During the work on my West Africa setting I realized that I would need some
game mechanic for tropical diseases. During the time period of the setting the
region was known as the "white man's grave" because of the high death rate
of explorers and colonists, so the diseases should also be an element of the
The normal game mechanic of Call of Cthulhu / BRP includes daily CON rolls to
fight the disease and enables the characters to remain at least partially active
during the worst phase of the disease. I was looking for something less compli-
cated, but at the same time perhaps a little more realistic overall - in my view
a character who suffers from high fever and stomach cramps does not go hun-
Yesterday I posted some first thoughts on a possible game mechanic over on
BRP Central, this here is a more organized description which I post because I
would like to ask for your opinions, too.
First, there is a general probability to become infected with a disease, which is
modified according to the terrain (swamps are more dangerous) and the charac-
ter's precautions (like taking chinin and using a mosquito net).
Each of the major tropical diseases of the region (malaria, sleeping sickness, yel-
low fever ...) has a specific incubation period, a disease period during which the
character is incapacitated, and a lethality rate.
The character rolls for his basic probability to become infected, perhaps once per
month and more often in dangerous terrain, with a modifier based upon his precau-
tions. If he is infected, the specific disease is determined randomly.
If he had the bad luck to catch a disease, he rolls for the length of the incubation
period (different diseases have different incubation periods) and then also for the
length of the disease period (again, depending on the disease). During the disease
period the character is "out of business".
Finally the character rolls for his chance of survival, modified for his constitution
and the medical treatment he received during the disease period. Some diseases,
like the mild forms of malaria, are rarely lethal, other diseases, like the sleeping
sickness, always have a lethality rate of 100 % ...
I think (well, hope) that such an approach would still demonstrate the dangers of
the tropical diseases and would still simulate the differences between the diseases
(length of incubation period and disease period, lethality rate), it would still give
the character a chance for precautions and medical treatment, but with only four
die rolls it should not slow down the game too much.
Well, what do you think ?