Mass incarceration in Central and South America in recent decades has driven an escalating tuberculosis crisis within prisons, threatening progress against one of the world's deadliest diseases, according to new research. 

Despite making up less than 1% of the population of Central and South America, incarcerated people were responsible for 11% of tuberculosis cases in the region as of 2018, an international group of researchers from institutions including Stanford University and Yale University found in an April 8 paper in The Lancet. 

"The fact that we see epidemics occurring among the most vulnerable populations should be a wake-up call for urgent action,"  lead author Katharine Walter, a postdoctoral infectious diseases research fellow at Stanford, told The Academic Times. "These epidemics should not exist." 

Since 2000, the Central and South American prison populations have soared by more than 200%, leading to overcrowding in prisons and jails, many of which lack adequate sanitation and medical resources, Walter and her co-authors found. Over the same period of time, reported tuberculosis cases in prisons skyrocketed by 269%. 

Tuberculosis, an infectious disease that primarily affects the lungs, killed 1.4 million people worldwide in 2019, including 200,000 with HIV. While the disease is rare in most wealthy countries, the number of annual tuberculosis cases has stagnated or risen across Central and South American countries in recent years, driven in large part by prisons, according to the researchers. 

Walter said that prior to the COVID-19 pandemic, tuberculosis globally killed more people every year than any other infectious disease, including HIV/AIDS.

The role of prisons and jails as breeding grounds for disease has received more public scrutiny during the coronavirus pandemic. In the U.S., 34 out of every 100 incarcerated people had contracted COVID-19 as of mid-April, compared with nine out of every 100 Americans in general, according to a New York Times tally. 

And since tuberculosis and the coronavirus spread in similar ways, reducing overcrowding is key to reducing the spread of both diseases, Walter said. 

"Because airborne transmission occurs for both these pathogens, in places like prisons and other places where people congregate and there's poor ventilation, there's lots of potential to facilitate the spread of these pathogens," she said. "Not only is transmission risk elevated within these detention centers, but also by the movement of people between detention centers."

From 2011 to 2017, the number of yearly reported tuberculosis cases in Central America quadrupled from about 538 to 2,489. In South America, cases more than doubled from 7,798 to 17,285, the researchers found. The countries that recorded the biggest surges were El Salvador and Venezuela; in El Salvador, prisons are so crowded that they're operating at 348% of capacity, according to the researchers, who obtained incarceration data from the online database World Prison Brief. 

Other researchers have examined the spread of tuberculosis among incarcerated people, such as a 2011 paper led by Simon Johnstone-Robertson of RMIT University, which found that overcrowding contributed to an annual tuberculosis infection risk of 90% for inmates in a South African prison. But less attention has been paid to how tuberculosis in prisons affects nationwide trends, a gap in the research that Walter and her colleagues sought to fill. 

Walter is working on a follow-up paper that examines the spillover effects of prison tuberculosis cases on surrounding communities. 

Another Lancet paper published in February found that in the U.S., increases in the incarceration rate were associated with significant upticks in death in surrounding communities. The addition of one prisoner per 1,000 residents of a given county was associated with a 6.5% increase in deaths from infectious disease, a 4.9% increase in deaths due to respiratory disease, a 2.6% increase in substance abuse-related deaths and a 2.5% increase in suicides within that county after one year, when examining individuals under 75 years old. 

Walter and her co-authors said that while efforts to give incarcerated people more space and better medical care are worthwhile, slowing the spread of diseases in prisons and jails will ultimately require drastically reducing the number of people behind bars. 

"To minimize the population put at increased risk of tuberculosis, governments will need to reduce incarcerated populations and find alternatives to criminal justice policies that rely on detention," the researchers wrote. "Incarceration should be considered a last resort and alternatives such as restorative justice approaches should be made available in its place." 

The paper, "The escalating tuberculosis crisis in Central and South American prisons," published April 8 in The Lancet, was authored by Katharine Walter, Leonardo Martinez and Jason R. Andrews, Stanford University; Denise Arakaki-Sanchez, Brazil Ministry of Health; Victor G. Sequera and Alberto L. García-Basteiro, University of Barcelona; G. Estigarribia Sanabria, Caaguazú National University, Paraguay; Ted Cohen, Albert I. Ko and Julio Croda, Yale University; Zulma Vanessa Rueda, Universidad Pontificia Bolivariana and University of Manitoba; and Rafael A López-Olarte and Marcos A Espinal, Pan American Health Organization.