On September 11, 2001, even as the disintegration of flaming towers forced terrified New Yorkers to flee the disaster site, thousands of medical volunteers began streaming in from the other direction. Driven by impulse and raw instinct, some already adorned in scrubs and stethoscopes, the volunteers converged on Ground Zero. But, for the most part, their inspiration was met with irony. Not only were tower survivors few in number, but the unfamiliarity of the volunteers to local emergency leaders compounded confusion for all. While some of these heroic volunteers ultimately tended to the injured, most were turned away. Eventually, as the drama receded and the volunteers also retreated home, their altruism went largely unnoticed and unrecorded. Sadly, good will did not translate into public good.

That frustrated generosity, however, has since served to catalyze a new chapter for public health. As a former Massachusetts state commissioner of public health who served during the national challenges of 9/11 and the anthrax scare, I believe our future depends on talents drawn from every untapped resource. Our country has long enjoyed the proud national volunteer traditions embodied by the Peace Corps, AmeriCorps and similarly directed initiatives. Public health in the 21st century can also tap this rich reservoir of good will, as seen on September 11.

Indeed, it was in this spirit that the Medical Reserve Corps (MRC), a national network of local health volunteers, was born in 2002. Coordinated nationally by the Office of the Surgeon General, MRC units represent vital community-based volunteers who heed the call to service and are identified, screened, trained and prepared in advance. Their sponsoring organizations, which can include local health departments, emergency management agencies, and other organizations, champion recruitment in local communities.

Each local unit balances the necessary mix of volunteers. Nurses now comprise almost one-third of MRC volunteers nationwide; furthermore, more than 13,000 doctors with specialties ranging from surgery to psychiatry have signed up. Other committed medical and public health volunteers include pharmacists, veterinarians, dentists, and mental health professionals, while non-medical volunteers can assist with logistics, administration, planning, and communication. Of particular note, students are playing an increasingly vital role; over a dozen units are based primarily in colleges and universities and more than a hundred have student volunteer members.

To date, MRC ranks have swelled to more than 160,000 volunteers at over 775 sites nationwide. All have registered in a local unit, support ongoing public health initiatives, and stand ready to serve in the event of a public health emergency.

Many locales have already witnessed the new power of MRC volunteers. In the aftermath of Hurricane Katrina in 2005, MRC volunteers nurtured thousands of weary evacuees seeking refuge many miles from home in Texas, Mississippi, Massachusetts and other states. During the 2007 Southern California wildfires, MRC personnel cared for the exhausted at more than 15 shelters across the affected region. Recent Hurricanes Gustav and Ike mobilized MRC volunteers to support shelter operations and provide first aid in nearly a dozen states in the South. Nationwide, MRC volunteers have not only conducted pandemic influenza trainings but also now routinely staff annual flu vaccination clinics that would otherwise lack qualified health personnel. And, in the worst-case scenario of a bioterrorist threat, MRC members are committed to dispensing antibiotics and prophylaxis to thousands of their neighbors.

Through their service, local MRC volunteers provide stewardship for an evolving post-9/11 public health system that increasingly values fierce interdependence. Integrating medical officials, public safety authorities, business, media, academia, community groups and others is not easy. For the MRC, systems for pre-identifying, registering, credentialing, and training volunteers need further development. And despite 2007 federal legislation that codifies the MRC, funding and sustainability challenges remain. But by offering both helping hands and a trusted presence to fellow residents, volunteers can bolster community resilience in this uncertain era of emerging health threats.

Last month, our country recognized yet another anniversary of September 11. In reviewing the shifting kaleidoscope of national events since that fateful day, we should honor the spirit of service that unites us at a time when too many neighbors remain strangers to one another. Connections in the midst of crises can make our communities stronger. As we review the past and look forward to the future, let us reaffirm one example of hope for health that arose out of the ashes.

Dr. Howard Koh is Associate Dean for Public Health Practice and Harvey V. Fineberg Professor of the Practice of Public Health at Harvard School of Public Health. He is the former Massachusetts Commissioner of Public Health.