On page 3, it says 1d4 townsfolk die each day for the first two days and then increases by 1d4 for every day thereafter.
On page 5, it says the journey takes a little more than three days (for a party moving at speed 30) or five days (speed 20) one way. Not counting time for exploring or resting.
Page 3 also states, once forty townsfolk die the malady has run its course.
Doesn't this make it near impossible for the party to complete the mission in time to save anyone ? The average death toll for six days would be 40 and I imagine most parties would have someone at speed 20. Even at speed 30 most parties would be likely to fail.