Leprosy is among the oldest human diseases, with descriptions of a similar illness in the Bible, afflicting people who spoke ill of others.
"Many of these biblical diseases have a stigma attached to them, because they can be very disfiguring," Hotez said.
He said mock funerals were often held for people with leprosy. "They thought it was a punishment for God," Hotez said.
Franco-Paredes treats roughly 300 cases each year, some of whom have not left the United States.
"It continues to be a problem, but it's also a disease of vulnerable populations from a socioeconomic perspective," he said. "Even nowadays, we don't know how leprosy is transmitted."
The disease attacks the skin and ultimately the body's nerve cells. It is caused by a bacterium similar to the one responsible for tuberculosis.
Franco-Paredes notes that recent efforts have simply prevented the disease from occurring more often, without preventing it from happening.
"The incidence of the disease has remained the same," he said.
The most common cause within the United States is exposure to armadillos, largely in eating them, he said, as well as having a farm of them or hunting them.
"The bacteria has been identified in armadillos, and the few cases we see that have never travelled, they have that risk factor of being in contact with armadillos," Franco-Paredes said.
He also noted that there is no evidence of human-to-human transmission, because people in the same household who have it tend to also share other risk factors.
"To acquire leprosy, compared with tuberculosis, you need a very long exposure," he said.
The problem in treating it that people tend to go for treatment when they reach later stages of the disease.
"We have good treatments and they're widely available, but the problem again is the late identification of these cases," Franco-Paredes said. "Until we understand better the epidemiology of leprosy and the transmission, I think leprosy will continue to be around.
"I'm sure we will continue to see cases over the next few centuries. With leprosy at this point, I don't think we can talk about elimination."
"In many respects, the rural American South at the beginning of the 20th century resembled a developing country, with high rates of hookworm infection. … Indeed, the pejorative concept of the "lazy Southerner" was partly a consequence of the toxic combination of chronic parasitism and nutritional deficiencies that plagued the region, as the [neglected tropical diseases] kept the southern population mired in poverty just as they do today in Africa, Asia, and elsewhere," Hotez wrote at the beginning of his chapter on tropical diseases in the United States in his book "Forgotten People, Forgotten Diseases."
The nutritional deficiencies and parasitic infections that plagued the U.S. South at the beginning of the 20th century have largely been dealt with, but the diseases still plague many living in rural poverty throughout the world.
The hookworm parasite, which lives in the soil, causes severe anemia in its victim and the infection can prove difficult to get rid of. Hotez has developed a vaccine for hookworm, but notes that further work will be needed.
While the infection may once have hurt the economy of the South, Hotez said, it now has the same effect in other parts of the world. Getting a hookworm infection has been correlated with lower income later on.