Priscilla Chan and Mark Zuckerberg on July 10, 2014 in Sun Valley, Idaho. 
Priscilla Chan and Mark Zuckerberg on July 10, 2014 in Sun Valley, Idaho.  - 

Why people donate is a mystery. And when it comes to giving money to help contain the spread of Ebola, charitable giving has been modest. This week, Priscilla Chan and her husband Mark Zuckerberg  the co-founder of Facebook   donated $25 million to help fight Ebola.

In an interview with Marketplace, Chan explains why one of the most prominent couples in the United States decided to donate millions to the cause  and what they hope they get for that money.

Thinking like a doctor

The gift  which Zuckerberg of course announced on Facebook  will go to the Centers for Disease Control and Prevention, with the idea that it will filter through to many different organizations on the ground.

Chan, who works as a doctor, explains her rationale this way: "As a pediatrician, [my] training is in preventing disease and keeping children healthy. And so we take advantage of  and are appreciative of  the massive vaccine program in our country to help prevent the spread of a more serious epidemic, of anything ranging from...flu to measles...and what I see as cases of devastating illness that would otherwise be preventable...I understand how important it is to act now to keep Ebola from being a massive problem that affects the lives of many, and the importance of prevention and early intervention."

What they're worried about

Ebola is, at present, a disease without a cure

"Right now we don't have an effective vaccine program...Not acting now might lead this to be a more pervasive illness that's harder to control later down the line,"Chan says. "The examples Mark brings up are diseases like HIV, Polio...infectious diseases that are so difficult for us to control, or in Polio's case, eradicate. But we have an opportunity now to act quickly and to really change the direction and growth of Ebola."

A larger donation than originally planned

Chan and Zuckerberg had been contemplating a donation for a couple of weeks, she said. Then, Zuckerberg took a trip to India. After seeing the lack of public health resources in the country's poor and rural communities first-hand, Zuckerberg called Chan and suggested they make a larger gift than they had previously been considering (Chan declined to say how much they increased the donation by).

How did she react?

"We definitely had to think about it as a couple, if this was something we really wanted to commit to...the need to respond has always been a no-brainer, the thing that changed with Mark's visit, and seeing the disparity in resources," she said. "[We decided] that we need to act now and make a larger gift, to be able to keep Ebola to a confined state, where we can aggressively intervene, rather than have it evolve into something that ends up having to be costly and linger in our worldwide community for decades."

Click the media player above for audio.

Follow Dan Gorenstein at @dmgorenstein