Each of them should donate $25 million to fund the eradication of Ebola. This would raise $2bn which should be enough to handle the outbreak (estimated to require $1bn) even with contingencies and to develop a vaccine.
Why is this important?
The least wealthy of the richest 85 is worth $11bn. $25million is less than 0.25% of their wealth and considerably less than that for the wealthiest. It'll make no difference to them but will save the lives of countless people.