Avian Influenza

Introduction:

• Has not become an epidemic till now because:
• Human to human transmission is rare.
• Causative agent:
• H5N1 (Type A Influenza virus)
• Avian Influenza is a Pandemic:
• Origin from Hong Kong (1997)

Avian Influenza

• Primarily infect birds
• Also known as ‘Bird flu’ or ‘Highly pathogenic avian influenza’
• Antigenic type H5N1 is of greater concern because:
•  infection is frequently lethal in humans approximately 60%
• Since 2003 the virus is spreading throughout the world in wild and domestic birds.
• Acquired by close contact with domestic birds
• Cause widespread infection in the human body instead of infection being limited to the lung.

Pathophysiology:

• The tissue tropism of H5N1 influenza is increased due to :
• the unusual structure of its hemagglutinin protein
• Cleavage of viral hemagglutinin by host proteases is required for the influenza virus to enter host cells.
• Fortunately, the transmission of the current H5N1 virus is inefficient

Treatment:

Drug of choice:

•  Oseltamivir (Tamiflu) 75 mg BD x 5 days 
• contraindicated in infants

Vaccine Avian Influenza:

• On April 17, 2007, FDA licensed the first vaccine in the United States.
• This inactivated influenza virus vaccine 
• Age group:
• 18 through 64 years.
• This vaccine is derived from:
•  A/Vietnam/1203/2004 influenza virus.

Two-dose regimen. :

• One 90 microgram dose is given intramuscularly, in the upper arm
• Second 90 microgram dose is given in the same manner, 28 days later.