Tuberculosis Testing Program
TB and Latent TB Infection Overview
TB, or tuberculosis, is a disease caused by bacteria called Mycobacterium tuberculosis. The bacteria can attack any part of your body, but they usually attack the lungs. TB disease was once the leading cause of death in the United States.
In the 1940s, scientists discovered the first of several drugs now used to treat TB. As a result, TB slowly began to disappear in the United States. But TB has come back. Between 1985 and 1992, the number of TB cases increased significantly. The country became complacent about TB and funding of TB programs was decreased. However, with increased funding and attention to the TB problem, we have had a steady decline in the number of persons with TB in Tennessee and across the country. But TB is still a problem; more than 16,000 cases were reported in 2000 in the United States, and 313 cases of TB were reported in Tennessee in 2001.
TB is a disease that is spread from person to person in the air. TB germs (bacteria) are released into the air when someone who has TB sneezes, coughs, speaks, laughs or sings. TB germs are not spread on dishes, drinking glasses or other objects. TB usually affects the lungs, but TB can also affect other parts of the body, such as the brain, throat, kidneys or the spine.
TB in the lungs or throat can be infectious. This means that the bacteria can be spread to other people. TB in other parts of the body, such as the kidney or spine, is usually not infectious.
People with TB disease are most likely to spread it to people they spend time with every day. This includes family members, friends, and coworkers.
Not everyone infected with the TB germ becomes sick. A person with latent TB infection has TB germs in his/her body, but the germs are not active. With latent TB infection, you may not look or feel sick, and you cannot spread the TB germ to others. However, the TB germs can wake up and become active at any time and develop into TB disease. With active TB disease, you can spread the germ to others and you will begin to feel sick with symptoms such as prolonged coughing, fever, weight loss, and fatigue.
Overall, one third of the world’s population is infected with the TB germ, and a person dies of TB every ten seconds. Although we are seeing a decline of TB in the United States, TB still remains one of the world’s deadliest diseases.
We can stop TB. If you have latent TB infection, there are free medications to help prevent you from ever developing active TB and being contagious to others. If you have active TB disease, there are free medications to cure TB. It is very important to take all of the medications to kill the TB germ, to prevent you from spreading TB to your family and friends, and to stop death from TB.
This website will answer many common questions about TB. Please contact your local health department with further questions.
What is latent TB infection?
In most people who breathe in TB bacteria and become infected, the body is able to fight the bacteria to stop them from growing. The bacteria become inactive, but they remain alive in the body and can become active later. This is called latent TB infection. People with latent TB infection:
have no symptoms
don't feel sick
can't spread TB to others
usually have a positive skin test reaction
can develop TB disease later in life if they do not receive treatment for latent TB infection
Many people who have latent TB infection never develop TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease. But in other people, especially people who have weak immune systems, the bacteria become active and cause TB disease.
What is TB disease?
TB bacteria become active if the immune system can't stop them from growing. The active bacteria begin to multiply in the body and cause TB disease. Some people develop TB disease soon after becoming infected, before their immune system can fight the TB bacteria. Other people may get sick later, when their immune system becomes weak for some reason.
Babies and young children often have weak immune systems. People infected with HIV, the virus that causes AIDS, have very weak immune systems. Other people can have weak immune systems, too, especially people with any of these conditions:
- substance abuse
- diabetes mellitus
- cancer of the head or neck
- leukemia or Hodgkin's disease
- severe kidney disease
- low body weight
- certain medical treatments (such as steroid treatment or organ transplants)
Symptoms of TB depend on where in the body the TB bacteria are growing. TB bacteria usually grow in the lungs. TB in the lungs may cause:
- a bad cough that lasts longer than two weeks
- pain in the chest
- coughing up blood or sputum (phlegm from deep inside the lungs)
Other symptoms of TB disease are:
- weakness or fatigue
- weight loss
- no appetite
- sweating at night
Latent TB Infection
How can I get tested for TB?
A TB skin test is the only way to find out if you have latent TB infection. You can get a skin test at the health department or at your doctor's office. You should get tested for TB if:
- you have spent time with a person with known or suspected to have TB disease
- you have HIV infection or another condition that puts you at high risk for TB disease
- you think you might have TB disease
- you are from a country where TB disease is very common (most countries in Latin America and the Caribbean, Africa, Asia, Eastern Europe, and Russia)
- you inject drugs
- you live somewhere in the U.S. where TB disease is more common (homeless shelters, migrant farm camps, prisons and jails, and some nursing homes)
A health care worker can give you the TB skin test. The health care worker will inject a small amount of testing fluid (called tuberculin) just under the skin on the lower part of your arm. After two or three days, the health care worker will measure your reaction to the test. You may have a small bump where the tuberculin was injected. The health care worker will measure this bump and tell you if your reaction to the test is positive or negative. A positive reaction usually means that you have latent TB infection.
If you have a positive reaction to the skin test, your doctor or nurse may do other tests to see if you have TB disease. These tests usually include a chest x-ray and a test of the phlegm you cough up. Because the TB bacteria may be found somewhere besides your lungs, your doctor or nurse may check your blood or urine, or do other tests. If you have TB disease, you will need to take medicine to cure the disease.
If you have recently spent time with someone with infectious TB, your skin test reaction may not be positive yet. You may need a second skin test 10 to 12 weeks after the last time you spent time with the infectious person. This is because it can take several weeks after infection for your immune system to be able to react to the TB skin test. If your reaction to the second test is negative, you probably do not have latent TB infection.
What if I have been vaccinated with BCG?
BCG is a vaccine for TB. This vaccine is not widely used in the United States, but it is often given to infants and small children in other countries where TB is common. BCG vaccine does not always protect people from TB.
If you were vaccinated with BCG, you may have a positive reaction to a TB skin test. This reaction may be due to the BCG vaccine itself or to latent TB infection. But your positive reaction probably means that you have latent TB infection if:
- you recently spent time with a person who has TB disease
- you are from an area of the world where TB disease is very common (most countries in Latin America and the Caribbean, Africa, Asia, Eastern Europe, and Russia)
- you spend time where TB is common (homeless shelters, drug-treatment centers, health care clinics, jails, prisons)
If I have TB infection, how can I keep from developing TB disease?
Many people who have latent TB infection never develop TB disease. But some people who have latent TB infection are more likely to develop TB disease than others. These people are at high risk for TB disease. They include:
- people with HIV infection
- people who became infected with TB bacteria in the last two years
- babies and young children
- people who inject drugs
- people who are sick with other diseases that weaken the immune system
- elderly people
- people who were not treated correctly for TB in the past
If you have latent TB infection, you need to take medicine to keep from developing TB disease. This is called treatment for latent TB infection. There are many treatment options. You and your health care provider must decide which treatment is best for you.
The medicine usually used for the treatment of latent TB infection is a drug called isoniazid or INH. INH kills the TB bacteria that are in the body. If you take your medicine as prescribed, treatment for latent TB infection will keep you from ever developing TB disease.
Most people must take INH for at least six to nine months. Children and people with HIV infection may need to take INH for a longer time.
Sometimes people are given treatment for latent TB infection even if their skin test reaction is not positive. This is often done with infants, children, and HIV-infected people who have recently spent time with someone with infectious TB disease. This is because they are at very high risk of developing serious TB disease soon after they become infected with TB bacteria.
It is important that you take all the pills prescribed for you so that your treatment for latent TB infection is effective. If you start taking INH, you will need to see your doctor or nurse on a regular schedule. He or she will check on how you are doing.
People who have latent TB infection but do not receive treatment for latent TB infection need to know the symptoms of TB. If they develop symptoms of TB disease later on, they should see a doctor right away.
What if I have HIV infection?
A person can have latent TB infection for years without any signs of disease. But if that person's immune system gets weak, the infection can quickly turn into TB disease. Also, if a person who has a weak immune system spends time with someone with infectious TB, he or she may become infected with TB bacteria and quickly develop TB disease.
Because HIV infection weakens the immune system, people with latent TB infection and HIV infection are at very high risk of developing TB disease. All HIV-infected people should be given a TB skin test to find out if they have latent TB infection. If they have latent TB infection, they need treatment for latent TB infection as soon as possible to prevent them from developing TB disease. If they have TB disease, they must take medicine to cure the disease.
TB disease can be prevented and cured, even in people with HIV infection.
How is TB disease treated?
There is good news for people with TB disease! TB disease can almost always be cured with medicine. But the medicine must be taken as the doctor or nurse tells you.
The most common drugs used to fight TB are:
- isoniazid (INH)
If you have TB disease, you will need to take several different drugs. This is because there are many bacteria to be killed. Taking several drugs will do a better job of killing all of the bacteria and preventing them from becoming resistant to the drugs.
If you have TB of the lungs or throat, you are probably infectious. You need to stay home from work or school so that you don't spread TB bacteria to other people. After taking your medicine for a few weeks, you will feel better and you may no longer be infectious to others. Your doctor or nurse will tell you when you can return to work or school.
Having TB should not stop you from leading a normal life. When you are no longer infectious or feeling sick, you can do the same things you did before you had TB. The medicine that you are taking should not affect your strength, sexual function, or ability to work. If you take your medicine as your doctor or nurse tells you, the medicine will kill all the TB bacteria. This will keep you from becoming sick again.
Why do I need to take TB medicine regularly?
TB bacteria die very slowly. It takes at least six months for the medicine to kill all the TB bacteria. You will probably start feeling well after only a few weeks of treatment. But beware! The TB bacteria are still alive in your body. You must continue to take your medicine until all the TB bacteria are dead, even though you may feel better and have no more symptoms of TB disease.
If you don't continue taking your medicine or you aren't taking your medicine regularly, this can be very dangerous. The TB bacteria will grow again and you will remain sick for a longer time. The bacteria may also become resistant to the drugs you are taking. You may need new, different drugs to kill the TB bacteria if the old drugs no longer work. These new drugs must be taken for a longer time and usually have more serious side effects.
If you become infectious again, you could give TB bacteria to your family, friends, or anyone else who spends time with you. It is very important to take your medicine the way your doctor or nurse tells you.
How can I keep from spreading TB?
The most important way to keep from spreading TB is to take all your medicine, exactly as directed by your doctor or nurse. You should also keep all of your clinic appointments! Your doctor or nurse needs to see how you are doing. You may need another chest x-ray or a test of the phlegm you may cough up. These tests will show whether the medicine is working. They will also show whether you can still give TB bacteria to others. Be sure to tell the doctor about anything you think is wrong.
If you are sick enough with TB to go to a hospital, you may be put in a special room. These rooms use air vents that keep TB bacteria from spreading. People who work in these rooms must wear a special face mask to protect themselves from TB bacteria. You must stay in the room so that you will not spread TB bacteria to other people. Ask a nurse if you need anything that is not in your room.
If you are infectious while you are at home, there are certain things you can do to protect yourself and others near you. Your doctor may tell you to follow these guidelines to protect yourself and others:
The most important thing is to take your medicine.
Always cover your mouth with a tissue when you cough, sneeze, or laugh. Put the tissue in a closed paper sack and throw it away.
Do not go to work or school. Separate yourself from others and avoid close contact with anyone. Sleep in a bedroom away from other family members.
Air out your room often to the outside of the building (if it is not too cold outside). TB spreads in small closed spaces where air doesn't move. Put a fan in your window to blow out (exhaust) air that may be filled with TB bacteria. If you open other windows in the room, the fan also will pull in fresh air. This will reduce the chances that TB bacteria stay in the room and infect someone who breathes the air.
Remember, TB is spread through the air. People cannot get infected with TB bacteria through handshakes, sitting on toilet seats, or sharing dishes and utensils with someone who has TB.
After you take medicine for about two or three weeks, you may no longer be able to spread TB bacteria to others. If your doctor or nurse agrees, you will be able to go back to your daily routine. Remember, you will get well only if your take your medicine exactly as your doctor or nurse tells you.
Think about people who may have spent time with you, such as family members, close friends, and coworkers. The local health department may need to test them for latent TB infection. TB is especially dangerous for children and people with HIV infection. If infected with TB bacteria, these people need preventive therapy right away to keep from developing TB disease.
What is multidrug-resistant TB (MDR TB)?
When TB patients do not take their medicine as prescribed, the TB bacteria may become resistant to a certain drug. This means that the drug can no longer kill the bacteria.
Drug resistance is more common in people who:
- have spent time with someone with drug-resistant TB disease
- do not take their medicine regularly
- do not take all of their prescribed medicine
- develop TB disease again, after having taken TB medicine in the past
- come from areas where drug-resistant TB is common
Sometimes the bacteria become resistant to more than one drug. This is called multidrug-resistant TB, or MDR TB. This is a very serious problem. People with MDR TB disease must be treated with special drugs. These drugs are not as good as the usual drugs for TB and they may cause more side effects. Also, some people with MDR TB disease must see a TB expert who can closely observe their treatment to make sure it is working.
People who have spent time with someone sick with MDR TB disease can become infected with TB bacteria that are resistant to several drugs. If they have a positive skin test reaction, they may be given preventive therapy. This is very important for people who are at high risk of developing MDR TB disease, such as children and HIV-infected people.
Glossary of Terms Related to TB
BCG - a vaccine for TB named after the French scientists Calmette and Guérin. BCG is not widely used in the United States, but it is often given to infants and small children in other countries where TB is common.
Cavity - a hole in the lung where TB bacteria have eaten away the surrounding tissue. If a cavity shows up on your chest x-ray, you are more likely to cough up bacteria and be infectious.
Chest x-ray - a picture of the inside of your chest. A chest x-ray is made by exposing a film to x-rays that pass through your chest. A doctor can look at this film to see whether TB bacteria have damaged your lungs.
Contact - a person who has spent time with a person with infectious TB.
Culture - a test to see whether there are TB bacteria in your phlegm or other body fluids. This test can take 2 to 4 weeks in most laboratories.
Directly observed therapy (DOT) - a way of helping patients take their medicine for TB. If you get DOT, you will meet with a health care worker every day or several times a week. You will meet at a place you both agree on. This can be the TB clinic, your home or work, or any other convenient location. You will take your medicine at this place.
Extrapulmonary TB - TB disease in any part of the body other than the lungs (for example, the kidney or lymph nodes).
HIV infection - infection with the human immunodeficiency virus, the virus that causes AIDS (acquired immunodeficiency syndrome). A person with both latent TB infection and HIV infection is at very high risk for TB disease.
Infectious TB - TB disease of the lungs or throat, which can be spread to other people.
Infectious person - a person who can spread TB to others because he or she is coughing TB bacteria into the air.
INH or isoniazid - a drug used to prevent TB disease in people who have latent TB infection. INH is also one of the five drugs often used to treat TB disease.
Latent TB infection - a condition in which TB bacteria are alive but inactive in the body. People with latent TB infection have no symptoms, don't feel sick, can't spread TB to others, and usually have a positive skin test reaction. But they may develop TB disease later in life if they do not receive treatment for latent TB infection.
Miliary TB - TB disease that has spread to the whole body through the bloodstream.
Multidrug-resistant TB (MDR TB) - TB disease caused by bacteria resistant to more than one drug often used to treat TB.
M. tuberculosis - bacteria that cause latent TB infection and TB disease.
Negative - usually refers to a test result. If you have a negative TB skin test reaction, you probably do not have latent TB infection.
Positive - usually refers to a test result. If you have a positive TB skin test reaction, you probably have latent TB infection.
Pulmonary TB - TB disease that occurs in the lungs, usually producing a cough that lasts longer than 2 weeks. Most TB disease is pulmonary.
Resistant bacteria - bacteria that can no longer be killed by a certain drug.
TB skin test - a test that is often used to detect latent TB infection. A liquid called tuberculin is injected under the skin on the lower part of your arm. If you have a positive reaction to this test, you probably have latent TB infection.
Treatment for latent TB infection - treatment for people with latent TB infection that prevents them from developing TB disease.
Smear - a test to see whether there are TB bacteria in your phlegm. To do this test, lab workers smear the phlegm on a glass slide, stain the slide with a special stain, and look for any TB bacteria on the slide. This test usually takes 1 day.
Sputum - phlegm coughed up from deep inside the lungs. Sputum is examined for TB bacteria using a smear; part of the sputum can also be used to do a culture.
TB disease - an illness in which TB bacteria are multiplying and attacking different parts of the body. The symptoms of TB disease include weakness, weight loss, fever, no appetite, chills, and sweating at night. Other symptoms of TB disease depend on where in the body the bacteria are growing. If TB disease is in the lungs (pulmonary TB), the symptoms may include a bad cough, pain in the chest, and coughing up blood.
Tuberculin - a liquid that is injected under the skin on the lower part of your arm during a TB skin test. If you have latent TB infection, you will probably have a positive reaction to the tuberculin.
Adapted from Center for Disease Control’s web-site: www.cdc.gov
Last Reviewed: August 13, 2002
Centers for Disease Control & Prevention
National Center for HIV, STD, and TB Prevention
Division of Tuberculosis Elimination