As promised, wheat extract is used to make what appears to be a permanent cure for the Lung Spore disease. If you have at least one wheat extract in your inventory, at the chemistry laboratory you will get the option to make Lung Spore Cure Treatment.
The formula for making the cure is:
With those items, you select the option on the lab to mix the cure. You will get this message: "You dump all of the water into the cistern, add emeralds and wheat extract, and mix it up. The color of the water changes to a strange greenish amber." At this point, you have the option to take from the lab 1000 Treatment: Lung Spore (Cure), which is 1000 doses of the cure. To take the cure, click yourself and select skills/consume from your menu.
If you take the cure when you are well, you will get the following message: "You quaff the greenish-amber liquid. It tastes somewhat like beer, or bread, but much lighter. You don't feel any different." In experimenting, taking the cure when well provides no immunity. You will still be able to get sick if you spend sufficient time in close proximity to a sick person.
Taking the cure when sick gives this message: "You quaff the greenish-amber liquid. It tastes somewhat like beer, or bread, but much lighter. You feel the sickness leave your body." From further experimentation, taking the cure when sick does appear to provide sustained immunity. Of course, we will know for sure as more time elapses. But thus far, this does appear to be a permanent cure.
Permanent cures so far have been distributed to Sinai, Seven Lakes, Karnak, and Kush. Contact people in those locales are: Hasani, Ping, Sqatsi, Cathy ( not cure in stock) chat hasani , and Tat2mikki. Of course, you don't have to reside in those particular regions to get cures from these people. Any of them are happy to provide cures to anyone needing a cure. You may also want to check with your local public works guilds, as some of them also have cures available.