Recent reports of Tuberculosis, a disease long thought of as a ‘thing of the past’ have sparked many questions among the public – What is it? Will I catch it? How can I prevent it?
Heath Talk asked pediatric infectious disease expert Mark R. Schleiss, M.D., professor within the University of Minnesota Medical School, to provide more information about this scary sounding infection.
What is Tuberculosis and how is it contracted?
Tuberculosis (TB) is a bacterial infection caused by an organism known as Mycobacterium tuberculosis. It is an infection as old as humankind. By some estimates, before the 19th century, one in seven people in human history died of TB. Since the beginning of the 19th century, more than a billion people have died from the disease.
TB is spread from person-to-person, almost always by inhaling respiratory secretions associated with coughing or breathing. Except for one form called “endobronchial tuberculosis,” it is not as contagious in children as it is in adults.
If someone is on treatment for tuberculosis, they are no longer contagious.
TB is often thought of as “a thing of the past.” Why has a new case(s) resurfaced?
TB could better characterized as a disease that is “forgotten but not gone.” It never vanished or disappeared from the landscape. With better surveillance, public health measures, nutrition, improved standards of living, and prophylactic medications for individuals with exposure and/or early infection with tuberculosis, we saw dramatic decreases in the disease in the US in the last 50-75 years. But, tuberculosis was never eradicated. It is common for cases to surface periodically in schools, hospitals, and other public places. The continued existence of human reservoirs of TB underscores the need for public health surveillance and screening programs.
How can people prevent the transmission of TB?
The most effective way to prevent transmission is to periodically be screened if you are in a high-risk profession or if you are potentially exposed to individuals with infection. Health care professionals, for example, often require annual screening for the disease, which can be accomplished by a simple blood test or skin test. This is important because when you first acquire a TB infection, you are usually healthy and have no symptoms. The infection can be “latent” – meaning the infection can be present without symptoms. Individuals who have acquired TB are at high risk of having their latent infection transform into an active, contagious infection. Once the infection is active, the individual usually has a cough, and can spread the bacteria to others. Therefore, aggressive screening of high-risk individuals, and a form of treatment called “prophylactic” treatment, is the best way to prevent transmission. Prophylactic treatment is antibiotic treatment given to someone who is infected, but asymptomatic. A chest X-ray is often helpful in assessing the status of TB infection. Prophylactic treatment is known to prevent progression to active, contagious disease.
What role do vaccines play in stopping TB? How effective is TB vaccine?
A vaccine for TB exists. In fact, it’s the most widely used vaccine in the world today! We do not use it in the US (with rare exceptions). One reason is that the prevalence of tuberculosis is low in the US compared to the developing world. A second reason is that the vaccine is not very effective. The vaccine does not prevent acquisition or spread of tuberculosis. However, the vaccine when given to very young infants is able to confer enough immunity to prevent development of life-threatening forms of tuberculosis. Thus, since it saves lives, use of the vaccine in newborns is warranted in parts of the world where tuberculosis is common. We need a better vaccine – one that would completely prevent infection and eventually wipe tuberculosis off the map (as was accomplished with an effective smallpox vaccine). Improved vaccines for TB are being studied by many scientists around the world. This is a high-priority area for future research.
Can TB be transmitted even if people have the vaccine?
The vaccine unfortunately does not prevent infection and, with the exception of severe life-threatening forms of TB in babies, the vaccine does not even prevent disease. Therefore, it’s critical that someone exposed to TB, or who presents with symptoms and signs of disease compatible with TB, be evaluated for infection and considered as a candidate for treatment – irrespective of their vaccination history.