Question

Analysis of the 1918 and 2009 flu epidemics reveals that the most likely scenario was that ________.

1) the virus causing these outbreaks were derived from a single strain within which significant mutations changed the protein hemagglutinin

2) these viruses switched from using RNA to using DNA

3) the virus ultimately arose in birds, jumped to pigs, and then was able to switch to humans

4) strong selection produces particularly virulent flu strains with predictable periodicity

Answer 1

The 1918 and 2009 flu epidemics were likely caused by a virus strain that underwent significant mutations in the hemagglutinin protein through an antigenic shift, creating a new virulent strain against which people had little immunity.

Step-by-step explanation:

Analysis of the 1918 and 2009 flu epidemics reveals that the most likely scenario was the virus causing these outbreaks were derived from a single strain within which significant mutations changed the protein hemagglutinin. These mutations, known as antigenic shifts, result in novel virus forms that can be highly virulent and capable of causing pandemics, as individuals have little to no preexisting immunity against these new variants. It is understood that these shifts occur during simultaneous infection of a cell with two different influenza viruses, resulting in a mixed genome.

The 1918 flu, commonly known as the Spanish flu, and the 2009 H1N1 pandemic are both associated with this mechanism. Conditions such as crowding and close contact between animals and humans in farms significantly contribute to the emergence and spread of new influenza strains. Surveillance by organizations like the World Health Organization is key in monitoring these strains to prevent global crises.