Viruses and bacteria are not inherently harmful; in fact, a significant portion of them are highly beneficial to human survival.
For example, endogenous retroviruses are actually advantageous to the human body, serving as a crucial foundation for immune cells to produce antibodies.
There are also numerous retroviruses that scientists use as vectors for DNA recombination in modern medicine.
Historically, there was the cowpox virus, a pathogen that caused mild lesions in cattle. Early physicians utilized this relatively harmless virus to vaccinate humans and ultimately eradicate the deadly smallpox virus.
Beyond these beneficial viruses, there are countless beneficial bacteria. Strains like Bifidobacterium and Lactobacillus(Curd), as well as various yeasts, are essential for human digestive health and immune function, indirectly extending the human lifespan.
