Immortal pathogens can hide inside normal host cells (intracellular), and can hide inside or attached to the outside of other pathogens. Immortal pathogens live off the nutrients and energy provided by the host cell, and hijack the functions of the host cell. When immortal pathogens attach and combine with other pathogens, the immortal pathogens can reach and attack parts of the body reached by the host pathogens.
https://www.youtube.com/watch?v=WbG6mzYUnyU&feature=youtu.be&fbclid=IwAR07cSRiUzBpr1LyW6_XXDtifWuQI9z0N3RTdP37Hv9HXv6oyu1qvRAe1gg