Crawl Out Through the Fallout (Radiation in Twilight: 2000)

Like a disease, radiation is an "unseen" threat in the Twilight World. Unlike a disease, which is amenable to medical intervention, radiation sickness is not particularly treatable apart from providing supportive care and a character's chance of surviving is only dependent on their CON score and their accumulated exposure. 

View of Chernobyl from a ruined window(sepia-tone modified image from this VICE article)

Radiation is a mid-late threat as it takes time for the risk of radiation sickness to build up through repeat exposure but unlike other threats that can be resolved or reset, the threat of radiation worsens over time the more exposure a character has during the game and there's no way to decrease this risk through medical treatment.

I'm Radioactive! - Radiation Exposure 

I'm waking up to ash and dust
I wipe my brow and I sweat my rust
I'm breathing in the chemicals
I'm breaking in, shaping up, then checking out on the prison bus
This is it, the apocalypse

Whoa... 

- "Radioactive", Imagine Dragons 

The rules for radiation and the potential for radiation sickness are given on pages 242-243 of the v2.2 corebook (although as each page has a half-page image, the rules really only cover one page of dense text). Although potentially radiation sickness could be considered a "disease", the rules use separate mechanics, adding another "mini-game" to the overall system.

Starting rads are calculated according to pages 23-24. For military characters, this is No. Terms x2 x D6 (effective maximum 84 rads for 7 terms) and civilian characters 1D6 x 1D10 (max 60 rads). A high score puts starting characters at risk of radiation sickness with any further exposure but otherwise, most characters will not have any issues until more than an hour of exposure to a crater or their second and subsequent exposures.

Radiation Illness CON modifiers
(T2k v2.2 corebook page 244)

Rads less than 50 have no effect, anything greater requires a CON check on D10 multiplied by a modifier on the table on page 244 depending on the character's *total* rads accumulated:

• Slight illness is a risk at 50+ rads and becomes automatic at 400+ rads
• Serious illness is a risk at 100+ rads and becomes automatic at 600+ rads 
• Death is a risk at 300+ rads and becomes automatic at 800+ rads 

Fortunately, radiation is relatively easily avoided compared to disease - the main source is impact craters usually found in the ruins of larger cities or occasionally during a travel Encounter (a 1 in 10 chance if an Item encounter is triggered except in cantonment or disputed regions). As only a few years have passed since the nuclear exchange, most craters will be readily identifiable even if partly eroded although this may be more difficult in urban ruins also damaged by conventional explosives.

The radioactive areas associated with craters are larger than the visible crater however and range from 3/4 km across to about 1.5km across. Other sources of radiation eg leaking reactor cores or radioactive waste are not explained except for a nuclear detonation. A Geiger counter confirms the presence of radiation, allowing exposure to be avoided. The game suggests that a lack of animals or vegetation as a ready clue - this is not strictly correct as plants can actually tolerate a level of radiation. 

At a rad accumulation rate of 1D6 per minute in a crater area, on average an hour of exposure without protection exposes a starting character to ~210 rads (60 minutes x 3.5 rads on average), running the risk of slight illness *and* serious illness, but not the risk of death unless they've had additional exposures already. This assumes you don't roll 60D6 (one dice for every minute) or multiply a single D6 roll by 60 which seems potentially disastrous (max 360 rads from one-hour exposure).

Higher and/or longer periods of exposure have the following averaged effects:

• 2 hours (~420 rads) automatically causes slight illness and runs the risk of death. 
• 3 hours (~630 rads) automatically causes serious illness.
• 4 hours spent in a crater without protection (~840 rads) is certain death. 

A nuclear detonation (~6000 rads) is noted to be immediately fatal.

A character travelling in an "enclosed" vehicle accumulates 1/10th the rads, a radiologically "shielded" vehicle only 1/100th the rads. A MOPP suit probably provides protection as a "shielded" vehicle but it's not explicitly stated in the corebook. It is possible to survive the radiation effect of a nuclear blast in an enclosed vehicle if not directly exposed to the shockwave and blast, although the crew will suffer serious illness at least as the dose is 600 rads (only 60 rads in a "shielded" vehicle).

Radiation Sickness

Once a character has 50+ rads, if exposed to significant to radiation the character must make up to 3 CON based checks (one each for death, serious and slight illness in order)), *every* time they are exposed to radiation. Unlike diseases, there are no modifiers that affect this check, the only way to reduce the risk is to avoid or reduce exposure in the first place. An exposed character only has to check once per day - this seems to just be a mechanical simplification for the game as it's possible to be exposed more than once several hours apart from different sources.

Radiation Exposure Infographic
(Mayo Clinic website via raytodd.blog)

There is no Medical: Diagnosis check involved in diagnosis although some of the symptoms (nausea, vomiting, headache) could be mistaken for infectious disease and supportive care, supervised by a character with that skill, is needed to reduce the period of incapacitation (see below).

Death is always checked for first at accumulated 300+ rads - failure of the CON check results in slight illness within 1D6 hours (see below), then serious illness 2D6 days afterwards (1D6 days if 300+ rad exposure) with incapacitation lasting 1D6 days or more during which the character *dies*. No treatment ameliorates this, making radiation one of the few "auto-kill" threats in the game.

Slight illness occurs within 1D6 hours of significant exposure and results in *halving* of STR, AGL and INT for a day (2 days if rads exposure is 600+). This is debilitating but not incapacitating and oddly does not affect CON or increase Fatigue like a disease would, nor does it make the character more prone to a superadded infection.

Serious illness has a delayed onset of 2D6 days (1D6 if rad exposure 300+) and incapacitates the character for at least 1D6 days, followed by a "general" illness period with the same effects as slight illness above that last 1D6 weeks. The only "medical" treatment of serious illnesss is essentially supportive and considered equivalent to the same amount of time as for two serious wounds (as per page 211):

"First, the caregiver must spend half an hour per wound level, per body area damaged, per day, tending to the wounds... Second, once per day the caregiver must pass an Average check of his or her Medical asset. If no medical equipment is available (a doctor's kit is minimum), then the task check becomes Difficult. Failure means that one of the two days' worth of time to be saved was lost. In other words, if the task is failed one day during the treatment period, only one day is saved from the normal healing time. If the task is failed twice, no days are saved. Note that failing the task a third time (or more) does not add time to the basic healing rate unless a Catastrophic Failure Is rolled on this third check (or beyond)."

This calculates out to two serious wounds (2 x 3 x 30 minutes, 3 hours) or almost a whole 4 hour period of medical care per day, provided medical equipment is available. Lack of this supportive care results in a longer duration of serious illness by up to 3 days (1 extra day per 2 days of incapacitation). Specifics of this supportive care are not given other than supervision by a character with a Medical asset, presumably Diagnosis as this is similarly used for disease.

Note:  it seems an oversight that serious illness at least does not inflict Fatigue levels or increase infection risk by reducing CON to half as lethargy, blood system dysfunction and impaired immune function are characteristic of radiation sickness, but it's possible this is to avoid the potentially lethal "double-hit" combination of radiation and disease affecting the same character at once. A Fatigue level of two in the post recovery "general illness" phase similar to other major diseases would seem a reasonable optional rule.

"General" illness refers to the recovery period following serious illness and is similar to the debility phase but confusingly named - an example of how the two sub-systems vary and create separate "mini-games" within the overall rules and add to the complexity.

Option: Chelation Therapies

Note: this optional detail is added after the initial post's publication thanks to "swaghauler" - I think it adds to the overall canon rules without affecting the role of radiation in the game.

"The one thing that GDW did not discuss in the initial publication is the methods of treating Radiation or even Heavy Metal exposure in order to reduce the RADS absorbed by the exposure. In their defense, this was not available to the public at large in the '80s when they were writing the game.

Potassium Iodide Tablets: These can be taken shortly after exposure (up to 1 hour) in order to "bind" some of the radioactive particles and pass them from the body through the kidneys. This will remove 1D6 rads from the exposure total.  

Prussian Blue Treatment: I have only seen this in injectable form but it may be available in an oral form. Like PI tablets, this will bind to various radioactive elements and allow you to pass those rads by urination. It will reduce exposure by 2D6 rads.

DTPA (Diethylene Triamine Pentaacentic Acid): I don't know if this is oral or injectable but it will bind to radioactive metals in the system and can reduce the RADS absorbed by 1D6. It can also be used to treat heavy metal poisoning. It provides a bonus of 1 to the CON checks (see my Food Contamination Table in the Storing Food thread).

Lithium Dioxide: An injection that can help one fight off heavy metal poisoning just like DTPA above.

I have no idea what the Availability or Costs of these meds should be. Input is obviously welcome."

- Post by "swaghauler", Juhulin Forums April 2019

Conclusions

Overall, from my reading, the rules for radiation sickness seem to model real-life "acute radiation syndrome" reasonably well from a mechanics perspective and the difference in mechanics to disease seems justifiable - radiation is an insidious but avoidable threat that builds in lethality over time but has little chance of medical intervention. 

As a scenario driver, radiation is useful more as a negative influence to prompt the player group to avoid a particular area, at least until they have obtained the appropriate equipment and/or vehicles to negotiate or significantly reduce the risk. The lack of treatment and the inevitable increase in debility through accumulated exposure provides a different tempo and from a campaign perspective, it's more relevant mid-late game and likely irrelevant in the early phases of a campaign. 

So if fuel and then food dominate the early phase of a default Polish campaign pre-Winter and armed conflict and disease are otherwise constant threats, in my mind radiation looms as a potential consequence of a long-term stay in a landscape littered with nuclear craters.

Bring Out Your Dead (Disease in Twilight: 2000)

This is another in the series of posts exploring the various "mini-game" mechanics within the Twilight: 2000 v2.2 rule-set, this time the "unseen" threat of diseases - a threat that can't be solved with bullets alone. I suspect diseases are underutilised in most campaigns, possibly because of their threat to player agency and the usual emphasis on combat as conflict resolution.

Like a lot of the game mechanics, the rules for diseases are based on a  complex combination of different dice rolls and sub-systems which can be difficult to appreciate the impact of without working through examples and/or using the rules in extended play.

Plague: Carting the Dead, by J. Moynet (Wikki Commons)

The White Horse: Disease

"The horseman on the white horse was clad in a showy and barbarous attire. [...] While his horse continued galloping, he was bending his bow in order to spread pestilence abroad. At his back swung the brass quiver filled with poisoned arrows, containing the germs of all diseases." 

- Vicente Blasco Ibáñez, "the Four Horsemen of the Apocalypse"

Disease is considered an important "scenario generator" in the game, likely more so than many RPGs - although the nuclear exchange and war inflicted heavy casualties, it was the resultant infrastructure breakdown and outbreaks of disease that dropped the global population to 50% or less in some areas. In the resulting Twilight World, the threat of disease remains ever present and is suggested to drive stories other than just straight "shoot and loot" conflict.

By my calculations, a disease very commonly affects settlements the group may encounter - almost 1 in 4 settlements if using the random crisis recommendation (see comment below).

Disease rules are given on pages 244-245 of the v2.2 corebook, with specific details of the various disease on the following two pages. The whole "mini-game" mechanics for disease are particularly complex, even when compared to other "non-combat" threats such as running out of fuel, vehicle breakdowns, starvation, fatigue, and radiation.

Other than this main section the only references are in the Biology (people/water), Medical: Diagnosis (draft animal/people/water), Survival (water), and Tracking (wild animal) skill descriptions of the difficulty levels for detecting disease.

Medical: Diagnosis (EDU) overall is the most relevant skill, not only because it aids with recognising contamination across animals, people and water but also as it is used to diagnose the correct disease and modifies the recovery roll for the infected character. As Medical is a "cascade" skill, characters with Medical: Trauma Aid or Surgery have some skill with Medical: Diagnosis.

Catching a Disease

There are three ways to contract a disease:

• People encounter (Biology or Medical: Diagnosis check)
• Settlement (includes merchants, army groups; possibly marauders, hunters)
• Encampment (includes refugees, stragglers; possibly marauders, hunters)

• Animal encounter  
• Draft animal (Biology or Medical: Diagnosis)
• Wild animal (Tracking check while on the trail)

• Drinking contaminated water/food (Biology, Medical: Diagnosis  or Survival check)

Note: it's not explicit in the actual Encounter section but the implication is that Disease should be checked for *every* relevant encounter eg Animal, Group, or Settlement. The risk of a particular people or animal encounter (or water) carrying a disease is given on the various tables on page 274 of the corebook.

Disease Frequency and Type Tables 
(Twilight: 2000 v2.2, page 274)

People: contracting a disease is dependent on the sanitary conditions - "settlement" reflects groups that practice good sanitation and so includes merchants, army groups and possibly more organised marauders and hunters. "Encampment" reflects less sanitary conditions and applies also to refugess, stragglers and some marauder / hunter groups. The base chance for "settlement" is 11+ on 2D6 or 8.34% (1 in 12) and for "encampment" is 16.67% (1 in 6).

Note: if using the Settlement Crisis suggestions, any settlement that rolls of "9" (Epidemic, doctor needed) or "10" (Disease, medicine needed) indicates a potential risk of contracting disease above and beyond the tables. So even if there's only about a 10% chance on average of disease for a given settlement/encampment, there's still a 20% chance (1 in 5) that it's been affected by disease in some way, further underlying the frequency of disease as a potential threat. Taken together, this is a 28% chance (roughly 1 in 4) of disease (recent, current or imminent) being an issue for any given settlement.

Animal: the base chance of an animal carrying a disease is 5.56% (1 in 20).

Water: this refers to water away from settlements including rivers, lakes, streams, springs, abandoned wells. The risk is the same as for animals ie. 5.56% (1 in 20). If detected the contaminated water can be avoided or boiled to avoid exposure - this would seem to be sensible and standard practice for any military trained characters with Survival skill.

Detecting Disease

Detecting a disease is an AVG difficult skill check (x2 Attr+Skill), with the skill applicable depending on the encounter as noted above:

• Biology (EDU) is used for animals, people and water
• Medical: Diagnosis (EDU) is used for draft animals, people and water
• Survival (INT) is used for water
• Tracking (INT) is used for wild animals

Medical: Diagnosis (or Biology) is the most useful skill for detection, and although Biology is also used to manufacture antibiotics, Medical (any) has much broader use. Tracking for wild animals seems to refer to identifying a diseased animal before the encounter in order to completely avoid them, I'd consider that once encountered Biology and Medicine: Diagnosis could be used instead.

A character with at least a "Novice" level Asset (Attribute + Skill = 9) in one of the relevant skills above therefore has a 90% chance of identifying a disease, with Experienced or higher level characters with the correct Asset capable of *automatically* detecting disease.

Even an unskilled character with a high EDU or INT Attribute level (8+ for example) has a reasonable rate of success at 40% (difficulty level is doubled from AVG to DIFF as unskilled).

Risk of Infection

Encountering a contaminated individual, animal or water alone is not enough to risk infection depending on how the disease is spread, it depends on whether they are exposed to one of it's modes of transmission (page 245):

The Referee should consult the description of the disease to determine how it is spread and compare this with the group's particular vulnerabilities. A disease spread by tainted food is not spread to those who don't eat the food, and one spread by contact doesn't affect those who do not make contact with the victim. A disease spread through the air places all characters within range at risk. 

As noted above, boiling contaminated water before drinking removes the risk of infeciton, even if the presence of disease is not detected - this applies to dysentery, cholera, hepatitis-A, typhoid fever, and possibly minor waterborne diseases. Only dysentery and typhoid are normally contracted from "wild" water sources however, the other waterborne diseases result from encampments/settlements.

Resisting infection is an AVG Constitution check (2x Attribute) on d20, with the target score modified as follows based on how vulnerable the character is and the disease's virulence:

• -1 for each Fatigue level (includes those from starvation)
• -x depending on the disease's "Infection Number" (up to 6)

For most unfatigued characters with an average CON of 5 for a target of 10 or less, the base risk is therefore 50% ie 50% chance of catching the disease if exposed. As most diseases have an "Infection Number" of at least 3, this reduces the target to 7 and gives the character a 65% (2 in 3) risk of contracting the disease. More virulent diseases (those with Infection Numbers of 5+ like Cholera, Pneumonia and Pneumonic Plague) increase this risk to 75% (3 in 4) for an average character.

Characters with weak base health such as a CON score of 2 or 3, have a high susceptibility to disease as their base chance of avoiding contracting infection is 30% or less, before the modification from the disease's Infection score! 

It's easy to see how Fatigue and starvation can rapidly lead to infection even in normally strong fit characters - as each Fatigue level reduces CON by 1 *and* reduces the Asset by another -1, the risk of infection rapidly escalates and easily spreads in communities or groups of soldiers without food even if they start with good health (reflected by a high CON score of 8+).

Note: the example on page 245 using Monk is wrong, his target should be 12-2-3 or 7 as the AVG difficulty should double his CON of 6 - the worked example uses a base of 5. So if he rolled a 4 on d20 he would have actually avoided contracting the disease. 

Diagnosis & Misdiagnosis

Image: Snook 8 / Deviant Art
(Header for this article on ISIS and Ebola)

Overall, the specifics of the various diseases as presented in dense blocks of text are difficult to understand, so I've collated all the cramped text information into a table to analyze further:

Summary Disease Diagnosis table
(derived from pages 246-247 T2k v2.2 corebook)

Looking at the "Diagnosis" table, food/water contamination seem the most common mode of transmission, whereas typhus, rabies and bubonic plague are more specific and readily avoidable.  Only pneumonia and pneumonic plague are spread through the airborne route.

Pneumonic plague is the most virulent (Infection Score of 6) and the two most difficult to diagnose diseases are hepatitis A and typhoid fever, although the latter cannot be mistaken for a minor disease.

Diagnosis in phase I of the disease is a Medical: Diagnosis check; this is one step easier (FOR becomes DIFF, DIFF becomes AVG, AVG becomes EASY) in phase 2 of the disease. Most diseases can be misdiagnosed as a minor disease leading to ineffective treatment and potential dire results.

Effects, Treatment, and Death or Recovery

This is where it becomes complex. Again I think constructing a table helps for this section.

Each disease has an incubation phase (no effect / unable to diagnose), a phase 1 (harder to diagnose but easier to recover from) and a phase 2 (easy to diagnose but more severe, treatment *half* as effective and harder to recover from). Treatment begun earlier works better, so diagnosing the disease correctly early makes a significant difference.

Recovery rolls are a D10 that must exceed the "base recovery" number.

This is modified by:

• + CON score (average +5, max +10)
• + Medical: Diagnosis of the treating character (effectively up to +5) 
• + bonuses from correct treatment (assumes correct diagnosis, up to +8)
• -1 for inadequate food
• -1 for inadequate shelter 

All the diseases have a "base recovery" number of 18 or more - assuming adequate food and shelter, a character with an average CON of 5 and an average roll of 5 or 6 still needs the benefit of the treating character's Medical: Diagnosis skill (effective max 5) and treatment to have a chance of recovery.

If a character fails a recovery roll during phase 2 they have a risk of actually *dying*. 

If the character does not die they suffer debility (modified by the recovery roll success or failure).

Summary Disease Treatment & Recovery table
(derived from pages 246-247 T2k v2.2 corebook)

Comments on Specific Diseases

Rabies particularly seems quite insidious and lethal - although potentially readily avoided, it has a long incubation period of *weeks* and it's "base recovery" is 26 with a death probability of 100% ie automatic death if recovery fails. Although the 14-day DE vaccine provides a +8 modifier, the D10 + CON roll still has a target of 18, relying heavily on the treating character's Medical: Diagnosis skill. Without the specific treatment (the rare vaccine), an infected character with CON 10 and an excellent roll of 10 on the D10 needs to be treated by a character with a Medical: Diagnosis skill of 8+. The prolonged debility period of 20 weeks is the longest of all the diseases presented.

The two plagues (bubonic and pneumonic) are also essentially lethal on a failed recovery roll with extended debility periods of 15 weeks each. The next most deadly is actually food poisoning, with a death probability of 50% and a difficult recovery roll although if a character survives, their debility period is relatively short at 2 weeks.

The other disease (including minor diseases) are rarely lethal and easier to recover from, with debility periods of 6 weeks or less and easier to source treatment options.

Tuberculosis is a notable omission as it's apparently very common in war scenarios. Although perhaps more insidious and slow, it's very difficult to treat with standard antibiotics and exacerbated by malnutrition and low immunity eg HIV infection.

Summary

Looking at the disease rules closely, I'd consider that disease as threat or potential stimulus for the player group probably deserves more of a show given the conditions of the Twilight World. I've not come across much mention of it in the Polish supplements I've looked through and if anything the conditions in Poland in the Twilight World of 2000 seem setup so that disease should be a common enough challenge encountered.

The detail and complexity of the rules in T2k v2.2 are considerable - 4 rolls to check if a character is infected and up to 5 rolls to check for recovery or death. On the one hand, this is probably one of the more comprehensive treatments in an RPG I've seen but on the other hand, it may be overly complex and present a barrier to its use during play.

Hopefully, the additional tables above help with this however and I think the whole "mini-game" can be summarised into set steps from the dense block of text (see the Appendix below).

Weighing up the probabilities and taking into consideration the resource-poor world, the role of disease in the game seems to be to help drive the player group towards larger towns and cities seeking advanced medical treatment or as a barrier to prevent them exploring in a particular direction.

You might have an APC, enough fuel, parts and food to make it to Bremerhaven and a good chance of dodging former Soviet soldiers if you keep off the roads but if one of you gets sick, say your mechanic, and you don't have the correct medicine that side trip into town may cost you precious time. Or do you make a decision to leave your plague-ridden companion behind...

Appendix: From Contact to Recovery (or Death) 

This is a summary of the "mini-game" of disease for easy reference by a Referee:

Contracting Disease

• On an Animal or Group (people) Encounter check for presence of disease (2D6 roll)
• Check if a character drinks potentially contaminated water (1 in 20 risk)
• Determine the type of disease according to the relevant table (page 274 or above)
• Check to see if the group detects the presence of a disease (Medical: Diagnosis or other)
• Referee to rule to determine if a character is potentially exposed 
• AVG:CON check to see if exposed character contracts the disease 
• Wait for the incubation period to pass and then inform player of symptoms

Overall, this involves four rolls: a 2D6 roll (check for presence), a D10 roll (type of disease) and two D20 rolls (detection check, CON check to avoid disease). Potentially could be simplified into four D20 rolls.

Treating the Disease

• In phase 1, check to see if the disease is diagnosed using Medical: Diagnosis

• IF the correct diagnosis is made, apply modifiers and check for recovery at the end of phase 1
• IF recovery roll is successful, then the character recovers and suffers the debility effects
• IF the roll is unsuccessful, check again at the end of phase 2
• IF the phase 2 recovery roll is successful, move to the debility phase
• IF the phase 2 recovery roll is unsuccessful, check for death
• IF the death check fails, the character dies
• IF the death check succeeds, apply debility 

• IF a misdiagnosis is made, apply any applicable modifiers and check for recovery
• IF recovery roll is successful (unlikely),  then the character recovers and suffers the debility effects
• IF recovery is unsuccessful, recheck diagnosis (half difficulty in phase 2)
• IF correct diagnosis is made, apply correct treatment and check recovery
• IF misdiagnosis still, check for recovery (less likely)
• Otherwise follow the same steps as above until death or debility 

This requires at least two D20 checks (diagnosis and phase 1 recovery rolls) but if the character is misdiagnosed in both phases increases to four D20 checks (two diagnosis checks, two recovery rolls) and a D10 roll (check for death). The D10 death check could be converted into a D20.