Ask The Expert // Tuberculosis

July 10, 2008|By Holly Selby

Mimi suffers from tuberculosis in the opera La Boheme, but in reality, there is little that's romantic about the disease.

It is the second-leading cause of death from infection in the world (though not in the United States), says Dr. Richard E. Chaisson, professor of medicine, epidemiology and international health at the Johns Hopkins School of Medicine and founding director of the Johns Hopkins Center for Tuberculosis Research.

Worldwide, the highest number of TB cases and deaths in recorded history will occur this year, according to Hopkins' Department of Medicine Web site. The increased incidence and the increase in drug-resistant strains of the disease are being fueled, in part, by the spread of HIV/AIDS, which suppress the immune system.

What is tuberculosis?

Tuberculosis is a disease caused by a bug called Mycobacterium tuberculosis that has been around for many centuries and can affect any part of the body. Tuberculosis, or TB, can spread to other parts of the body, such as lymph nodes, brain, spinal cord, bones, kidneys and virtually any other part of the body. But it primarily affects the lungs and causes a form of chronic pneumonia that, left untreated, can be fatal.

What are the symptoms of tuberculosis?

Most people who have TB experience a cough and, many times, this cough produces sputum that has blood in it. It also frequently causes chest pain, weight loss, fever and a general feeling of malaise or being unwell.

Depending upon whether other parts of the body are involved, the patient also may have symptoms related to those sites, like headache or back pain, or passing blood in the urine.

How common is this disease?

Well, tuberculosis is the second-leading cause of death by infection in the world, and in many parts of the world, the rates are very high. Here in the United States, the incidence has gone down dramatically over the last 15 years; currently, we are at our lowest rates ever in this country, at about five cases per 100,000 population. The world average is about 130 per 100,000.

Half of the cases of TB that occur in the U.S. occur in people who were born elsewhere and have moved here.

What about globally?

Worldwide, TB is a huge problem. Rates in Africa have more than tripled in the past 15 years, and rates in Eastern Europe have doubled. In Asia and Latin America, the rates are high but stable, or even slightly declining.

How is it spread?

Tuberculosis is spread through the air by people who are sick with it and who cough and expel the tuberculosis organism into the air, where it floats around and gets inhaled by someone else. The organism can remain in the air for several hours.

Now, most people who become infected with tuberculosis don't get sick with it because, over the centuries, our bodies have developed immune defenses to control the infection. But people who have a weakened immune system or who are taking certain medicines are more susceptible. For example, people who have HIV or AIDS, who have cancer, who are taking drugs like steroids that suppress the immune system or who have diabetes are more susceptible.

How is tuberculosis diagnosed?

TB usually is suspected when symptoms are present and X-rays show the pneumonia that the infection causes, and then is confirmed by cultures of the sputum or other tissues that might be involved. The most important step is to suspect TB and get the culture.

Once diagnosed, what is the treatment?

Tuberculosis is typically treated with antibiotics that are given for six months. We initially use four antibiotics that rapidly bring the infection under control and then continue with just two antibiotics that eliminate the infection.

It is important to continue [taking the medicines] for all six months, or the patient can run the risk of relapse.

Some strains of TB are drug-resistant, and then we have to rely on antibiotics that are less effective and more toxic, and treat the disease for 18 to 24 months. In the United States, more than 95 percent of TB can be treated with the standard six-month antibiotics; resistant strains are not very prevalent here.

What if TB goes untreated?

If untreated, a majority of patients will eventually die. About one-fourth of patients may spontaneously clear the infection after a period of weeks or months. ... The remainder will be chronically ill with TB, and that may go on for years.

What is new in research into TB?

The current treatment of TB requires six months of antibiotics, and that is a very long time for people to take medicines, especially when they feel better. So, we have been working on more potent treatments that will shorten the length of time treatment takes.

My colleagues here at Hopkins have conducted experiments in mice with TB that show that the new drugs could shorten the time required to cure TB to three or four months. Now we are doing human clinical trials to see whether these new treatments will be successful.

Why do the protagonists of operas frequently have TB?

It is a disease that, particularly in the 1800s, had some romanticism attached to it. It was thought to be the disease of suffering lovers and starving artists and made its way into a number of operas and other works. But I can guarantee you that if Mimi in La Boheme had TB, she wouldn't have been able to sing any of those arias.

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