 30-50 days later.
Incubation period: 30-50 days in superinfection
Immunological Markers of HDV:
- Presence of IgM anti-HDV is the most reliable indication of recent HDV infection.
- Presence of IgM anti-HDV and IgM anti-HbcAg in case of acute co-infection.
- Presence of HbsAg and anti-HDV in case of superinfection.
Prevention: Hepatitis B vaccine (non carriers only)
HEPATITIS E VIRUS (HEV)
HEV hepatitis is an enterically transmitted infection occurring primarily in young to middle aged adults. A characteristic feature of HEV infection is the high mortality rate among pregnant women, approaching 20% HEV does not cause chronic hepatitis or persistent viremia.