[Campbell Biology P.459] The H5N1 avian influenza strain is noted for its high mortality rat... | Practice Question

The H5N1 avian influenza strain is noted for its high mortality rate >50% but has not yet caused a global epidemic. Based on the text, what is the primary reason for this, and what critical insight did the 2011 ferret study provide about its potential future threat?

  • A: H5N1 primarily infects humans who consume contaminated poultry, and the ferret study showed it needs significant human adaptation to spread.
  • B: H5N1 has limited person-to-person transmissibility, but the ferret study demonstrated that only a few mutations could make it transmissible through the air between mammals.
  • C: H5N1 is easily neutralized by human immune responses, and the ferret study confirmed its inability to infect human cells without reassortment.
  • D: H5N1 cannot reassort with human influenza strains, and the ferret study focused on its vaccine efficacy rather than transmission.

Explanation

The text clearly states that H5N1 has not caused an epidemic because 'nearly all cases have been the result of transmission from birds to people, rather than person-to-person.' It further explains that the ferret study found 'only a few mutations of the avian flu virus were sufficient to allow infection of cells in the human nasal cavity and windpipe,' and the virus 'became transmissible through the air' between ferrets, indicating a high potential for it to evolve into a human-transmissible strain.