Mara Jade fighting coomb spores.
In normal beings, the spores broke down the victim's molecular structure and caused an agonizing death, usually within a few days. Of the first group that Nom Anor used the spores on, Mara Jade Skywalker was the only one who lived longer than a few weeks. The disease was non-communicable, as the coomb spores died along with the victim. Although an impressive range of species were known to have been vulnerable to its effects, with differing lengths of illness for each, it was not clear whether the Yuuzhan Vong themselves were susceptible to the toxin. The shlecho newt enjoyed eating coomb spores, and so could serve as a detector of them.
Nom Anor used these spores several times. Mara Jade Skywalker, then a Jedi Master, managed to hold off the effects with her abilities, and was eventually healed by Vergere's tears. Unfortunately for Nom Anor, the virus was non-communicable. The Yuuzhan Vong had planned to release the coomb spore into the galaxy to create a pandemic, but could not devise a way to make the spores self-replicating, thus making it impractical for large-scale usage.