Question

There have been relatively few human cases of avian flu to date. Provide two reasons why avian viruses are more likely to infect birds than humans?

Answer 1

Answer:

Bird flu commonly termed as Avian flu, it is caused by influenza viruses that occurs naturally among all wild birds. These viruses infect most likely birds, including humans.

Influenza A viruses have eight separate gene segments, these segmented genome allows of influenza A viruses from different species to mix and create new virus.

Transmission: Animals to Humans

i. Directly from birds or Avian influenza virus contaminated environments to people

ii. Through an intermediate host

examples:

In 1998, only H1N1 viruses circulated widely in U.S. pig population. However, in 1998 , H3N2 viruses from humans were introduced into pig population and caused widespread of disease among the pigs. Recently H3N8 viruses from horses have crossed over and caused outbreaks in dogs.

Mechanism:

Genetic alteration occuring in an infectious agent that causes a dramatic change in protein called antigen which stimulate antibody production by the immune system of human and animals is called Antigenic Shift

Influenza virus has 8 segments, which during viral replication susceptible to a type of genetic exchange known as genetic reassortment. These genetic reassortment can result in antigenic shift

H1N1 , H = hemagglutinin

           N = Neuraminidase

Influenza hemaggluttinin (HA) is a type of hemagglutinin found on the surface of the influenza viruses

Functions of HA :

i. To identify target vertebrate cell by binding to host cells receptor and

ii. Allowing the entry of viral genome into target cells by causing the fusion of host membrane with the viral membrane