Final answer:
Flu viruses like bird flu and swine flu have the potential to cause a pandemic in the future if they undergo further mutations to become more transmissible among humans.
Step-by-step explanation:
The possibility of a future pandemic caused by a bird flu or swine flu strain cannot be ruled out, as flu viruses have the ability to evolve rapidly. For example, the H5N1 avian flu virus has the potential to cause a pandemic if it undergoes further mutations that allow it to spread easily among humans.
Similarly, swine flu strains like H1N1 have caused previous pandemics. However, it is important to note that the emergence of a pandemic depends on various factors such as the virulence and transmissibility of the virus.