The billionaire Paul G. Allen said on Thursday that he would donate $100 million to the fight against Ebola, which has killed almost 5,000 people so far and crippled Western Africa.

The amount roughly quadruples his earlier commitment of about $26 million to nonprofit groups and government agencies like the Centers for Disease Control and Prevention, making him one of the largest individual donors in the Ebola crisis.

“Everybody feels called sometimes to really pursue a certain thing that resonates with them, and this has resonated with me,” Mr. Allen, a co-founder of Microsoft, said in a telephone interview on Thursday.