Anew study says targeting treatment programs at specific neighborhoods may be a better way of controlling tuberculosis in some cities. The study looks at so-called TB hotspots.

Lead author Dr. David Dowdy said a hotspot is a “geographically defined area” where TB cases are most prevalent. Dowdy is an assistant professor of epidemiology at Johns Hopkins School of Public Health.

Rio hot spots

“We looked at the city of Rio de Janeiro that has a population of about 6 million individuals and identified three geographic areas that have populations between about 50,000 and 250,000 where TB incidence was higher. So a hotspot is a geographically defined, smaller area of a larger city, in this case, where TB seems to be transmitted at a much higher rate,” he said.

But if most of the people in Rio de Janeiro live outside of these hotspots why should they worry about TB infections?

Dowdy said, “Tuberculosis is a disease that’s transmitted in airborne fashion. So any individual is susceptible to TB and can pick it up from anyone else. This can be on the bus. This can be in a shopping center. This can be out on the street. And what we found was that much of the TB transmission to people outside of these hotspots actually originated from these hotspots, such that if tuberculosis were better controlled within the hotspots TB rates in the entire city would go down.”

It’s long been known that these TB hotspots exist.

“TB has since the 1800s been a disease of poverty, such that individuals with fewer resources, poor, more crowded conditions, etcetera, have always suffered the brunt of the burden of tuberculosis,” he said.

It’s already being done for other diseases, but the concept was never widely accepted for tuberculosis.

“Sexually transmitted diseases, malaria, other parasitic diseases. This has been widely known for a long time that targeting the areas of highest transmission can have dramatic impact on community-wide rates of disease,” he said.

The study applied that concept to Rio’s TB hotspots.

He said, “We found that if you were able to take these hotspots and bring them not to zero but to the same TB rates as the average of the rest of the city that you could have a reduction in TB across the city that would be similar to reducing TB rates in the rest of the city by 50 percent.”

Dowdy added that Brazil is taking the idea a bit further as it gets ready to host some major international events.

“I think also something that Brazil is doing actively right now in preparation for the World Cup and the Olympics is simply trying to improve the economic conditions as a whole in these areas. If people aren’t as crowded, if they have more access to healthcare, if they have better living conditions – all of those things are known to improve TB rates as well,” he said.

Another factor taken into account is the HIV/AIDS rates. TB and HIV are very closely linked because people with weakened immune systems are more susceptible to tuberculosis.

Vaccination

The Johns Hopkins professor said targeting TB hotspots is similar to vaccinating a city.

“We like to think of it that way. We think of treatment of TB as an investment in the future because if TB rates can be brought down today that means less TB transmission in the future. The difference between TB treatment and a vaccine is that treatment directly benefits the person receiving the treatment at that time. So not only do you benefit the person who has the disease, but you also make an investment for future generations as well,” he said.

Dowdy said, however, the Rio model may not apply to African cities. He said while the TB hotspots are well integrated within the Brazilian city, in Africa, many of the areas of high TB transmission are on the outskirts of cities. He says new models could be developed to determine whether targeting the outlying hotspots would have a major effect on overall TB rates.