February 2010

Extensively-drug resistant tuberculosis (XDR TB) is a strain of TB resistant to at least isoniazied and rifampin among the first-line anti-TB drugs and to any fluoroquinolone and at least one of the three second-line injectable drugs: capreomycin, kanamycin, or amikan.¹ XDR TB has emerged worldwide as a threat to public health and TB control, raising concerns of a future epidemic of virtually untreatable TB.²

It is speculated that XDR TB emerged from multidrug-resistant tuberculosis (MDR TB) as that strain is also resistant to the primary drugs isoniazid and rifampin. Resistance to one or several forms of treatment occurs when the bacteria develops the ability to withstand antibiotic attack and relays that ability to its offspring. Since that entire strain of bacteria inherits the capacity to resist the effects of the various treatments, resistance can spread from one person to another. On an individual basis, however, inadequate treatment or improper use of the anti-tuberculosis medications remains an important cause of drug-resistant tuberculosis. Drug-resistant TB is difficult and costly to treat and can be fatal.³

• In 2006, 644 people died of tuberculosis, a slight decrease from the 648 deaths in 2005.⁴
• From 1993 to 2006, 49 cases of XDR TB were reported in the US, spread across nine states and one city.⁵ Two more cases were diagnosed in 2007, and provisional data indicates that four XDR TB cases were reported in 2008.⁶
• The number of XDR TB cases among foreign-born persons was almost the same during 1993-1999 and 2000-2006 (12 and 13, respectively), but the percentage among this group increased from 39 percent to 76 percent as the number of XDR TB cases among U.S.-born persons declined.⁷
• Among non-Hispanic blacks, both the number and percent of total cases of XDR TB decreased from 1993-1999 to 2000-2006, from 9 (32%) to 2 (12%). However, this trend was reversed among Asians as the number and percent of cases increased from 3 (9%) to 7 (41%) over these two time periods.⁸
• In 2007, a total of 125 cases of MDR TB were reported, which was a slight increase from the 116 cases reported in 2006.⁹
• Only 18.4 percent of primary MDR TB cases were in U.S. born persons. The proportion of MDR TB cases continues to disproportionately affect foreign-born persons in the United States. This group accounted for 26 percent of MDR TB cases in 1993, but 81.6 percent of such cases in 2007.¹⁰
• It is important to understand that there is a difference between being infected with TB and having TB disease. Someone who is infected with TB has the TB germs, or bacteria, in his/her body. The body's defenses, though, are protecting them from the germs, and they are not sick and cannot spread TB. This is known as latent tuberculosis. However, if a person infected with latent TB does not seek treatment they are at risk of developing active TB.¹¹
• The AIDS epidemic is considered a major factor in the increase of TB cases.  HIV's suppression of the immune system both opens the door to new active infection and permits activation of latent TB. One-third of the increase in global TB cases over the last five years can be attributed to the HIV epidemic.¹²
• Symptoms of active TB disease include prolonged coughing (sometimes including coughing up of blood), repeated night sweats, unexplained weight loss, loss of appetite, fever, chills, and general lethargy.  Because these signs may be indicative of other diseases as well, a person must consult a physician to determine the cause of these symptoms.
• The simplest way to find out if you have a TB infection is to get a TB skin test, which is widely available at clinics or at a doctors' office. The preferred method is the Mantoux test, which is used for both screening and diagnosis. This TB tests requires a small amount of testing material is injected under the very top layers of skin on the forearm. In 48 to 72 hours the test is read by a trained person, usually a nurse or doctor. If the test is significant, then you probably have TB infection and the doctor will run more tests, such as a chest x-ray, to determine whether you have active TB disease. In some groups, such as the elderly or those with impaired immunity, the skin test may not be significant in the presence of TB infection.¹³
• The recommended length of drug therapy for most types of TB is 6 to 9 months.¹⁴ Treatment for MDR TB is expensive and involves drug therapy over many months or years. Even with the longer course of treatment, the cure rate for MDR TB is approximately 50 percent, compared to over 90 percent for non-resistant strains of TB. XDR TB treatment is successful approximately 30 percent of the time for patients without compromised immune systems; it is even lower for those with compromised immune systems (such as those with HIV/AIDS).¹⁵
• In 2006, 83.5 percent of TB patients completed therapy within 1 year, which was below the Health People 2010 target of 90 percent. Reasons patients did not complete therapy included moving, being lost track of, refusing to continue treatment, and dying.¹⁶ During 1993 to 2002, patients with XDR TB were 64 percent more likely to die or have treatment failure.¹⁷
• Because it is difficult for some people to successfully complete their tuberculosis treatment, several innovations have been developed. The use of incentives and enablers has been popular with health departments and TB treatment centers. Examples include free transport to centers or food coupons which are given to patients each time they appear at the clinic or doctor's office for treatment. Incentives and enablers are combined with the use of directly observed therapy (DOT). DOT is a system of treatment in which the patient is administered his or her medication by a nurse or health worker whom "observes" the medication is taken.¹⁸

For more information on tuberculosis, please review the Tuberculosis chapter from Lung Disease Data 2008 and the Tuberculosis Morbidity and Mortality Trend Report in the Data and Statistics section of our website at www.lung.org or call the American Lung Association at 1-800-LUNG-USA (1-800-586-4872).

1. Centers for Disease Control and Prevention. Trends in Tuberculosis – United States, 2008. Morbidity and Mortality Weekly Report. March 20, 2009; 58(10):249–53.

2. Centers for Disease Control and Prevention. Emergence of Mycobacterium Tuberculosis with Extensive Resistance to Second-Line Drugs — Worldwide, 2000–2004. Morbidity and Mortality Weekly Report. March 24, 2006; 55(11):301–5.

3. Ibid.

4. Centers for Disease Control and Prevention. National Center for Health Statistics. National Vital Statistics Reports. Deaths. Final Data for 2005. April 24, 2008; 56(10).

5. Centers for Disease Control and Prevention. Extensively Drug-Resistant Tuberculosis – United States, 1993--2006. Morbidity and Mortality Weekly Report. March 23, 2007; 57(11):281–5.

6. Centers for Disease Control and Prevention. Trends in Tuberculosis – United States, 2008. Morbidity and Mortality Weekly Report. March 20, 2009; 58(10):249–53.

7. Centers for Disease Control and Prevention. Extensively Drug-Resistant Tuberculosis – United States, 1993--2006. Morbidity and Mortality Weekly Report. March 23, 2007; 57(11):281–5.

8. Ibid.

9. Centers for Disease Control and Prevention. Trends in Tuberculosis – United States, 2008. Morbidity and Mortality Weekly Report. March 20, 2009; 58(10):249–53.

10. Ibid.