Two years ago, a massive earthquake devastated Haiti. My first visit to Haiti was in May 2010, four months later.

I went with a photographer and the director of my medical relief and development organization, Global Links, to explore ways that we could help rebuild a public health system that had been grossly inadequate even before the earthquake hit.

The heat was stifling, and everywhere were crumbling mountains of rubble and collapsed buildings, sprawling tent cities and the drone of U.N. security trucks. These surreal images, which seemed more like those from a war zone than a tropical Caribbean nation, were still fresh in my mind as I traveled again to Haiti last July.

A particular memory from 2010 was that of a little brother and sister climbing up a hill out of a tent city in Delmas wearing crisply pressed clothes and bright smiles as they trekked to school. Were they and so many other displaced victims still living in tent cities or had the housing situation improved?

And what about the Haitian doctors we had met in 2010? Were they still able to work, given the constant shortages of supplies and their intermittent paychecks?

Alone on this visit, I exited the plane and was grateful for the 82-degree breeze that greeted me. The mounds of debris and rubble along the main thoroughfares had been cleared, and the roads were in much better shape. The hotel where I stayed was beautiful, with no remaining signs of earthquake damage, but next door was a building in total ruin, a perfect juxtaposition.

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In the days that followed, I visited hospitals in Aquin, Port Salut, Grand Goave, L'Archaie and Mirebalais. It was encouraging to talk with their staff members.

Global Links' medical supplies had been used during the peak months of the cholera epidemic, and the beds we shipped had helped the hospitals revamp their patient wards. Our donations were achieving their goals, and the hospital workers were grateful, even though they always need more equipment, medications and other supplies and often go without pay for months. Almost every hospital I visited was short of infant incubators and warming stations, birthing tables and much, much more.

Haiti's two primary health issues -- sanitation and access to clean water -- remain ever-present. This is due mainly to a lack of investment in basic infrastructure and housing.

In a country with no formal equivalent to "low-income housing," whatever emergency shelter is provided by the international aid community becomes long-term housing. Tents spread and turn into tent cities; temporary shelters become shantytowns.

Therefore it is no surprise that cholera hotspots are now mostly in the settlements where the emergency trucking of clean water is petering out. It is no surprise that violence has become a major health problem and is now the subject of a major public information campaign in the capital of Port-Au-Prince.

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Tragically, some 634,000 people still live in displacement camps, and real rebuilding has barely begun. All over the greater Port-Au-Prince area, I saw tents and makeshift shelters that offer little relief from 100-degree temperatures and are highly vulnerable to flooding, landslides, hurricanes and other natural disasters.

I lived through Hurricane Hugo in Puerto Rico. Even cement block buildings were destroyed. Living out the hurricane season in Haiti in a tent or temporary shelter is unthinkable.

But I also have seen signs of hope. The intelligence and resiliency of the Haitian people are reflected in the commitment of the doctors working to improve their homeland.

Dr. Douly Caillot, for example, was one of the first Haitian doctors to arrive with the Cuban Medical Brigade after the 2010 earthquake, leaving his medical school studies in Havana to be of service to his native country.

I met Dr. Caillot in June 2010, and since then he has set up his medical practice and purchased an ambulance to provide free emergency services and health care.

Another Haitian native and a graduate of the Latin American Medical School in Havana, Dr. Patrick Delky, re-opened an elementary school in his hometown of Madiste, St. Michel de l'Attalaye. The school serves 145 children in a very poor community. They often attend school malnourished and with health problems. So he also opened a clinic to meet the basic health needs of the schoolchildren and their families.

"These kids lack everything, even birth certificates," Dr. Delky told me.

It is amazing to see these Haitian doctors giving their time and money from their own pockets to improve Haiti's public health system. As Dr. Delky put it, "We are of the generation that believes that things can be different and change is possible. Therefore we are dedicated in heart and soul to this mission."

People like Dr. Caillot and Dr. Delky, and those who support them, are ultimately what will lift up Haiti.