The Infected á la L4D [3.5]

I haven't actually played the games (though I'm very interested and have read a lot about it), so feel free to correct anything that you find doesn't fit the original games. However, remember that I have to make a few modifications to make it more suitable for D&D:
1. I'm making some of them a little better in combat
2. I'm making the Infection harder to catch, with a difficult Fortitude save allowed, and a possible cure.

Infection mechanics

Spoiler

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To catch the infection, you need to either spend an extended amount of time in a location filled with Smoker gas, Boomer bile or Spitter acid, or somehow make close contact with infected materials (consuming Infected blood etc.) If any of these prerequisites is filled, a Fortitude save against the DC of 20 is made, once per day if caused by environment or once per contact.

If the Fortitude save is failed, one of the Infected templates is added. The exact template is determined mostly by DM fiat, though each template lists possible criteria for this choice.
The time it takes for the template to take effect is 1d6 days. Signs of transformation start showing when about half of the time has passed.
A cure can be created by carefully examining any carrier of the infection and making a Heal check against the DC of 25. Creating the cure takes 1 day for the first dose, and 1 hour for each additional dose. If the cure is applied before the transformation is complete, a new Fortitude save is allowed against the DC of 15, success meaning recovery. This means that additional care is usually required, and especially weak or unlucky individuals may not be cured. The cure may be used only once on a particular subject; if the save is failed, the Infection mutates to resist it.

The Hunter - -barely started- -

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The Hunter
Hunters are usually created when the Infection takes over an agile and acrobatic individual. They are the most common of the Special Infected, but they usually hunt alone. Hunters, as their name implies, are good at tracking their victims by their scents and can reach them with their great leaps and speed. Their behavior usually resembles that of a canine: they walk on all fours, make wolf-like sounds and attack by leaping on their victims and ripping them to pieces.

Sample Hunter
This humanoid, running on all fours, has sickly green skin and sharp claws and fangs. It growls like a dog and leaps towards you, baring its claws.
Here is an example of a Hunter, using a 1st-level commoner as the base creature.

Hunter 1st-Level Human Commoner
Medium Monstrous Humanoid (Augmented Humanoid)
Hit Dice:
Initiative:
Speed:
Armor Class:
Base Attack/Grapple:
Attack:
Full Attack:
Space/Reach:
Special Attacks:
Special Qualities:
Saves:
Abilities:
Skills:
Feats:
Environment:
Organization:
Challenge Rating:
Treasure:
Alignment:
Advancement:
Level Adjustment:

Creating a Hunter
"Hunter" is an acquired template that can be added to any living, corporeal humanoid or monstrous humanoid. A Hunter uses all the base creature's statistics and special abilities except as noted here.
Size and Type: The creature's type changes to monstrous humanoid. Size is unchanged. Recalculate base attack bonus and saves.
Hit Dice: Change racial HD to d8. Do not increase class HD.
Speed: The creature's base land speed increases by 10 ft.
Armor Class: Natural armor bonus increases by +1.
Attack: A Hunter has two claw attacks and a bite attack, the claws being the primary natural weapon. The claw attacks deal 1d6 damage for a Medium creature, and the bite deals 1d4 damage. For other sizes, use the table found on page 296 of the Monster Manual. A Hunter almost always uses its natural weapons, even if it would be able to use manufactured weapons.
Full Attack: A Hunter uses its both claw attacks and its bite attack when making a Full Attack.
Special Attacks: A Hunter gains the Pounce ability, allowing it to full attack after charging an opponent, as well as the Rake ability, allowing it to attack with its both claws while grappling, dealing 1d8 base damage as a Medium creature.
Special Qualities: A Hunter gains the Scent ability.
Abilities: +2 Str, +4 Dex, Cha -6, Int reduced to 2

Feel free to post ideas for the templates before I start making them.

The infection is odd, there are three kinds of people from what I understand:

1) People who can be infected.

2) People who are immune but can carry the disease to infect others anyways

3) People who are immune but don't carry the disease

From what I understand it's similar to most zombie based viruses, it's passed via fluids and possibly mildly airborne (proximity). It doesn't make you undead though (you probably know that) it's more like a rabies infection for humans.

edit: I look forward to seeing your interpretation

I know that stuff, but they're kind of hard to represent with mechanics. Of course, you can just decide who are immune or not, but you would basically have to make the party immune, as otherwise they'd be making Fortitude saves pretty much every round. That might work for a gritty game, but not so much for classic D&D.
This version makes the chance of infection more of a plot device.

EDIT: Added some details to how the infection happens.

The vast majority of the infected would simply become shamblers. I haven't played L4D much, but the special infected were clearly the vast minority. something like 1-5% became special infected. You could use a mechanic like vampires to determine if a specific target becomes an infected or a special infected, I.E, creatures with X HD or more become special infected, while everything else becomes traditional infected. Then you could do special infected based on ability scores. The smokers and spitters would be based off high dexterity, while boomers would be from those with high con.

Well, I could do that, but I think DM fiat (with criteria like the stuff you listed) works just fine for most games. Few DMs would mind playing a whole city of Hunters, anyway; Special Infected would be, well, Special.