Tuberculosis

Latent vs. Active TB

Tuberculosis is caused by Mycobacterium tuberculosis. This disease is commonly known as TB. The bacteria affect patients usually by attacking their lungs causing the common symptoms that one thinks of when they think of TB. The bacteria can affect any part of the body besides the lungs. TB is spread through the air (i.e. breathing, sneezing, coughing, speaking, etc.) and cannot be contracted through daily activities such as touching or sharing food.

TB can infect a person in two different ways. The first way is active TB; this form is the most people think of as TB, because Active TB is more noticeable. Patients with active TB have noticeable symptoms such as coughing for more than three weeks or unexplained weight loss. The other form of TB is latent TB. Latent TB occurs when a person come into contact with the TB virus and shows no obvious signs of illness. This makes latent TB harder to diagnose. Latent TB is the most common form of TB There are many differences and a few similarities between active TB and latent TB. Tuberculosis is difficult to diagnose because doctors are more likely to look for more common illnesses. A lot of times TB is diagnosed too late or even not at all. The laws regarding reporting TB require Active TB to be reported but Latent TB may go unreported until it becomes active. There are also a lot of people who may not know that they are infected with TB and may never know unless it becomes active.

Latent TB is more difficult to diagnose than active TB. Latent TB is only diagnosable by a blood test. A person with active TB will have a positive sputum test, skin test, blood test, and chest x-ray. Latent TB occurs in about 90% of people infected with TB. In the state of Missouri there are about 3000 reported cases of Latent TB. There are no laws requiring latent TB to be reported so this number maybe larger. On average about 10% of latent TB cases will progress to becoming Active TB. Active TB is contagious and can cause serious side effects if not caught soon enough. Latent TB is not contagious but due to the risk of it later becoming active it still should be treated.

The risk of being infected with TB, latent or active, is higher in patients with a compromised immune system. A person’s risk of coming in contact with TB is also much higher due to latent TB. Because Latent TB has no signs or symptoms and is not contagious it is harder to identify. This makes identifying active TB more difficult later. On average about 3%-5% cases of latent TB will turn active with in a year of contacting the disease. Later your chances of developing active TB increase to 5%-15%. Latent TB will take advantage of a weakened immune system and turn into active TB. If Active TB is not caught early enough it can become deadly.

Bibliography

Centers for Disease Control and Prevention. (2010, November 24). CDC- Tuberculosis. Retrieved October 15th, 2010, from Centers for Disease Control and Prevention: http://www.cdc.gov/tb/ Essig, M. G. (2009, April 23). Tuberculosis (TB) - Topic Overview: WebMD. Retrieved October 15, 2010, from WebMD: http://www.webmd.com/lung/tc/tuberculosis-tb-topic-overview Mayo Clinic Staff. (2009, January 28). Tuberculosis- Mayo Clinic. Retrieved October 15th, 2010, from Mayo Clinic: http://www.mayoclinic.com/health/tuberculosis/DS00372