How can an infected creature weaponize its inhaled and injury diseases?

Question

The Dungeon Master's Guide says on pages 292-3 that diseases can typically infect folks 4 ways:

• consumed from eating or drinking tainted matter,
• contact from touching an item smeared with tainted matter,
• inhaled which goes undefined, and
• injury from a contaminated attack (e.g. the slam attack of a mummy)

The 1st-level Sor/Wiz spell suspend disease [abjur] (Book of Vile Darkness 106) for 24 hours prevents 1 touched creature's

disease [that's] already infecting the subject from harming him for that day. The disease is in no way cured, and the subject cannot make a save to throw off the disease.¹

Combined, this means a creature infected with a disease spread via the contact or consumed methods can ignore these diseases' effects yet spread these diseases with relative ease (e.g. the creature infected with the contact-infection disease the shakes (DMG 292) could smear his own tainted matter on his weapons²—maybe, as a house rule, in much the same manner as a poison—so a foe struck by the weapon risks contracting the disease, the creature could get a job in the elf cafeteria and infect the elves with the ingested-infection disease blinding sickness by spitting in the twig soup or cooshee pudding³). In other words, these diseases pretty much weaponize themselves.

But I'm still struggling to weaponize diseases with the inhaled and injury infection methods.

1. Were rules ever provided for what, exactly, that inhaled infection method means? A radius, perhaps? A counter beyond divine health or other disease immunity, like an air mask or something?

2. When a creature's infected with an injury disease, can the creature also spread that disease by injuring a foe? By injuring a foe with a natural weapon? By injuring a foe with the same kind of natural weapon that delivered the disease? At all?

   Example
   Al's contracted ghoul fever and can and does cast the spell suspend disease so he won't ghoul out… ghoul up… ghoulify… become a ghoul. As a pretty evil dude, he wants to start the ghoulpocalypse by giving those thorp-dwelling commoners ghoul fever. To do so, must Al stab folks with his dagger to force commoners to make Fortitude saving throws to avoid being infected with ghoul fever? Can he cast the 1st-level Drd spell beast claws [trans] (SpC 25) and infect commoners with ghoul fever by using his claw attack?⁴ As ghoul fever's delivered via a bite must Al cast the 1st-level Drd spell aspect of the wolf [trans] (SpC 16) to infect commoners with ghoul fever via the wolf's bite attack? Or is poor Al stuck with his ghoul fever infection, unable to spread it until he succumbs to it and himself becomes a ghoul?

(What I'd really like for diseases is an official spell like the 5th-level Clr spell spit poison [trans] (Dragon #304 37-38) which permits the caster to make a ranged touch attack that, if successful, poisons the foe with all the poisons coursing through the caster, but I've not found such a spell.)

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¹ The similar 1st-level Clr spell delay disease [conj] (SpC 63) doesn't supersede the spell suspend disease according to the section Renamed Spells (5-6), making suspend, if available, the superior choice as suspend affects supernatural diseases.
² I was thinking he'd spit on his weapon. You might be thinking something else. Ew.
³ Relax! It's only shaped like a cooshee.
⁴ Yeah, Al's a druid. He helped the thorp with their planting, and now it's time to preserve the balance!

Answer 1

It is pathfinder, but you may find it useful. I spent the first half of a campaign as a Plague Bringer (racial archetype of an alchemist), where one of the class abilities is to effectively infect yourself with an active disease, but no drawbacks. I'm not saying use the class, but some of the mechanics of the class abilities cover questions you have.

Injury

Injury, by my definition, generally means bodily fluids of person A gets in bloodstream (or equivalent) of person B. This is backed up by Pazio's description of one of the class abilities of the Plague Bringer, which includes a description of coating a weapon to cause infection:

As a standard action, the plague bringer can infect a weapon with this sickness (typically by licking it or wiping his blood or pus on it). The disease on the weapon works like a poisoned weapon, except the source is a disease instead of a poison (so a dwarf's resistance to poison does not apply).

The page makes no mention of natural attacks though, which implies that a natural attack alone is insufficient to require a fort save. Note that teeth are, by default, covered in spit, so a successful bite should inflict a fort save¹. If your druid is nervous and chews his claws, then that might also work, but that's up to the DM.

As to spreading a disease that you have, I would give an easy yes to any non-magical disease. If someone infected couldn't spread the disease, it would quickly die out. Supernatural diseases though are a different story, and I would defer to @Ruut in that case.

Inhalation

Immunity wise, anything that cleans air should work, for example Dance of the Unicorn (Druid 5th level spell):

You surround yourself with a purifying, swirling mist with a radius of 5 feet per caster level that washes the air clean of smoke dust, and poisons. Nonmagical contaminants, including inhaled poisons, are automatically negated within the cloud.

But on the infection side, I can't find anything that seems to cover spreading the disease. Doing it purposefully seems especially hard. You could cough on the person, which (inventing this on the fly here, but it seems to work) would be a improvised(so it has the improvised weapon debuff) touch (unless they had something covering their mouth/nose) attack with a five foot cone.

Alternatively, you could take your coughed up phlegm/spit/blood and aerolize it like plague bomb (another pathfinder item, apologies):

The effects of the smoke created by an alchemist’s bomb duplicates the effects of contagion instead of fog cloud, filling an area equal to twice the bomb’s splash area for 1 round per level.

Really, I think that if you are a carrier for a inhalation disease, I would homerule it as a passive effect that people who spend time near you (including PC's) need to make a fort save every so often, but every X number of times they beat it, the time period between saves increases. I'd go with an exponential increase: every minute, then hour, then day, week, month, etc. If they catch the disease, but are cured, it should still count towards resistance towards that disease (if not near total immunity).

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Notes

1. For example, Mindwin notes in the comments that a human bite is highly prone to infection, see this, especially the part about clenched-fist injuries, which you get from the skin of a fist breaking as it strikes teeth.