Not long ago, Bill Gates had an idea: a personal computer in every home. Most people scoffed, thinking the idea to be ludicrous. His vision made him one of the worlds richest, most successful people, and it broke open the technological revolution upon us today.

Yet, with a few decades of personal computers having become commonplace, globally, we now understand that his real contribution was less the computer, but the social revolution that it enabled. Equally, the more profound impact of the $100 million Mr. Gates has now donated to find the cure for Alzheimers is the literal and profound reframing of global public health now and forever defined by the health needs of our aging global society. Malaria, HIV/AIDS, and TB have not been fully conquered, but with the most visible and energetic of the establishment philanthropists turning his sights to the disease of aging Alzheimers we have forever reimagined the contours of global public health.

As usual, Bill Gates gets it that the megatrend of population aging in many ways brought about by the 20th-century miracles of good and widespread hygiene, modern innovative medicines, and broad-based healthier lifestyles must now in our 21st century be joined by what Mr. Gates himself calls the next frontier where we can dramatically improve human life. Its a miracle that people are living so much longer, but longer life expectancies alone are not enough. That frontier will be to find the cures for the diseases of long lives, starting with the scourge of Alzheimers, which takes tens of millions of loved ones from us, costs trillions, and reframes social engagement, as the character of the disease is so devastating in its length and personal impact. Of all diseases, it is Alzheimers (and, technically, other dementias), which is nearly perfectly correlated with aging that has therefore turned it from a rare disease, when most of us died too young to get it, into an epidemic that is ravaging us all.

Enter Gates. Enter the most important Alzheimers donation from a public philanthropist. Enter a turning point in the fight against Alzheimers, for not only will the Gates money help lead to new, better research, but it will act as an enduring symbol of the global need as public health shapes its priorities in an era of aging populations.

In explaining why hes making this donation, Gates identified five areas where he believes we need to see progress: better understanding the disease; better diagnostics; a more diverse drug pipeline; faster clinical trials; and better use of data.

While each of these areas is absolutely valid and worthy of the Gates funding, it is worth asking: what else? As we reboot our public health agenda, other issues also emerge:

Caregiving inside the home. Its impossible to talk about Alzheimers without talking about caregiving. Unlike many other age-related chronic conditions, Alzheimers is a slow killer. People with the disease may live for decades as their cognitive functioning deteriorates, and an army of family, friends, and caregivers are called upon to provide support. The demands can be devastating. People lose their jobs. Caregiver health deteriorates. The costs pile up. So, as the global population ages, the demand will only intensify, and the gap must be filled. If Gates has brought us to a rallying point around Alzheimers, lets think of care as a new priority that equally defines our 21st-century public health agenda. If institutional care was the answer in the 20th century, in-home care is the answer for the 21st. And it is equally compelling to bring the innovations of the private sector, such as home care and remote care delivery, to inform and often lead public-sector policy.

NCDs, active aging, and functional ability. If Alzheimers is the most visible of the diseases of aging, this Gates-driven redefinition of global public health will now also lead us to reframe what the role of health policy might be in a time of long lives. As the new WHO Strategy on Ageing and Health lays out, there are the conditions of aging deteriorating skin, muscle and bone mass, vision, oral health, and hearing along with diseases like diabetes, cardiovascular, and cancer that, while they exist across our life course, have impact for most every one of us living past 60. This is new this idea that good health policy can enable functional ability for conditions of aging as well as diseases that afflict and this is what Gates is effectively achieving by moving his philanthropy from the targets of last century to the needs of this one. Wow!

In this era of tweet-storms and selfie-sticks, it can be easy to forget that the supercomputers that grace our pants pockets are the direct lineage of the once revolutionary idea of Bill Gates to have a PC in every home. So, too, that the cure for Alzheimers was joined by the vision of the man who brought us Windows, as he understood the plague will shortly affect more in Africa than Europe and more in Latin America than America as they, too, age at even more rapid paces. And with it we will have also changed the public health agenda to be led not by history, but by the realities of tomorrows population needs long lives and aging societies everywhere on the planet.