Tuberculosis (TB) is a bacterial infection caused by Mycobacterium tuberculosis that is becoming increasingly common in the Seattle area. I have recently talked to an infectious disease specialist who has seen much more documented TB on the “eastside” of Seattle recently. It can cause serious, life-threatening infections of the lung and can spread to the brain, the bones and kidneys. We have many people who work and visit from countries where TB is more prevalent and they are bringing this illness with them.
Symptoms of latent TB: No symptoms may be present – it is detected by a skin or blood test.
Symptoms of active TB: May include fever, night sweats, cough (sometimes coughing up blood), weight loss, pleuritic chest pain, fatigue, joint pain, and sore throat.
Signs of active TB: The most common abnormality found on chest x-ray is abnormal lymph nodes of the upper lung area.
Transmission of TB in health care facilities is a very important concern because we treat patients in our clinics and hospital systems who are infected and healthcare workers or other patients who are near the infected patients could potentially get infected. The treatment for the infection often includes taking antibiotics every day for 9 months.
Worldwide, tuberculosis is a leading cause of death. Identifying people and treating those who are infected, but have not yet developed active TB, can prevent the spread of the disease into the community.
At risk groups:
1) Foreign-born persons from areas with high TB prevalence (especially those who have arrived in the US from endemic areas less than 5 years ago) or individuals to travel frequently to these areas.
2) Homeless patients
3) Residents of correctional facilities, nursing homes or homeless shelters
4) The elderly- because the have been alive during a time of higher TB presence in the US.
5) Health care workers who serve patients at high risk in the US
6) Health care workers who volunteer in regions where TB is endemic
7) Medically underserved and/or low income patients
8) Infants, children and adolescents exposed to adults in high risk categories.
Transmission: Particles of TB are transmitted via person-to-person when we inhale vapors that have been exhaled by infected patients. Coughing facilitates the formation of these particles. Patients with active, and untreated infection in their respiratory systems can spread the disease.
Multi Drug Resistant TB (MDR TB): There is growing concern about tuberculosis that has become resistant to multiple drugs, including isoniazid, rifampin, ethambutol and streptomycin which are the main medications used to treat TB.
Active vs. Latent TB infections: Understanding TB infection can be confusing, even for healthcare providers.
Example: An individual who has been exposed to a patient with active TB can become infected, but they usually do not immediately develop symptoms. They are unaware of their infection, unless they are tested by a TB skin test or a blood test. Healthcare workers undergo this screening procedure every year since we are at higher risk of becoming infected than the average population. In this example the infected person has a latent TB infection and is not actively spreading the disease to others. The bacteria are contained within the infected persons body and their immune system attempts to contain the bacteria and fight it off.
These bacteria are very strong however, and can potentially evade the immune system in some people and cause an active infection. Active TB may result if the latent TB infection is not treated and this occurs in 5-10 percent of people with a latent TB infection. If the individual develops an active TB infection, symptoms will be present and the bacteria can be spread to non-infected people.
When someone with latent TB develops active TB, this is called reactivation and may occur if the individual’s immune system becomes weakened and is not able to contain the dormant bacteria. The biggest risk for developing the reactivation TB is within the first two years after the initial infection. It can also occur with other diseases that lower the person’s immune system such as HIV, diabetes and those who take long term steroid or chemotherapy medications.
Vaccine for TB (BCG vaccine): A vaccine is given in many countries to prevent infection with TB. Unfortunately this vaccine offers very little protection, if any against TB beyond early childhood. BCG is not used to prevent TB in the US.
Diagnosing latent TB: A skin test called PPD is the most common test for diagnosing TB. If a person has a new infection, the test usually becomes positive about 4-10 weeks after exposure. Skin tests are performed by injecting a small amount of solution just underneath the skin of the forearm. The solution contains bacteria that are inactivated – so they can’t cause infection. People that have been infected with the TB bacteria develop a skin reaction that is red and swollen at this site. The skin test has to be checked 48-72 hours after the injection by a trained healthcare worker. If the test is positive, a physical exam must be completed to decide whether the individual has active TB or latent TB. A chest x-ray is also usually performed.
Blood tests for TB: There are blood tests available in some areas to test for TB infection. These tests may simplify testing because they do not require the person to make a return trip to read the test reaction. The blood tests are generally explained as being more accurate that then skin tests, however they are more expensive.
Treatment for latent TB: If someone has a positive TB skin test or blood test, and they do not have the active disease, they are usually treated with medication to kill the bacteria contained within the infected persons body. Treating this latent infection reduces the risk of the infection progressing to active TB later.
A) Isoniazid (INH) is a pill taken once a day for either 3 or 9 months. Missing days or discontinuing the medication may not prevent active TB. Isoniazid can cause elevation of your liver enzymes, so it is important to have your blood work monitored if you take this medication.
B) Rifampin (RIF) is taken as two capsules every day for either 3 or 4 months. There is a reaction with other medications in the body such as birth control pills, patches, blood thinners, and many other medications so it is important to discuss possible reactions with your doctor. Rifampin will turn your urine orange and may stain contact lenses an orange color. It can also cause elevation in liver enzymes, so it is important to have your blood monitored if taking this medication.
C) Rifapentine (RPT) taken with isoniazid usually for 3 months
The CDC has listed 4 different treatment regimens for Latent TB Infection if the organism is not felt to be drug-resistant:
1) Isoniazid: Taken daily for 9 months or twice a week with direct observation (76 doses)
2) Isoniazid: Taken daily for 6 months or twice a week with direct observation (52 doses)
3) Isoniazid and Rifapentine taken once a week for 3 months with direct observation (12 doses)
4) Rifampin taken daily for 4 months (120 doses)
Patient monitoring: It is important for anyone taking these medications to be monitored for signs of liver toxicity. This is extremely uncommon but is serious. Signs of liver injury can include unexplained fatigue, loss of appetite, nausea, vomiting, jaundice (yellowing of the skin or whites of the eyes), or abdominal pain.
Active Tuberculosis: When active TB occurs, symptoms are usually present and cause the individual to be sick. If there is signs of TB on chest x-ray, then cultures of mucus which is coughed up from the patient is collected and tested for the bacteria. These cultures can take 2 months to detect whether the bacteria is present. During this time the patient is usually taking 4 different antibiotics. We use multiple different antibiotics in efforts to prevent the bacteria from becoming resistant to one (or more) of the antibiotics.
Public Health Concerns: US law requires that anyone with active TB be reported to the health department because the disease can easily be spread. The health department will work with the patient and their doctor to make sure that they are treated safely. Directly observed therapy (DOT) is often used by public health to ensure the medications are taken as prescribed. A nurse will watch the patient take the medication.
This document is for informational purposes only, and should not be considered medical advice for any individual patient. If you have questions please contact your medical provider.
I hope that you have found this information useful. Wishing you the best of health,
Scott Rennie, DO
References: http://www.cdc.gov/tb/topic/treatment/ltbi.htm – accessed January 2013