Avian Influenza | Bird Flu

Agent

Viral classification and genetic composition

Family: Orthomyxoviridae

Genus: Influenza
. Virions 80 to 120 nm in diameter
. May be filamentous
. Eight different segments of negative-stranded RNA; allows for genetic reassortments in single cells infected with more than one virus and may result in multiple strains that are different from the initial ones (see References: PHS, Voyles 2002)

Types: A, B, and C
. Type designation is based on the antigenic character of the M protein located in the virus envelope and the nucleoprotein within the virus particle.
. Influenza A virus causes human, swine, equine, avian, and marine mammal influenza and is the type associated with pandemic disease in humans.
. Influenza B virus causes disease in humans only.
. Influenza C virus causes a relatively mild illness in both humans and swine and occurs uncommonly.
. HPAI and LPAI are caused by influenza A viruses.

The virus envelope glycoproteins have hemagglutinin (HA) and neuraminidase (NA) activity; these characteristics are used to subtype the A, B, and C viruses.
. For influenza A viruses, there are 16 different HA antigens (H1 to H16) and nine different NA antigens (N1 to N9). Until recently, 15 HA types had been recognized, but a new type (H16) was isolated from black-headed gulls caught in Sweden and the Netherlands in 1999 and reported in the literature in 2005 (see References: Fouchier 2005).

. All 16 HA and 9 NA subtypes of influenza A can be found in avian populations; however, only subtypes H5 and H7 have caused HPAI.

. The H5 and H7 strains also are identifiable according to a nucleic acid sequence at the hemagglutinin cleavage site (see References: PHS).

. Environmental Survival of Avian Influenza Viruses

. Influenza A virus remains viable at moderate temperatures for long periods in the environment and can survive indefinitely in frozen material. It can survive for 4 days in water at 22oC and for over 30 days at 0oC (see References: PHS).

. Recent data from studies of H5N1 in domestic ducks have shown that H5N1 can survive in the environment for 6 days at 37oC (see References: WHO: Laboratory study of H5N1 viruses in domestic ducks: main findings).

. Inactivation of the virus occurs under the following conditions (see References: OIE 2002, PHS):

. Temperatures of 56oC for 3 hours or 60oC or more for 30 minutes

. Acidic pH conditions

. Presence of oxidizing agents such as sodium dodecyl sulfate, lipid solvents, and B-propiolactone

. Exposure to disinfectants: formalin, iodine compounds

Free Ask Question:

1. Definition of Avian Influenza?

2. Agent?

3. Hosts?

4. Transmission?

5. Key Outbreaks of HPAI in Domestic Avian Populations?

6. Current Status of H5N1 in Asia?

7. HPAI As a Biological Weapon?

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9. Differential Diagnosis?

10. Laboratory Diagnosis?

11. Treatment?

12. Prevention?

13. Outbreak Control in Poultr?