"We made the miserable decision to stop everything at that point," Silveira said, after her son had been taken off the transplant list for the third time and his pediatrician said there was nothing they could do to stop the virus. "All he needs is a heart. As a parent, you just don't understand it at the time."
But procuring a healthy heart can be difficult compared to other organs. While the organ transplant waiting list is national, people waiting for hearts are limited to donors from their own region because a heart needs to be in a recipient's body no more than six hours after it is taken from a donor's body. By contrast, livers and kidneys can travel farther because they can last up to 18 and 24 hours outside the body, respectively.
And the criteria for donating organs are stringent. According to Pam Silvestri, spokeswoman for the Southwest Transplant Alliance in Dallas, only people who die in a hospital and on a ventilator are eligible to donate their organs. Of those roughly 20,000 people, about 5,000 are ruled out because of organ damage or diseases such as HIV. But not all eligible people choose to donate.
"Culture may also be very important," said Dr. Ileana L. Peña, an American Heart Association spokeswoman and a cardiology professor at Case Western Reserve University in Cleveland. "I'm Hispanic, and Hispanics may have a very different view of cardiac transplant and devices than their Caucasian counterparts."
Cunningham echoed this idea.
"It's kind of taboo, even in the African-American community," she said.
Cunningham, who has been raising awareness about organ donation since her daughter's death, said she found much misinformation about the subject within her community. People think they cannot donate because they are sick or diabetic or have high blood pressure. Many people believe registering to donate organs puts them on a targeted list in a vague conspiracy theory.
"It's just a no-win situation on both ends," she said.
Cunningham is in the process of creating a comprehensive site with resources and information on organ transplants, in hopes that it will help people to consider registering to be donors.
Although medical director Johnson said none of this would be an issue if enough people donated organs, she said the research might be a good starting point to look for holes in the transplant system and overall trends.
"The next step will be to look at what are the things that predict mortality overall and if there is a difference in distribution among ethnic groups. ... We can then work on things to make access to organs more equal," Johnson said. "Certainly, our goal is to never have a death on the waiting list."
ABC's Dan Childs contributed to this report.