
a. Explain the relationship between herd immunity and the development of influenzal pandemics.
b. Why will herd immunity be lacking if antigenic shift or drift occurs?

To analyze:
- The relationship between herd immunity and the development of influenzal pandemics.
- Why herd immunity would be lacking if antigenic shift or drift occurs
Introduction:
Viruses may come in more than one strain, varying in their surface antigens. Herd immunity refers to the general resistance of a population to a particular strain of a virus.
Explanation of Solution
- When herd immunity for a strain of the influenza virus is high, it means that most individuals in the population won’t be affected by that strain. Consequently, the strain is less likely to spread in the population. This also means that there are fewer instances when the strain reaches other populations during travel, especially if the other population also has high immunity. When herd immunity against a strain is lacking, the strain will circulate in the population, and there will be many more chances of exposure to other populations due to travel or migration. This is what leads to influenza pandemics.
- Herd immunity is a result of the immune systems of the individuals in a population having the ability to recognize an antigen on the surface of the virus. When the immune system cannot immediately recognize the antigen, it cannot react fast enough to prevent infection. During antigenic drift and shift, the composition of the antigenic proteins change as a result of mutation or gene exchange. Therefore, during such events new strains of the virus are created, and herd immunity for these new strains will be lacking.
Low herd immunity increases the chances for influenza pandemics to occur. When antigenic drift or shift occur, there are changes in the surface antigens of the virus. This means that the immune systems of the individuals in the population cannot immediately recognize the new strains of virus that have formed. Therefore, her immunity is lacking during such events.
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Chapter 25 Solutions
Foundations in Microbiology
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