The city of El Paso, Texas, is dealing with two separate outbreaks of tuberculosis, one at a local elementary school and another at a halfway house. The latest data from the city health department, through July 29, shows 57 patients with latent or active TB at the school and 24 at the halfway house. The Examiner spoke with Dr. Andrea Cruz, Research Chief, Pediatric Emergency Medicine, Texas Children’s Hospital in Houston, today regarding tuberculosis and its treatment.
Dr. Cruz told the Examiner that the outbreaks in El Paso are fairly typical of those in the United States. The incidence of TB infections in 2014 was 3 per 100,000 of population, a very low number compared, she said, to some nations where the incidence is in the thousands. Outbreaks in the U.S. generally consist of a small number of active cases of the disease and a much larger number of latent cases.
Latent tuberculosis is when the patient becomes infected but their body’s immune system is able to partially fight off the illness. The patient has no symptoms and may often not know that they have been infected. Dr. Cruz noted that between five and ten percent of these patients will develop active TB in the future.
Patients with latent tuberculosis are not contagious. If their immune system is weakened in some way, their latent TB can activate. An HIV infection is the most common reason for this in many places. In south Texas, though, she pointed to the extremely high rates of Type II diabetes as the primary reason for conversions from latent to active TB.
There are effective treatments for both latent and active TB but there is no vaccine available in the United States. In other countries, the BCG vaccine is routinely given to newborns to protect them while they are infants. The vaccine, Cruz states, has little or no effect on older children or adults. There are many researchers working on an effective vaccine, she added.
Treating active tuberculosis is a long process, involving a course of several antibiotics for a period of six to nine months. TB, according to Todar’s Online Textbook of Bacteriology, is more resistant to antibiotics than many other bacteria due to the high levels of lipids, or fats, in its cell walls. With increasing numbers of cases of tuberculosis resistant to one or more of the usual drugs, treatment of an active infection can be long, costly and, Dr. Cruz pointed out, the risk of serious side effects from the medications is much higher.
Patients with latent TB used to have a similar, though less extensive course of treatment. Compliance among children in completing the course of treatment was as low as fifty percent. A new course of treatment, called 3HP, involves just 12 doses of drugs given once a week. The treatment is indicated for patients with latent tuberculosis who are over two years of age.
Dr. Cruz uses local public health agencies to provide directly observed treatments for latent TB whenever possible. The compliance rate for children with latent TB treated this way is about 95 percent in the Houston area. The use of these resources is limited by their funding and staffing.
Cruz spent some time on a historical perspective of tuberculosis. Before antibiotics, about one third of patients with active TB would recover when treated with fresh air and sunshine at sanitariums. Another third would have chronic TB, remaining infectious, and the remaining patients would died from their illness.
Until quite recently, tuberculosis was a very democratic disease, Dr. Cruz noted. Eleanor Roosevelt died in 1962 from TB, and many other notable, well-to-do personages in American history also had the illness. Since the development of antibiotic treatments for the illness, it has become a disease of the impoverished.
TB is difficult to contact. Cruz pointed to studies from the Navy in World War II that found that about 100 hours of contact with a patient with an active infection were needed to contract TB. The work was done with sailors in the submarine service, where it was easy to determine contact hours. She stated that the variables that cause one patient to become infected and another to not be infected with similar exposures are not known.
As an expert in pediatric tuberculosis, Dr. Cruz believes that all pediatricians should be screening their patients for the risk factors for latent TB. Among them are:
- exposure to an active case of tuberculosis
- chronic cough
- travel overseas
- an HIV infection
- exposure to a person who has been incarcerated
She does not advocate testing all children but does believe that effective screening will identify those at risk of a tuberculosis infection, who can then be tested and treated if necessary.