HAV - THE HEPATITIS A VIRUS | MICROBIOLOGY NOTES

HAV – THE HEPATITIS A VIRUS



INTRODUCTION TO HEPATITIS A VIRUS (HAV)

⇒ Hepatitis A virus (HAV) was first demonstrated by the Feinstone & co-workers in 1973 by using immunoelectron microscopy (IEM).

⇒ HAV causes Type A hepatitis or Infectious Hepatitis, a subacute disease occurring mainly in children & young adults.

MORPHOLOGY OF HEPATITIS A VIRUS

⇒ HAV is a 27 nm, non-enveloped, single-stranded RNA virus with an icosahedral symmetry.

⇒ HAV belongs to the Picornavirus family.

⇒ Only one serotype of this virus exists.

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TRANSMISSION ROUTE OF HEPATITIS A VIRUS

⇒ The Hepatitis A virus enters the body by the oral route through contaminated food, water or milk.

RESISTANCE SHOWN BY HEPATITIS A VIRUS

⇒ HAV is resistant to inactivation by heat at 60o C for 1 hour, ether & to pH 3, can survive at 4o C or below.

⇒ HAV is destroyed by autoclaving at 121oC, boiling for five minutes, formaldehyde (1:4000), by chlorine at 10-15 ppm for 30 minutes & inactivate by UV rays.

CLINICAL FEATURES OF HEPATITIS A VIRUS

⇒ The large majority of infections are asymptomatic.

⇒ The incubation period is 2-6 weeks.

⇒ Symptoms include Fever, Malaise, Anorexia, Nausea, Vomiting, Liver tenderness, usually subsides with Jaundice.

⇒ Rapidly fatal fulminant hepatitis is very rare.

LABORATORY DIAGNOSIS OF HEPATITIS A VIRUS 

⇒ Specimen:- Feces or serum may be collected for the demonstration of the virus or its antibodies.

⇒ Direct demonstration:– The virus can be visualized by IEM in feces.

⇒ Serology:– IgM anti-HAV antibody appears during the late incubation period, reaches peak levels in 2-3 weeks & disappears after 3-4 months. IgG antibodies also appear & peaks in 3-4 months and persist much longer. ELISA kits are used to detect the presence of these antibodies in the feces & also can be detected by radioimmunoassay.

⇒ Biochemical tests:– Liver function tests such as serum alanine aminotransferase (ALT) and bilirubin level supplements the diagnosis.

PROPHYLAXIS OF THE HEPATITIS A VIRUS INFECTION

⇒ Improved sanitation & prevention of fecal contamination of food & water.

⇒ HAV vaccination is available, the full course consists of two intramuscular injections of the vaccine. Protection lasts for 10-20 years.

⇒ One attack of the disease gives life-long protection against HAV.

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HAV – THE HEPATITIS A VIRUS

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