I was looking at the disease rules and decided they are to structured for such a broad category of hazards. I suggest the following changes:

Strength	Modifiers
Marginal	-3 or -2
Ordinary	-1 to +1
Good	+2 or +3
Amazing	+4 or more

I would also eliminate the set incubation periods and make one for each disease (e.g. the neocold takes 3d4 days to incubate). Here is a waterborne disease of my own creation as well as some other diseases.:

Name          Strength          Incubation period

The Bends          Good (+2)          2d4 days
The bends (a misnomer) is a freshwater bacteria. It is always found in stagnate water and anyone drinking from infected water has a 35% chance of ingesting some of the bacteria. Its waste causes cramps and dizziness.

The Thirst          Ordinary (+1)          d4 days
This protozoan gains its oxygen form the water it dwells in. When it causes an infection, the infected organism has its blood/sap dehydrated and acidified. If the infected organism drinks twice the normal amount of clean water per day, all CON feat checks due to the disease are at a -2 step bonus.

Neo-Anthrax          Amazing (+4)          3d4 weeks
This extremely altered disease was used against the Invaders (and thus works on PSHs). It kills by destroying the blood vessels.

Whip Lash          Ordinary (+0)          2d4 days
This bacteria attacks muscle tissue. It is called whip lash because of the neck pains it usually inflicts.

Anthracnose          Good (+2)          d2 months
This plant disease attacks phloem- the conductive tissue that moves sap. It causes darkening of leaf veins and a general weak feeling.

Fire Blight          Amazing (+4)          d3 weeks
This plant disease is a devastating bacterial infection. It causes leaf and twig loss and eventually whole branches die.

Pythium          Good (+3)          d4 months
This plant disease is feared by all plants. It causes root rot. Even if the plant survives, it may need to root for longer periods until the roots heal and regrow.

Neocold          Ordinary (0)          3d4 days
Many of the cold viruses were mutated during and after the Cataclysm. Most neocolds just cause the victim misery for a few days, but a few can kill.

Lyx          Amazing (+4)          3d4 weeks
The lyx is a protozoan that uses metals as the terminal electron acceptor instead of oxygen. It puts the reduced metal on the wall of the blood vessel it inhabits. When the victim dies, up to $300 worth of metals can be recovered from his body- more if saltwater was consumed while the disease lived within him.

Plague          Good (+3)          d4 hours- 1 week
This infamous disease was the one that killed off 1/3 to 1/2 the population of Europe. If it affects the lymph system, it is the bubonic plague and has a 1week incubation period. If it affects the lungs, it is called the pneumonic plague and has a d3 days incubation period. If it affects the blood, it is called the septicemic plague and has a d4 hours incubation period.