MAUREEN CAVANAUGH (Host): The link between HIV infection and tuberculosis has become increasingly lethal. The World Health Organization says TB is now the number one killer of people who have HIV. A new report from the UC San Diego School of Medicine finds the burden of this co-infection is increasingly falling on the Latino community in Southern California. Here with us to explain this study and its medical implications is my guest, Dr. Timothy Rodwell. He’s a physician in the Division of Global Public Health at UC San Diego, and author of the new report on HIV and tuberculosis rates among Hispanics in Southern California. Dr. Rodwell, welcome to These Days.
DR. TIMOTHY RODWELL (Public Health Physician, UC San Diego): Thank you very much for having me, Maureen.
CAVANAUGH: And I’d like to invite our listeners to join the conversation. Call us with your questions and comments about tuberculosis or its treatment or this new study. Our number is 1-888-895-5727, that’s 1-888-895-KPBS. Dr. Rodwell, you’ve been studying infectious diseases and particularly tuberculosis for years. Why don’t we start at the very beginning. What is tuberculosis and how is it spread?
DR. RODWELL: Well, tuberculosis is a bacterial disease and it’s spread mostly by the airborne route, that’s coughing, sneezing, talking even.
CAVANAUGH: And what are the populations in Southern California who typically have tuberculosis? Do we have information on that?
DR. RODWELL: We do, actually. San Diego actually turns out to be an incredibly interesting population in terms of tuberculosis. It’s very unusual, it’s very much – it’s very different from the rest of the U.S. Over 70% of the people with tuberculosis in San Diego are actually born outside of this country.
CAVANAUGH: And do we have any idea where they’re contracting that tuberculosis?
DR. RODWELL: Mostly we look at, in cases like this, you know, the tuberculosis and epidemiology of tuberculosis in the U.S. is changing a lot. And mostly what we’re doing when we look at where they’re contracting is mostly the country of origin. So in San Diego, the country of origin, two of the largest groups in terms of country of origin problems with tuberculosis are Mexico and Philippines, for example.
CAVANAUGH: How is tuberculosis treated?
DR. RODWELL: Tuberculosis is completely treatable if you catch it early and it’s not a resistant bacteria—and we can get into that later—it’s actually completely treatable. It’s treated by not one drug but actually four drugs and over a long period of time. It takes at least six months. So you’re – if you have tuberculosis, active tuberculosis, and you need to be treated, you’re looking at minimum six months taking pills every single day.
CAVANAUGH: Every single day. Does that, the length of the treatment, interfere with the rates of recovery?
DR. RODWELL: It does. If you stop taking your tuberculosis treatment early, for example, there’s a good chance that you could actually create a resistant tuberculosis bacteria in your body. If you do that, you’ve bought yourself a lot longer treatment.
CAVANAUGH: Wow. Now, tell us about this connection between tuberculosis and HIV.
DR. RODWELL: So HIV is considered what’s called a potent risk factor for tuberculosis. If you have HIV and you come into contact with somebody with tuberculosis, they cough, sneeze, whatever on you, you are much more likely to actually get tuberculosis. Most people with a healthy immune system, haven’t got HIV, doing fine, if you cough tuberculosis at them just once, they’re probably not going to get it. They won’t actually get infected. Or even if they do get infected, they won’t go on to get active tuberculosis. If you have HIV and somebody gives tuberculosis to you, you’re much more likely to actually get active disease, the kind of disease that can kill you. You’re much more likely to die if you have HIV and tuberculosis.
CAVANAUGH: Now in the beginning, in trying to describe this, I said that HIV and TB together, this co-infection makes both diseases worse. Is that correct?
DR. RODWELL: That’s completely correct. Having HIV also makes your T – Having HIV makes your TB worse, and having TB makes your HIV worse. If you have HIV and you get TB, your HIV actually progresses faster. TB also makes your HIV treatment a lot more complicated. Taking drugs every single day for the rest of your life is what you’re going to be doing with HIV. You throw tuberculosis on that, for complicated drugs, you start having interactions, you start having problems.
CAVANAUGH: How – I’m just curious, therefore someone who had this co-infection, how many pills per day would somebody have to take?
DR. RODWELL: It all depends on what kind of drugs you’re taking. Different people aren’t treated exactly the same. Most people are treated the same but everybody is treated slightly differently for HIV, depending on what resistance profile they have. Everybody’s treated slightly differently for tuberculosis. Most are treated the same but it really depends on even the trade name of the drug you’re taking, so you could be taking a small handful of pills or you could be taking a large cupful of pills.
CAVANAUGH: Wow. I’m speaking with Dr. Timothy Rodwell. He’s a physician in the Division of Global Public Health at UC San Diego, author of a new report on HIV and tuberculosis rates among Hispanics in Southern California. And, Dr. Rodwell, how did you go about conducting this study?
DR. RODWELL: So this study’s done in close collaboration with San Diego County. The San Diego County like most of the areas – most of the regions in the U.S., collects tuberculosis data all the time and it goes into a national and a federal database. So what we did is, we looked at tuberculosis data from 1993 to 2007, so it was about 15 years worth of data, and we looked at the cases that are just regular tuberculosis and cases of tuberculosis with HIV. One of the reasons we actually started this study is because HIV-TB, like TB in the U.S., has mostly been going down in the rest of the U.S. but it’s stayed kind of stable in San Diego, stayed around 8%, well, closer to 9% of all tuberculosis cases in San Diego are HIV-tuberculosis cases. That’s higher than the rest of the county and so we were wondering why.
CAVANAUGH: And what did you find when you conducted this study?
DR. RODWELL: So what we found is that overall, there are ethic and racial disparities in HIV-TB, who has HIV-TB, and most importantly, over 15 years there’s been a change. And it’s not that there’s been getting – there’s been more cases of HIV-TB in the Hispanics, it’s just that they’ve been improving in non-Hispanic whites and non-Hispanic blacks but not in Hispanics. And so what that means is Hispanics now carry the greatest part of the burden of HIV-TB. It used to mostly be a disease of whites and blacks in San Diego. It is now over 80% Hispanics.
CAVANAUGH: And so the overall rate has not increased but the demographic has shifted.
DR. RODWELL: That’s correct.
CAVANAUGH: What – I wonder what – why that might be? What has your study found about why that might be?
DR. RODWELL: Unfortunately, that’s a question we couldn’t answer with the study.
CAVANAUGH: I see.
DR. RODWELL: The part of every – the first part of every problem is trying to understand the scale and scope of the problem. This is really step one for us, trying to understand that there’s really been a shift. So it’s not that things have been staying the same, it’s they’ve stayed the same in some groups while changed in other groups. Now we have to try and understand why. You can make – one could hazard a few guesses and one of the things that we’re thinking probably is most certain about this, if you look at the origin of most of the HIV-TB cases, over 60% of the cases from 1999 to 2007 were people that were born in Mexico. People that are born in Mexico have higher risks of tuberculosis than people born in the U.S. It’s as simple as that in terms of TB.
CAVANAUGH: And I saw a statistic in your report, I think, a summary of your report, a public relations release about it, and that you were – the infections – the typical person infected with this co-infection of TB and HIV would be a middle-aged Latino man who was also – used injection drugs.
DR. RODWELL: That’s correct.
CAVANAUGH: Is that correct?
DR. RODWELL: That’s correct, yeah.
CAVANAUGH: Now what role does the border play in this problem?
DR. RODWELL: So the border plays – this is definitely something that we assume is playing a large role in this region. We can’t prove it but it’s just something that we assume. And the San Diego region, as I said before, it’s a very unique and it’s a very unique region compared to the rest of the U.S. and it’s mostly because we have a population that flows back across the border. The border is not a barrier for disease and in this particular region, SANDAG, for many purposes, actually considers the Tijuana-San Diego region a giant metropolis. There’s – To give you some perspective, there’s 60 million border crossings per year between San Diego and Tijuana. And with only 3 million people in the county, that means that every man, woman and child crosses 20 times a year. Obviously not every man, woman and child does, so it means some people are crossing a lot more than that. And what that means is that you’ve got a population that’s fluid between both sides and that the risk factors for this particular disease, tuberculosis in particular, is different on either side of the border. So you’ve got a population flowing back and forth with different disease risks on either side.
CAVANAUGH: I’m speaking with Dr. Timothy Rodwell. We are taking your calls if you have questions, 1-888-895-5727. We’re talking about a new report on HIV and tuberculosis rates conducted by UC San Diego School of Medicine here in Southern California. And I’m interested in what you said before, Doctor, about the fact that this seems to be a hot spot in the nation when it comes to tuberculosis.
DR. RODWELL: It most certainly is. Right now, the incidence of tuberculosis in San Diego is about double that of the nation, so it’s about, you know, if you look at it in terms of actual numbers, it’s not high compared to the rest of the U.S. and it’s important to keep that in perspective. We have about 9 cases per every 100,000 people in San Diego, whereas the rest of the U.S. is about four and a half cases per 100,000, and that’s many times lower than in Africa, for example…
CAVANAUGH: Certainly, yeah.
DR. RODWELL: …or even across the border in Baja, California.
CAVANAUGH: And yet you say that the idea – the tuberculosis in and of itself is not that highly contagious if you are a healthy person.
DR. RODWELL: That’s correct. Most tuberculosis being transmitted from one person to another won’t be like influenza. It’s not going to happen just from one interaction in an airplane or in a room. It’s the kind of thing that usually happens with a lot of interaction. To give some perspective of that, even once you’ve actually gotten TB, most people with a healthy immune system actually only have a one in ten chance of ever actually getting the disease of TB. So you have an infection of TB and most people can have an infection of TB that just sits quietly in their lungs and never does anything for the rest of their lives. In fact, nine out of ten, it never does anything.
CAVANAUGH: Is it one of these diseases and it not only affects people who have compromised immune systems but also the very young and the very old?
DR. RODWELL: That’s correct in terms of – in terms of mortality, the very young and the very old are much worse affected by TB, the active disease. In terms of the disease going from latent to active, it can be worse when you’re older.
CAVANAUGH: Now I don’t know if you can answer this but I know a lot of people listening to us talk and hearing about the relatively high rate of TB infection we have here in San Diego, even before the demographics shifted, will ask why. Can you speculate for us?
DR. RODWELL: We can only speculate mostly – we can only speculate on our relationship with our neighbors and our relationship with all countries that have higher rates of tuberculosis than the U.S. So if we look at our tuberculosis numbers, 70% of the cases in San Diego County are people that were born elsewhere, people that most likely came in with latent tuberculosis, the sleeping form of tuberculosis. And so I would say one of the largest things, if we had to point at anything, that would be the largest thing, is that we have a large immigrant population here and that population is at a higher risk when they came in in the first place. It’s also important to understand that most of these immigrants that we’re talking about in this particular study, HIV-TB, these are not recent immigrants. The average age – the average number of years that an immigrant with HIV-TB has been in the U.S. is 13 years. These are people that are a part of our community. This is our community.
CAVANAUGH: Right, this is not a contagious disease that’s being brought from one country to another, it’s here.
DR. RODWELL: That’s correct.
CAVANAUGH: I wonder if you’d talk to us a little bit about the various strains of TB because I understand that we are also unique in the kind of tuberculosis that we have in San Diego.
DR. RODWELL: That’s correct. This is, again, something very unusual for San Diego. There’s a number of species of tuberculosis that can cause disease in humans. One of these species is called Mycobacterium bovis, which is actually – mostly used to be a disease of cows. Back before milk was pasteurized, it was a disease of humans throughout the world. It was about – anywhere between 15 to 30% of all TB was actually caused from this. Now, in the developing world, Mycobacterium tuberculosis – uh, Mycobacterium bovis hardly causes any disease in the developing world except in San Diego. Almost half of the cases of children with tuberculosis in San Diego actually have this bovis form of the disease and it’s most likely contracted from unpasteurized milk products.
CAVANAUGH: Is it more difficult to treat?
DR. RODWELL: It’s more difficult to treat only in one sense, is that it – Mycobacterium bovis has a natural resistance to one of the drugs that we use to treat tuberculosis, so off the bat, if somebody comes in with bovis, they – You know that you can’t treat them with just the usual drugs, you have to actually treat them with different drugs. What that means as well is that they have to be treated for longer. They have to be treated for 9 months instead of 6 months.
CAVANAUGH: Now I know that you’re a researcher and you don’t have anything to do with how San Diego County Public Health actually tracks people with tuberculosis here, but are you familiar with what is commonly done since this is a contagious disease? Do public health officials in various places track people with tuberculosis?
DR. RODWELL: Absolutely. Absolutely. In San Diego County, we have a very active tuberculosis program, as you can imagine, since numbers are quite high here compared to other areas. And every case of tuberculosis is tracked. Every case of tuberculosis, the treatment is followed.
CAVANAUGH: I’m wondering, for people – because I’m trying to imagine people listening to our conversation here. If someone they know is sick, it doesn’t sound as if that there is a really high probability that they would contract this disease if they’re not sick themselves.
DR. RODWELL: That’s true and it’s not true.
CAVANAUGH: Okay.
DR. RODWELL: It’s not true in the sense if you’re just happen to be on one bus ride with somebody in the bus with tuberculosis. But if somebody in your household has tuberculosis, that’s not true. You’re going to be exposed to it over and over again until you’re going to get it. Now getting infected, as I said before, doesn’t mean you’re necessarily going to go on to active disease but you still have a one in ten chance that you will. That’s also a slight oversimplification. In the first couple of years that you first get infected, you have a – most of that risk actually comes in those first couple of years.
CAVANAUGH: Ah, I see. I see.
DR. RODWELL: So this is sort of a lifetime thing versus a short term thing. It’s a very complicated disease.
CAVANAUGH: And in the risk group that your report identifies, intravenous drug using, middle-aged Latino men, that sounds to me that it might be a hard demographic to try to get on this program of daily drug intake.
DR. RODWELL: Extremely difficult. And I think that’s one of the complications. San Diego’s HIV population and injection drug using population is not very well understood actually, and there’s a couple of people, one of the other authors, Dr. Richard Garfein, on this paper, is actually a person leading up a study trying to understand that exact thing, trying to understand injection drug users in San Diego, trying to look at how we can reach out to them for prevention of HIV, the prevention of TB, and treatment of those as well. But you’re absolutely right, they’re a difficult group to treat. Many of them are homeless, so it’s one of those things that if you have to give them pills every single day, it becomes complicated. One of the ways they do this with tuberculosis treatment, because it’s not like HIV, it’s not a lifetime, is they actually can provide housing, so in some cases when it’s bad enough, they’ll actually provide housing for the duration of the treatment of tuberculosis.
CAVANAUGH: I’m wondering, Dr. Rodwell, what recommendations do you make in this report?
DR. RODWELL: So the strongest recommendations we have in this report, is, again, it’s leading – tuberculosis in this county leads us to look at our relationship across the border and our relationships across the border are strong and growing stronger. And one of the strongest recommendations we have, therefore, is to make sure that everything that we do about tuberculosis should be a binational effort to make sure that we use resources in an intelligent, binational manner, that we’re fully engaged and working with our partners across the border. And so one of our strongest recommendations is to make sure that we continue to strengthen those relationships.
CAVANAUGH: We’re out of time but I want to thank you so much for coming in and speaking with us today.
DR. RODWELL: Thank you very much for having me.
CAVANAUGH: I’ve been speaking with Dr. Timothy Rodwell. If you’d like to comment on what you’ve heard, please go online, KPBS.org/thesedays. And coming up, we’ll explore the mystery of a baby’s brain. That’s next as These Days continues here on KPBS.
