Final answer:
Bird Flu (H₅N₁) is caused by an Orthomyxovirus, which is a group that includes Influenza viruses A, B, and C. The Influenza A virus has various subtypes, including H₅N₁, which is associated with Bird Flu.
Step-by-step explanation:
The causative agent of Bird Flu, specifically the H₅N₁ strain, is an Orthomyxovirus. Influenza viruses, which include Influenza A, B, and C, are all part of the Orthomyxoviridae family. Among these, the Influenza A virus is known for its subtypes, which are characterized by different hemagglutinin (H) and neuraminidase (N) proteins. There are 18 known H subtypes and 11 N subtypes, leading to various combinations, with H5N1 being one notable subtype that has been associated with Bird Flu outbreaks in humans. The H₅N₁ virus is highly pathogenic and has been recognized as a potential threat for a pandemic, though it primarily spreads from birds to humans and has not yet mutated to a form that transmits easily between humans.