The contagion began with a bank manager in Cincinnati. Before long, it had spread to Austin, Pensacola, St. Louis, San Antonio and beyond.

Beth Dahle was exposed while visiting in-laws in Ohio last year. Within weeks of returning home to Wynnewood, she passed it along to a close friend, Mary Broach, and then to 109 other area women. Eventually, 25 families will be relocated as a result.

Don't bother checking with the Centers for Disease Control and Prevention for more information. The "epidemic" is philanthropic, not pathologic.

Dahle and hundreds of other women, here and across the country, have been swept up in a remarkable grassroots charity that has been growing exponentially since it first took hold eight years ago.

It is called Impact100 and is elegant in its simplicity: 100 or more women in a community pool $1,000 each to create grants of $100,000 or more. They seek applicants for the grants, review proposals and ultimately vote to determine who receives the money.

In Cincinnati, where Impact100 got its start, more than $1.4 million has been awarded since 2001. In Austin, the local chapter has grown to more than 500 women, meaning it can give five $100,000 grants a year. In all, there are nine chapters nationwide, with four more in the works.

Impact100 Philadelphia, with 111 members, has just awarded its inaugural grant, $111,000, to the Philadelphia Committee to End Homelessness (PCEH) for its SafeHome Philadelphia project. The money will be used to find long-term housing for 25 families that otherwise might be bouncing from shelter to shelter.

The grant is the largest PCEH has ever received.

"A grant like this is very powerful," Steven Shapiro, president of PCEH, said. "It can alter a small nonprofit like ours and enable us to accomplish something significant."

Which is one of the aims of Impact100 Philadelphia.

"We want to help relatively small, lesser-known nonprofits," said Dahle, co-president of the local chapter. "These would be generally groups without access to this kind of funding. We want it to be for new programs or an expansion of a program."

Dahle, 44, gets credit for bringing the Impact100 concept to the region. She heard about it during a visit to Cincinnati, where Impact100 has played a large philanthropic role since it was first conceived by Wendy Steele, then a senior vice president of the Huntington National Bank.

Steele wanted to make it easier for women with little time for volunteering - stay-at-home mothers and those with demanding careers - to get involved in philanthropy that made a difference.

"I wanted to give them the opportunity to write a check and be part of a significant gift to the community," she said. "It is a very simple idea, very easy for people to understand, and, yet, very powerful, and life-changing."

The concept also allows for women with the time to get as deeply immersed as they want.

Karen Nathan, of Wynnewood, for instance, has plunged in since joining Impact100 Philadelphia.

"If you want, you can just write a check," she said. "For me, it was a way to really be involved in the whole process. The idea of learning how to read a grant proposal, being about to make site visits and see how the organizations work on the ground was great."

And then too there is the unexpected fellowship created when scores of committed women meet in a common effort.

"It has been wonderful how much I've enjoyed meeting the other women," said Broach, cofounder with Dahle, of the Impact100 Philadelphia. "We have such a diverse group. We have women in their 20s, many stay-at-home mothers, working women in their 40s and 50s. We have a couple in their 80s."

Now Broach and Dahle hope to spread the fever further.

"If every one of our members finds one friend to join, we would be at 200," Dahle said. "We would just love to be able to give two $100,000 grants next year. Or more."

More Information

On the Web: www.impact100philly.org

E-mail: info@Impact100Philly.org

Phone: 610-668-2289

Contact Christopher K. Hepp at 215-854-2208 or chepp@phillynews.com.