Random Disease Generator

Random Disease Generator

Diseases in RPGs are very much underused. How many times have you seen Resistant/Immunity to Disease? And how many times have you seen a disease actually come up in the game? The answers are probably “occasionally to often” and “never”. It’s understandable – diseases are passive threats that, depending on their severity, either mildly inconvenience you or force you to rest for a long time akin to crippling injuries. If one PC caught a debilitating disease, then everyone has to wait for him to recover, or the GM just goes “Okay, you find a suitable priest, pay him $100, and he cures you. Let’s keep going.” Diseases probably work much better if you’re using 1:1 time. But I’m writing not to advocate for 1:1 time (mostly), but to tackle an adjacent problem – GURPS has barely any diseases statted up. There is one in GURPS Basic Set, some in GURPS Bio-Tech, and a couple in, surprisingly, GURPS Tactical Shooting: Extreme Conditions. In addition to that, GURPS has a generic “infection” that sort of makes things better. I did write up some D&D and Pathfinder diseases in the past, but how do you decide on what disease does the character catch?

A few days ago, I opened the AD&D Dungeon Master’s Guide and found a bunch of tables for random disease and parasitic infestation generation on the first pages. To be honest, they look pretty damn good, and they inspired me to adapt them to GURPS. As always, I’m not doing a 1-to-1 conversion, because GURPS has a different degree of granularity, and I have to take into account more parameters than AD&D did. I hope this will be useful!

CONTAGION RULES

GURPS Basic Set has rules for contagion on page 443. They call for daily HT rolls if you enter a disease-ridden area or encounter a disease carrier. This implies that the GM already knows what the disease is, and whether the area is infected. AD&D has the exact same thing, but also tells you to make a monthly roll regardless of contact, or weekly rolls if in very hot weather, hot and moist weather, or filthy, crowded conditions in warm weather.

ACKS II Judge Journal also suggests making a contagion roll if the character endured seven consecutive days of frigid or rainy weather. Sounds sensible.

If you treat all areas as disease-ridden areas and enforce daily rolls, then the entire population will die out. A single monthly or weekly roll against HT should be sufficient to both provide a chance to catch a disease and prevent an instant pandemic. Apply the contagion modifiers on p. B443, but also do not forget the Hygiene modifier (GURPS City Stats, p. 6). However, since the virulence modifier of the disease is required, if you’re rolling a random disease, you have to do it before you make a contagion roll.

RANDOM DISEASE GENERATOR

Disease/Disorder Table

3d	Area of Body Affected	Occurrence (d8)		Severity (d8)
		Acute	Chronic	Mild	Severe	Terminal
3	Blood/blood forming organs	1-3	4-8	1-2	3-5	6-8
4	Bones	1	2-8	1	2-3	4-8
5	Urinary system	1-6	7-8	1-5	6-7	8
6	Cardiovascular-renal	1-3	4-8	1-2	3-4	5-8
7	Connective tissue	1	2-8	1	2-3	4-8
8	Eyes	1-7	8	1-5	6-7	8
9	Skin	1-5	6-8	1-5	6-7	8
10	Gastro-intestinal	1-6	7-8	1-5	6-7	8
11	Nose-throat	1-6	7-8	1-6	7-8	-
12	Respiratory system	1-6	7-8	1-5	6-7	8
13	Mucous membranes	1-7	8	1-6	7-8	-
14	Muscles	1-5	6-8	1-5	6-7	8
15	Joints	1-5	5-8	1-6	7-8	-
16	Ears	1-7	8	1-6	7	8
17	Generative organs	1-2	3-8	1-3	4-7	8
18	Brain/nervous system	1-6	7-8	1-2	3-5	6-8

The table intentionally uses 3d and not 1d, 1d, because the original table doesn’t have even chances of each affected organ being infected. Most commonly affected areas of the body are grouped closer to the 9-12 range, while the rarer ones were moved toward the extremes of the range.

Occurrence determines whether the disease is a single (acute) attack or whether the disease will recur periodically once contracted (chronic). An acute disease works like a regular disease and goes away once the victim recovers. A chronic disease does not go away so easily. After the victim recovers, roll 3d each month. On a roll of 15 or higher, the disease strikes again. On a 3-4, the disease goes away permanently. When a chronic disease is cured via the Healing advantage, the GM makes the usage roll in secret. If margin of success was 5 or higher, then the disease goes away permanently. If margin of success was lower, the disease goes away but may come back later as described above.

Severity refers to the seriousness of the disease, disorder, or parasitic infestation and determines the amount of damage, the number of daily cycles of said damage, and the virulence modifier (the penalty that is applied to HT rolls to negate damage. Roll on the appropriate table to determine these parameters.

Mild
1d	Damage per Cycle	Number of Daily Cycles	Virulence
1-2	1 toxic	5	-1d/2+1
3-4	1d-2 toxic	4
5-6	1d-1 toxic	3
Severe
1d	Damage per Cycle	Number of Daily Cycles	Virulence
1-2	1 toxic	12	-1d/2-1
3-4	1d-2 toxic	9
5-6	1d-1 toxic	6
Terminal
1d	Damage per Cycle	Number of Daily Cycles	Virulence
1	1 toxic	28	-1d/2-3
2-3	1d-2 toxic	16
4-5	1d-1 toxic	12
6	1d toxic	10

Difficulty of Treatment

Another parameter that has to be determined is the difficulty of treatment. This is relevant for the Healing advantage that can cure diseases and takes a modifier that depends on the difficulty of treatment. This modifier equals to 3 – 3d (thus, it ranges from +0 to -15).

In addition, roll an extra 1d. On a 1, the disease is drug-resistant, and ordinary medicine gives no bonus to recovery rolls.

Nature

Roll on the following table to determine the nature of the disease. This may be relevant because certain spells and abilities only affect diseases of a particular nature (for example, Cure Fungal Disease from GURPS Magic: Plant Spells). Magical diseases are not affected by Dispel Magic and require Remove Curse or an equivalent effect to be removed.

Nature of the Disease
1d	Nature
1-2	Bacterial
3	Viral
4	Parasitic
5	Fungal
6	Magical

Delay

This is the incubation period. Roll on the following table.

1d	Incubation Period
1-2	1 day
3	1d days
4	2d days
5	3d days
6	1d weeks

Contagion

Some diseases are mildly or highly contagious. Some of them are contagious even during their incubation period. But… what does this even mean? Of course, GURPS Basic Set introduces these terms but doesn’t even explain them. The actual explanation is hidden away on page 101 of GURPS Powers in the description of the Cyclic enhancement. This most obvious place, right? Anyway, roll on the following table.

1d	Contagion
1-2	Not contagious
3	Mildly contagious
4	Mildly contagious, including the incubation period
5	Highly contagious
6	Highly contagious, including the incubation period

Vector

This determines how the disease spreads.

1d	Vector
1-2	Blood
3	Contact
4	Digestive
5-6	Respiratory

Immunity and Susceptibility

Roll 1d. On 1-2, once you recover from the disease, you become permanently immune to it.

Roll another 1d. On a 1, the disease has differential susceptibility. Members of a given race, sex, or ethnicity receive a 1d-1d modifier on HT rolls against this disease. Determine the race/sex/ethnicity randomly according to your setting.

 

Disease Effects and Symptoms

Most diseases have detrimental effects in addition to cyclic damage, and many also have symptoms – effects that kick in when the victim loses a number of HP higher than a certain threshold – 1/3 HP, 1/2 HP, or 2/3 HP. These effects depend on what part of the body was affected, as was determined on the Disease/Disorder Table above. Some of the additional effects are intentionally made harsher to make diseases something more than just damage. If you don’t like that, simply ignore the permanent effects and treat everything as symptoms.

Trivia: Did you know that GURPS has a published ability to cure diseases for only specific organs? I’m talking about the spring spirit from GURPS Banestorm being able to heal diseases of blood and bladder only.

Blood/blood forming organs diseases cause a -2 penalty to ST and HT after the victim loses 1/3 of his HP to the disease. This penalty increases to -3 at 1/2 HP and -4 at 2/3 HP. In addition, when the victim passes each of these thresholds, make an additional HT roll against the disease with all the regular modifiers. Should the victim fail, he permanently loses 1 level of ST and/or HT (roll 1d: 1-2 is ST loss, 3-4 is HT loss, 5-6 is loss of both).

Bones diseases have the same effects as blood diseases (see above), but in addition to that, once the victim loses 2/3 HP to the disease, he must make an additional HT roll against the disease with all the regular modifiers. Should the victim fail, he permanently gains Vulnerability (Crushing Attacks, x2) [-30]. Even if he succeeds, this disadvantage persists as a symptom.

Brain/nervous system diseases may have very varied symptoms. Upon reaching each threshold, roll on the Skull Wounds Table on pages 138-139 of GURPS Martial Arts and make an additional HT roll against the disease with all the regular modifiers. If this roll is successful, the result is a symptom. If the roll fails, the effect is permanent.

Such diseases are particularly nasty if the victim has psionic powers. If that’s the case, each damage threshold also calls for a roll on the Optional Crippling Rules table from page 7 of GURPS Psionic Powers for one random psionic ability of the victim.

Cardiovascular-renal diseases may cause very severe effects. Upon reaching each threshold, roll on the table below and make an additional HT roll against the disease with all the regular modifiers. If this roll is successful, the result is a symptom. If the roll fails, the effect is permanent.

Cardiovascular-renal effects
1d, 1d	Effect
1-2, 1-2	-1 FP
1-2, 3-4	-2 FP
1-2, 5-6	-1 HT
3-4, 1-2	Easy to Kill 1
3-4, 3-4	Easy to Kill 2
3-4, 5-6	Unfit
5-6, 1-2	Very Unfit
5-6, 3-4	Restricted Diet (Very Common)
5-6, 5-6	Slow Healing 1

Connective tissue diseases (such as leprosy) cause the victim to permanently lose 1 ST, 1 HT, and one level of Appearance each month. Thus, only disorders with a high number of cycles can cause this loss. This cannot bring Appearance below Hideous.

Ear diseases have permanent effects only if they have terminal severity. Such diseases cause permanent Hard of Hearing upon the victim losing 2/3 of HP to it. If the victim already has Hard of Hearing, he becomes deaf instead.

Eye diseases have permanent effects only if they have terminal severity. Such diseases cause permanent blindness in one eye upon the victim losing 2/3 of HP to it (equivalent to One Eye disadvantage for two-eyed beings). If the victim already has One Eye, he becomes blind instead.

Gastro-intestinal problems of severe or terminal severity cause a -1 penalty to ST and HT upon the victim losing 1/2 HP to the disease. Terminal ones require an additional HT roll against the disease upon the victim losing 2/3 HP to the disease, with failure indicating a permanent loss of 1 HT.

Generative organ disorders cause no particular problems except spread of infection but also give the victim the Social Disease disadvantage.

Joint diseases of acute nature decease the victim’s DX by 1 upon losing 1/2 HP and by 2 upon losing 2/3 HP. Chronic joint diseases are much more dangerous. Upon losing 1/2 HP, the victim has to make an additional HT roll against the disease. If he loses, he permanently gains the Chronic Pain disadvantage (p. B126). Mild chronic diseases cause Chronic Pain (Mild), severe chronic diseases cause Chronic Pain (Severe), and terminal chronic diseases give Chronic Pain (Agonizing). Determined interval and frequency of appearance randomly.

Mucous membrane diseases of chronic nature that are severe or terminal reduce HT by 1 when victim loses 1/2 HP to the disease. An additional HT roll against the disease is made when the subject loses 2/3 HP – on a failure, the loss becomes permanent.

Muscle diseases cause a -1 penalty to ST when the victim loses 1/3 HP to the disease. This penalty increase to -2 when the victim loses 1/2 HP, and -4 when the victim loses 2/3 HP. When the victim loses 1/2 HP to the disease, he also has a -1 penalty to DX. Severe and terminal diseases call for an additional HT roll against the disease upon losing 1/2 HP and 2/3 HP to avoid permanent loss of 1 ST and 1 DX.

Nose-throat diseases cause moderate pain (p. B428) when the victim loses 1/2 HP to the disease. Severe or terminal chronic diseases require the victim to make an additional HT roll against the disease upon losing 2/3 HP to it to avoid permanently gaining No Sense of Smell/Taste.

Respiratory diseases cause coughing (p. B428) when the victim loses 1/2 HP to the disease. Severe or terminal chronic diseases require the victim to make an additional HT roll against the disease upon losing 2/3 HP to it to avoid permanently losing 1 HT.

Skin diseases of severe or terminal nature drop the victim’s Appearance by one level (but not below Hideous) when he loses 2/3 HP to the disease. For chronic diseases, the victim has to make an additional HT roll against the disease upon losing 2/3 HP to it to avoid permanently losing one level of Appearance.

Urinary system diseases of chronic, severe or terminal nature cause a -1 penalty to HT and DX when the victim loses 1/2 HP to the disease. Upon losing 2/3 HP to such disease, the victim must make an additional HT roll to avoid permanently losing 1 HT.