To cause a human pandemic, the H5N1 avian flu virus would have to
a. Spread to primates such as chimpanzees.
b. Develop into a virus with a different host range.
c. Become capable of human-to-human transmission.
d. Become much more pathogenic.

Verified step by step guidance

1. Understand the nature of the H5N1 avian flu virus: It primarily infects birds and occasionally humans, but it does not easily spread between humans.
2. Consider the requirements for a virus to cause a pandemic: A pandemic occurs when a virus spreads widely and rapidly among humans across multiple countries or continents.
3. Evaluate the options given: a. Spread to primates such as chimpanzees, b. Develop into a virus with a different host range, c. Become capable of human-to-human transmission, d. Become much more pathogenic.
4. Focus on option c: For a virus to cause a human pandemic, it must be able to spread efficiently from human to human. This is a key factor in pandemic potential.
5. Reflect on the implications: While increased pathogenicity (option d) could make the virus more dangerous, the ability to spread between humans (option c) is crucial for a pandemic.

Key Concepts

H5N1 Avian Flu Virus

The H5N1 avian flu virus is a subtype of the influenza virus that primarily infects birds but can occasionally infect humans. It is known for its high mortality rate in humans, though human infections are rare. Understanding its transmission and mutation potential is crucial for assessing pandemic risks.

Human-to-Human Transmission

Human-to-human transmission refers to the ability of a virus to spread directly between humans, which is a critical factor in the development of a pandemic. For a virus like H5N1 to cause a pandemic, it must acquire mutations that allow it to efficiently transmit between humans, beyond its original avian hosts.

Host Range

Host range is the spectrum of host species that a virus can infect. A change in host range, such as the ability of H5N1 to infect humans more effectively, can occur through genetic mutations or reassortment. This adaptation is essential for a virus to cross species barriers and potentially lead to widespread outbreaks.