The coomb spore was a singular type of microorganism, biologically engineered by Nom Anor, an operative of the Yuuzhan Vong. These spores were part of Nom Anor's scheme to be promoted to high prefect; he conceived the coomb, brollup, tegnest, and over a dozen other spore varieties to function as weapons with the potential to obliterate the New Jedi Order.
In ordinary lifeforms, the spores disintegrated the molecular makeup of the infected, resulting in an extremely painful death, typically within days. Mara Jade Skywalker was the sole survivor from the initial group subjected to the spores by Nom Anor who survived longer than a few weeks. Because the coomb spores perished alongside the victim, the affliction couldn't be spread. While a significant number of species were documented as susceptible to its effects, with varying durations of illness for each, it remained uncertain if the Yuuzhan Vong themselves were vulnerable to the toxin. The shlecho newt consumed coomb spores, thus they could be used to detect them.
On a number of occasions, Nom Anor deployed these spores. Mara Jade Skywalker, who at the time was a Jedi Master, was able to resist the effects using her inherent skills, and was ultimately cured by the tears of Vergere. The virus, unfortunately for Nom Anor, could not be transmitted. The Yuuzhan Vong had designs to unleash the coomb spore throughout the galaxy to instigate a pandemic, but they were unable to create a method for the spores to replicate independently, rendering it impractical for widespread deployment.