The world's most difficult problems don't exist in isolation, and neither should the work to solve them, Melinda Gates told a national philanthropy conference in Seattle on Monday.
Philanthropists need to work together with business and government to be more effective, said Gates, co-chair of the Bill & Melinda Gates Foundation.
Even the Gates Foundation, with its $33 billion endowment and global influence, doesn't have all the answers.
"We're a young organization," she said. "We're learning, we're trying things and we're changing. The list of lessons we learned is just about as long as the list of mistakes we've made."
The foundation started with the principle that all lives on the planet are of equal value.
"Children who are starving in Africa or India or Bangladesh are just as important and precious as my children are or your children are," said Gates, who got her first taste of philanthropy in high school by volunteering at a hospital in her native Dallas.
She and her husband, Microsoft co-founder Bill Gates, found a role for themselves harnessing scientific advances to help solve neglected diseases in the developing world.
"We're living in an age of unprecedented innovation. You can get your e-mail and your text messages in the palm of your hand as you sit here," she said. "We mapped the human genome. Right now we have the ability to solve the biggest problems like never before."
While the foundation has made strides in global health, there are still "literally billions of people suffering in the world today as we gather for this breakfast," she said.
The room fell silent when she remarked that all 2,000 seats in the audience could represent the number of children dying from malaria every day.
Some lessons have been basic. Last month the Gateses traveled to Vietnam, a country with a 90 percent vaccination rate for children, she said.
When the country was ready to introduce a new vaccine for rotavirus, which causes severe diarrhea in children, it hit against a simple obstacle.
The vaccine comes in a very bulky package, but the refrigerators used for storage are tiny and full most of the time.
"All that research and development and guess what, the problem is the size of the box," she said.
Other lessons are more complex. The foundation has been studying how it might get involved in clean-water projects. Shortages of food and clean water can't be separated from other health problems, she said.
During a trip to India, Gates said, she saw poor children in slums waiting in a long line to fill old turpentine bottles from a tiny spigot that worked only in the morning. She talked with women in rural communities who were spending three to five hours a day searching for clean water in the mountains.
Solutions are not easy to find, and after two years of study it's not clear the foundation has enough expertise in water to make it a core focus, she said.
"By ourselves we can't make a dent in any of the problems we've chosen to focus on," she said.
Even assets of $30 billion are a drop in the bucket, she added. The entire endowment couldn't cover the cost of educating California students for one year — about $60 billion.
Gates ended her speech by talking about a little girl she met in Mozambique a few years ago who was feverish and dying of malaria. After the right treatment, she recovered and is now living a healthy life.
In her lifetime, Gates said, she can imagine a world in which the girl's story is "is not a miracle anymore but a routine fact of life."