Dallas, TX – naa
Students in Denton and Ellis counties have recently tested positive for tuberculosis. But TB isn't unusual for North Texas. Dallas County, for instance, had 188 cases of the disease last year. In a KERA Health Checkup, Sam Baker talked with Dr. Garry Woo. He's the Medical Director in charge of Tuberculosis Control for Dallas County Health Services.
Dr. Garry Woo: Tuberculosis is a respiratory infection that's transmitted from individual to individual through the air. It's transmitted by coughing, singing, laughing. And this is due to the fact that the bacteria that lies in the hosts' cases aerosolized in the air, and other people in the room are susceptible to this infection by breathing the air.
Sam: How does one contract or develop the disease?
Dr. Woo: It has to do with the length of your exposure to the individual, it has to do with your immune system, and it also has to do with the virulence of the organism. Actually, there's two forms of the disease: The latent or positive skin test form, and that's characterized by positive skin tests, normal x-ray, no symptoms. And only ten percent of those people, in their lifetime, will progress to the active disease, which is characterized by cough, fever, weight loss. The second scenario, those are the individuals who are infectious to other people.
Sam: Is it curable?
Dr. Woo: Oh, the disease is easily preventable and curable. Individuals who have been exposed to the disease, who have a positive skin test, again normal chest x-ray, no symptoms, they can prevent progressing by taking nine months of isoniazid.
Sam: A pill, we're taking about?
Dr. Woo: Just one pill a day for nine months. We can provide it at no cost.
Sam: Who's most at risk?
Dr. Woo: Children younger than five because of their immature immune system. Certainly older individuals who may be suffering from other medical illnesses. And, of course, the H.I.V. population. Those people are susceptible to all infections.
Sam: A reasonably healthy person has less to worry about, I would assume?
Dr. Woo: Less to worry about, especially if they've had casual contact with the source case. For example just passing by, participating in an athletic event with this individual, saying hello - the risk would be very minimal. When we talk about prolonged contact, we're talking about perhaps 40 to 80 hours over a two to three week period, someone that you would work closely with. Certainly we'd concentrate on individuals who actually live or work with the source case.
Sam: Does anyone know, at this point, what is behind - for lack of a better word - this resurgence now?
Dr. Woo: I would say this: What occurred in Ellis County, and of course, Ellis County is taking the lead in their geographic region, they had a higher number of cases. In 2010, they only had three cases. And by count, they have somewhere between eight and ten now. And, of course, they many not have the same resources Dallas County does.
Sam: So, in the meantime, what can local officials do to fight against TB?
Dr. Woo: What occurs, and it's occurring in Ellis County, is you conduct a contact investigation around the source case. You look for secondary cases and individuals who have evidence of exposure to the disease. You would give them isoniazid to prevent and stop the spread of the illness. However, it takes time to come up with a list and it's a fairly arduous process in that you would have to interview every individual. So, you have one source case, maybe eight to ten secondary cases, and you know, they're interviewing household contacts, family contacts, work contacts, and, you know, who these people recreate with. That's a lot of leg work, a lot of skin testing and, basically, plain Jane public health work.
Sam: Sure, you really have to identify a case or suspect a case before the rest can go into effect?
Dr. Woo: Precisely.
Sam: How does North Texas compare to other areas of the state or to the country in terms of the number of TB cases?
Dr. Woo: Texas is one of the top four states in the country for tuberculosis because of our proximity to the border.
Sam: How does proximity to the border
Dr. Woo: Because of lack of health care, perhaps areas of high immigration, large urban areas where individuals are immuno-suppressed, any city that has a significant homeless population, any city that has a population of substance abuse problems - those are additional risk factors for the disease.
Dr. Garry Woo is the Medical Director in charge of Tuberculosis Control for Dallas County Health Service.
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