Answer:
Bacteria and viruses are considered immortal because they reproduce and multiply very rapidly. Bacteria can divide into two identical daughter cells in as little as 20 minutes. Viruses can replicate by hijacking a host cell's metabolic machinery and creating multiple copies of themselves, which can then infect other cells. This rapid reproductive rate and lack of aging mechanisms means that bacteria and viruses can continue to reproduce indefinitely, making them "immortal" in a sense. However, bacteria and viruses can still be killed by antibiotics, antivirals, or host immune responses, so they are not truly immortal.