What other virus enters but is not easily detected in osmosis Jones?

In "Osmosis Jones," the virus that enters but is not easily detected is the "Thrax" virus. Thrax is a deadly and highly contagious virus that poses a significant threat to the body’s immune system, especially as it evolves and adapts to evade detection by the immune cells. Unlike the more easily recognizable pathogens, Thrax's stealthy nature makes it a formidable adversary for the protagonist, Osmosis Jones, and his allies. The film highlights the challenges of identifying and combating such insidious threats within the human body.