Questions and Answers 

About Tuberculosis 

2009

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

Q&A About TB | i

Questions and Answers 

About Tuberculosis

2009

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention

Division of Tuberculosis Elimination
ii | Q&A About TB
Q&A About TB | iii

CONTENTS

For definitions of common terms related to TB, see the glossary at the back of this booklet (page 16).

INTRODUCTION

What is TB?

Why is TB still a problem in the United States?

How is TB spread?

What is latent TB infection?

What is active TB disease?

LATENT TB INFECTION

Should I get tested for TB?

What are the tests for TB infection?

What if I have a positive test for TB infection?

What if I have been vaccinated with BCG?

If I have latent TB infection, how can I keep from developing active TB disease?

What if I have HIV infection?

If I was exposed to someone with active TB disease, can I give TB to others?

ACTIVE TB DISEASE

How is active TB disease treated?

What are the side effects of TB medicines?

Why do I need to take TB medicines regularly?

What is directly observed therapy (DOT)?

How can I remember to take my TB medicines if I am not on DOT?

How can I keep from spreading TB?

What are multidrug-resistant TB and extensively drug-resistant TB?
iv | Q&A About TB
Q&A About TB | 1

INTRODUCTION

What is TB?

Tuberculosis (TB) is a disease caused by bacteria called Mycobacterium tuberculosis*. 

The bacteria usually attack the lungs. But, TB bacteria can attack any part of the body 

such as the kidney, spine, and brain. If not treated properly, TB disease can be fatal. 

TB disease was once the leading cause of death in the United States.

TB is spread through the air from one person to another. The bacteria are put into the air 

when a person with active TB disease of the lungs or throat coughs, sneezes, speaks, or 

sings. People nearby may breathe in these bacteria and become infected.

However, not everyone infected with TB bacteria becomes sick. People who are infected 

but not sick have what is called latent TB infection. People who have latent TB infection 

do not feel sick, do not have any symptoms, and cannot spread TB to others. But, some 

people with latent TB infection go on to get TB disease.

There is good news. People with active TB disease can be treated if they seek medical 

help. Even better, most people with latent TB infection can take medicine so that they 

will not develop active TB disease.

Why is TB still a problem in the United States?

In the early 1900s, TB killed one out of every seven people living in the United States 

and Europe. Starting in the 1940s, scientists discovered the first of several medicines 

now used to treat TB. As a result, TB slowly began to decrease in the United States. But 

in the 1970s and early 1980s, the country let its guard down and TB control efforts were 

neglected. This led to an increase in the number of TB cases between 1985 and 1992. 

However, with increased funding and attention to the TB problem, there has been a 

steady decline in the number of persons with TB since 1993. 

But TB continues to be a problem. For example, the number of TB cases is still declining, 

but the speed of decline has slowed since 2003. Multidrug-resistant TB (MDR TB) 

remains a concern, and extensively drug-resistant TB (XDR TB) has become an 

important issue. And, racial and ethnic minority populations and foreign-born individuals 

continue to account for a large number of TB cases in the United States.

This booklet answers common questions about TB. Please ask your doctor or nurse if you 

have other questions about latent TB infection or TB disease.

* Words that are underlined can be found in the glossary on page 16.
2 | Q&A About TB

How is TB spread?

TB is spread through the air from one person to another. The bacteria are put into the air 

when a person with active TB disease of the lungs or throat coughs, sneezes, speaks, or 

sings. People nearby may breathe in these bacteria and become infected.

When a person breathes in TB bacteria, 

the bacteria can settle in the lungs and 

begin to grow. From there, they can move 

through the blood to other parts of the 

body, such as the kidney, spine, and brain.

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 active TB disease are most likely to spread it to people they spend time with 

every day. This includes family members, friends, and coworkers or schoolmates.

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 bacteria to others 

• usually have a positive skin test reaction or positive TB blood test (see pages 5-6)

• may develop active TB disease if they do not receive treatment for latent TB infection 

(see page 7)

Many people who have latent TB infection never develop active 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, multiply, and cause TB disease. 
Q&A About TB | 3

What is active 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 active TB disease. The bacteria 

attack the body and destroy tissue. If this occurs in the lungs, the bacteria can actually 

create a hole in the lung. Some people develop active TB disease soon after becoming 

infected (within weeks) before their immune system can fight the TB bacteria.

Other people may get sick years later, when their immune system becomes weak 

for another 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 

• silicosis 

• cancer of the head or neck 

• leukemia or Hodgkin’s disease 

• severe kidney disease 

• low body weight 

• certain medical treatments (such as corticosteroid treatment or organ transplants) 

• specialized treatment for rheumatoid arthritis or Crohn’s disease 

Symptoms of TB depend on where in the body the TB bacteria are growing. TB in the 

lungs may cause symptoms such as

• a bad cough that lasts 3 weeks or longer 

• pain in the chest 

• coughing up blood or sputum (phlegm from deep inside the lungs) 

Other symptoms of active TB disease are

• weakness or fatigue 

• weight loss 

• no appetite 

• chills 

• fever 

• sweating at night 

For information on how active TB disease is treated, see page 10.
4 | Q&A About TB

The Difference Between Latent TB Infection and Active TB Disease

A PERSON WITH LATENT TB INFECTION

•	 Does not feel sick

•	 Has no symptoms

•	 Cannot spread TB bacteria to others

•	 Usually has a positive skin test or 	 	 	

positive TB blood test

•	 Has a normal chest x-ray and a negative 

sputum smear

•	 Should consider treatment for latent TB 	 	

infection to prevent active TB disease

A PERSON WITH ACTIVE TB DISEASE

•	 Usually feels sick

•	 Has symptoms that may include:

	 - a bad cough that lasts 3 weeks or longer

- pain in the chest 

- coughing up blood or sputum 

	 - weakness or fatigue

- weight loss 

- no appetite 

- chills 

- fever 

- sweating at night

•	 May spread TB bacteria to others

•	 Usually has a positive skin test or positive

TB blood test

•	 May have an abnormal chest x-ray, or positive

sputum smear or culture

•	 Needs treatment for active TB disease
Q&A About TB | 5

LATENT TB INFECTION

Should I get tested for TB?

You should get tested for TB if

• You have spent time with a person known or suspected to have active TB disease; or 

• You have HIV infection or another condition that weakens your immune system and 

puts you at high risk for active TB disease; or 

• You have symptoms of active TB disease; or

• You are from a country where active TB disease is very common (most countries in 

Latin America and the Caribbean, Africa, Asia, Eastern Europe, and Russia); or

• You live somewhere in the United States where active TB disease is more common 

such as a homeless shelter, migrant farm camp, prison or jail, and some nursing 

homes; or

• You inject illegal drugs.

What are the tests for TB infection?

The TB skin test

The TB skin test may be used to find out if you are infected with TB bacteria. You can 

get a skin test at the health department or at your doctor’s office. A health care worker 

will inject a small amount of testing fluid (called tuberculin or PPD) just under the skin 

on the lower part of your arm. After 2 or 3 days, you must return to have your skin test 

read by the health care worker. You may have swelling where the tuberculin was injected. 

The health care worker will measure this swelling and tell you if your reaction to the test 

is positive or negative. A positive reaction usually means that you have been infected by 

someone with active TB disease.
6 | Q&A About TB

If you have recently been infected with TB bacteria, your TB skin test reaction may not 

be positive yet. You may need a second skin test 8 to 10 weeks after the last time you 

spent time with the person with active TB disease. This is because it can take several 

weeks after infection for your immune system to react to the TB skin test. If your reaction 

to the second test is negative, you probably do not have TB infection.

Special TB blood tests

These are new tests available that use a blood sample to find out if you are infected with 

TB bacteria. The tests measure the response of TB proteins when they are mixed with a 

small amount of blood. Since they are relatively new, few health departments offer these 

blood tests. If your health department does offer the special TB blood tests, only one visit 

is required to draw blood for the test. Examples of these special TB blood tests include 

QuantiFERON®-TB Gold (QFT-G) and T-Spot®.TB test.

What if I have a positive test for TB infection?

If you have a positive reaction to the TB skin test, or special TB blood test, your doctor or 

nurse may do other tests to see if you have active TB disease. These tests usually include 

a chest x-ray. They may also include a test of the sputum you cough up. Because the TB 

bacteria may be found somewhere other than your lungs, your doctor or nurse may check 

your blood or urine, or do other tests. If you have active TB disease, you will need to take 

medicine to treat the disease (see page 10).

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 getting 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 due to infection with the TB bacteria. 

Your positive reaction is more likely to mean you have been infected with TB bacteria if

• You recently spent time with a person who has active TB disease; or 

• You are from an area of the world where active TB disease is very common (such as 

most countries in Latin America and the Caribbean, Africa, Asia, Eastern Europe, and 

Russia); or 

• You spend time where TB disease is common (homeless shelters, migrant farm 

camps, drug-treatment centers, health care clinics, jails, prisons). 

The special TB blood tests are not affected by prior BCG vaccination and are less likely 

to give a false-positive result.
Q&A About TB | 7

If I have latent TB infection, how can I keep from developing active TB disease?

Many people who have latent TB infection never develop active TB disease. But some people 

who have latent TB infection are more likely to develop active TB disease than others. Those at 

high risk for active TB disease include

• people with HIV infection 

• people who became infected with TB bacteria in the last 2 years 

• babies and young children 

• people who inject illegal drugs 

• people who are sick with other diseases that 

weaken the immune system (see page 3)

• elderly people 

• people who were not treated correctly for TB in the past 

If you have latent TB infection (a positive TB skin test reaction or positive TB blood test) 

and you are in one of these high-risk groups, you need to take medicine to keep from 

developing active TB disease. This is called treatment for latent TB infection. There are 

several treatment options. You and your health care provider must decide which treatment 

is best for you.

The medicine usually taken for the treatment of latent TB infection is called isoniazid 

(INH). Taken for 6 to 9 months, INH kills the TB bacteria that are in the body. If you take 

your medicine as instructed by your doctor or nurse, it can keep you from developing 

active TB disease. Children, adolescents, and HIV-infected persons with latent TB 

infection need to take INH for 9 months.

Because there are less bacteria, treatment for latent TB infection is much easier than 

treatment for TB disease. Usually, only one drug is needed to treat latent TB infection. 

A person with active TB disease has a large amount of TB bacteria in the body. Several 

drugs are needed to treat active TB disease.

Sometimes people are given treatment for latent TB infection even if their skin test 

reaction is negative. This is often done with infants, children, and HIV-infected persons 

who have recently spent time with someone with active TB disease. This is because they 

are at very high risk of developing active TB disease soon after they become infected 

with TB bacteria.
8 | Q&A About TB

It is important that you take all the pills as prescribed. If you start taking INH, you will 

need to see your doctor or nurse on a regular schedule. The doctor or nurse will check on 

how you are doing. Some people have serious side effects from INH. If you have any of 

the following side effects, call your doctor or nurse right away:

• no appetite 

• nausea 

• vomiting 

• yellowish skin or eyes 

• fever for 3 or more days 

• abdominal pain 

• tingling in the fingers and toes 

WARNING: Frequent or heavy drinking of alcoholic beverages (wine, beer, and liquor)

	 while taking INH can be dangerous. Check with your doctor or nurse for more information.

People who have latent TB infection need to know the symptoms of active TB disease 

(see page 3). If they develop symptoms of active TB disease, they should see a doctor 

right away.

What if I have HIV infection?

Because HIV infection weakens the immune system, people with latent TB infection and 

HIV infection are at very high risk of developing active TB disease. All persons with HIV 

infection should be tested to find out if they have latent TB infection. If they have latent TB 

infection, they need treatment as soon as possible to prevent them from developing active 

TB disease. If they have active TB disease, they must take medicine to treat the disease.

NOTE: Active TB disease can be prevented and treated, even in people with HIV infection.
Q&A About TB | 9

If I was exposed to someone with active TB disease, can I give TB to others?

If you were exposed to someone with active TB disease, you may become infected with 

TB bacteria, but you would not be able to spread the bacteria to others right away. Only 

persons with active TB disease can spread TB to others. Before you would be able to 

spread TB bacteria to others, you would have to breathe in TB bacteria and become 

infected. Then the active bacteria would have to multiply in your body and cause active 

TB disease. At this point, you could possibly spread TB bacteria to others. 

Some people develop active TB disease soon (within weeks) after becoming infected, 

before their immune system can fight the TB bacteria. Other people may get sick years 

later, when their immune system becomes weak for another reason. Many people with TB 

infection never develop TB disease. 

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 cannot spread TB bacteria to others. People who have latent TB 

infection can be treated to prevent developing active TB disease. 
10 | Q&A About TB

ACTIVE TB DISEASE

How is active TB disease treated?

There is good news for people with active TB disease! It can almost always be treated and 

cured with medicine. But the medicine must be taken as directed by your doctor or nurse.

If you have active TB disease, you will need to take several different medicines. This is 

because there are many bacteria to be killed. Taking several medicines will do a better job 

of killing all of the bacteria and preventing them from becoming resistant to the medicines.

The most common medicines used to treat TB are

• isoniazid (INH) 

• rifampin (RIF)

• ethambutol 

• pyrazinamide 

If you have active TB disease 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 or visit with 

friends.

Having active TB disease 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 

active TB disease. The medicines that you are taking should not affect your strength, 

sexual function, or ability to work. If you take your medicines as directed by your doctor 

or nurse, they should kill all the TB bacteria. This will keep you from becoming sick again.
Q&A About TB | 11

What are the side effects of TB medicines?

If you are taking medicines for TB, you should take it as directed by your doctor or nurse. 

The medicines may cause side effects. Some side effects are minor problems. Others are 

more serious. If you have a serious side effect, call your doctor or nurse immediately.

You may be told to stop taking your medicine or to return to the clinic for tests.

The side effects listed below are serious. If you have any of these symptoms, call your 

doctor or nurse immediately:

• no appetite 

• nausea 

• vomiting 

• yellowish skin or eyes 

• fever for 3 or more days 

• abdominal pain 

• tingling fingers or toes 

• skin rash 

• easy bleeding 

• aching joints 

• dizziness 

• tingling or numbness around the mouth 

• easy bruising 

• blurred or changed vision 

• ringing in the ears 

• hearing loss 

The side effects listed below are minor problems. If you have any of these side effects, 

you can continue taking your medicine.

• Rifampin can turn urine, saliva, or tears orange. The doctor or nurse may advise you 

not to wear soft contact lenses because they may get stained. 

• Rifampin can make you more sensitive to the sun. This means you should use a good 

sunscreen and cover exposed areas so you don’t burn. 

• Rifampin makes birth control pills and implants less effective. Women who take 

rifampin should use another form of birth control. 

• If you are taking rifampin as well as methadone (used to treat drug addiction), you 

may have withdrawal symptoms. Your doctor or nurse may need to adjust your 

methadone dosage. 
12 | Q&A About TB

Why do I need to take TB medicines regularly?

TB bacteria die very slowly. It takes at least 6 months for the medicines 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 

medicines until all the TB bacteria are dead, even though you may feel better and have no 

more symptoms of active TB disease.

If you don’t continue taking your medicines or you aren’t taking all your medicines 

regularly, this can be very dangerous. The TB bacteria will grow and you will remain sick 

for a longer time. The bacteria may also become resistant to the medicines you are taking. 

You may need new, different medicines to kill the TB bacteria if the old medicines no 

longer work. These new medicines 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 medicines as 

directed by your doctor or nurse.

What is directly observed therapy (DOT)?

The best way to remember to take your medicines is to get directly observed therapy 

(DOT). 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 medicines at this 

place while the health care worker watches.

DOT helps in several ways. The health care worker can help you remember to take your 

medicines and complete your treatment. This means you will get well as soon as possible. 

With DOT, you may need to take medicines only 2 or 3 times each week instead of every day. 

The health care worker will make sure that 

the medicines are working as they should. 

This person will also watch for side effects 

and answer questions you have about TB.

Even if you are not getting DOT, you must 

be checked at different times to make sure 

everything is going well. You should see 

your doctor or nurse regularly while you 

are taking your medicines. This will 

continue until you are cured.
Q&A About TB | 13

How can I remember to take my medicines if I am not on DOT?

The only way to get well is to take your medicines exactly as directed by your doctor or 

nurse. This may not be easy! You will be taking your medicines for a long time (6 months 

or longer), so you should get into a routine. Here are some ways to help you remember to 

take your medicines:

• Take your pills at the same time every day — for example, you can take them before 

eating breakfast, during a coffee break, or after brushing your teeth.

• Ask a family member or a friend to remind you to take your pills. 

• Mark off each day on a calendar as you take your medicine. 

• Put your pills in a weekly pill dispenser. Keep it by your bed or in your 

purse or pocket. 

	 NOTE: Remember to keep all medicine out of reach of children.

If you forget to take your pills one day, skip that dose and take the next scheduled dose. 

Tell your doctor or nurse that you missed a dose. You may also call your doctor or nurse 

for instructions.

How can I keep from spreading TB?

The most important way to keep from 

spreading TB is to take all your medicines, 

exactly as directed by your doctor or nurse. 

You also need to 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 medicines are 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 active TB disease to go to a hospital, you may be put in a 

special room. These rooms use air vents that keep TB bacteria from spreading to other 

rooms. People who work in these special 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 for anything you need that is not in your room.
14 | Q&A About TB

If you are infectious while you are at home, there are things you can do to protect 

yourself and others near you. 

• Take your medicines as directed. This is very important! 

• Always cover your mouth with a tissue when you cough, sneeze, or laugh. Put the 

tissue in a closed bag 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 will 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 the medicines for about 2 or 3 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, including returning to work or school. Remember, you will get well only if 

you take your medicines exactly as directed by your doctor or nurse.

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 TB 

infection. TB is especially dangerous for children and HIV-infected persons. If infected 

with TB bacteria, these people need medicine right away to keep from developing active 

TB disease.
Q&A About TB | 15

What are multidrug-resistant TB (MDR TB) and extensively drug-resistant TB (XDR TB)?

Sometimes the TB bacteria are resistant to the medicines used to treat TB disease. This 

means that the medicine can no longer kill the bacteria. Multidrug-resistant TB, or MDR 

TB, is caused by bacteria that are resistant to two or more of the most important TB 

medicines: INH and RIF. 

A more serious form of MDR TB is called extensively drug-resistant TB (XDR TB). 

XDR TB is a rare type of TB that is resistant to nearly all medicines used to treat TB 

disease. 

If you do not take your medicines as directed by your doctor or nurse, the TB bacteria 

may become resistant to a certain medicine. Also, people who have spent time with 

someone sick with MDR TB or XDR TB disease can become infected with these 

multidrug-resistant bacteria. 

Drug resistance is more common in people who

• have spent time with someone with drug-resistant TB disease 

• do not take all of their medicines as directed by their doctor or nurse 

• develop active TB disease again, after having taken TB medicines in the past 

• come from areas where drug-resistant TB is common 

People with MDR TB or XDR TB disease must be treated with special medicines. These 

medicines are not as good as the usual medicines for TB, and they may cause more side 

effects. Also, people with MDR TB and XDR TB disease must see a TB expert who can 

closely observe their treatment to make sure it is working. Treatment takes much longer 

than regular TB. And, people with both MDR TB and XDR TB are at greater risk of 

dying from the disease. 
16 | Q&A About TB

GLOSSARY OF TERMS RELATED TO TB

Active TB disease – an illness in which TB bacteria are multiplying and attacking a part 

of the body, usually the lungs. The symptoms of active TB disease include weakness, 

weight loss, fever, no appetite, chills, and sweating at night. Other symptoms of active 

TB disease depend on where in the body the bacteria are growing. If active TB disease is 

in the lungs (pulmonary TB), the symptoms may include a bad cough, pain in the chest, 

and coughing up blood. A person with active TB disease may be infectious and spread TB 

bacteria to others.

BCG – a vaccine for TB named after the French scientists who developed it, Calmette and 

Guérin. BCG is rarely used in the United States, but it is often given to infants and small 

children in other countries where TB is common.

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 the chest. A doctor can look at this film to see whether TB 

bacteria have damaged the 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 medicines 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 medicines while the health 

care worker watches.

Extensively drug-resistant TB (XDR TB) - XDR TB is a rare type of TB disease that is 

resistant to nearly all medicines used to treat TB.

Extrapulmonary TB – active TB disease in any part of the body other than the lungs 

(for example, the kidney, spine, brain, 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 active TB disease.
Q&A About TB | 17

INH or isoniazid – a medicine used to prevent active TB disease in people who have latent 

TB infection. INH is also one of the four medicines often used to treat active TB disease. 

It is considered a first-line drug.

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 

bacteria to others, and usually have a positive TB test. But they may develop active TB 

disease if they do not receive treatment for latent TB infection.

Multidrug-resistant TB (MDR TB) – active TB disease caused by bacteria resistant to two of 

the most important medicines: INH and RIF.

Mycobacterium tuberculosis – bacteria that cause latent TB infection and active TB disease.

Negative – usually refers to a test result. If you have a negative TB skin test reaction, you 

probably do not have TB infection.

Positive – usually refers to a test result. If you have a positive TB skin test reaction, you 

probably have TB infection.

Pulmonary TB – active TB disease that occurs in the lungs, usually producing a cough that 

lasts 3 weeks or longer. Most active TB disease is pulmonary.

Resistant bacteria – bacteria that can no longer be killed by a certain medicine.

Rifampin (RIF) – one of the four medicines often used to treat active TB disease. It is 

considered a first-line drug. 

Smear – a test to see whether there are TB bacteria in your phlegm (sputum). To do this 

test, lab workers smear the sputum 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 to get the results.
18 | Q&A About TB

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 skin test – a test that is often used to find out if you are infected with TB bacteria. 

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 TB infection. Other tests will be 

needed to find out if you have latent TB infection or TB disease.

TB blood test – a new test that uses a blood sample to find out if you are infected with TB 

bacteria. The test measures the response to TB proteins when they are mixed with a small 

amount of blood. Examples of these special TB blood tests include QuantiFERON®-TB 

Gold (QFT-G) and T-Spot®.TB test.

Tuberculin or PPD – a liquid that is injected under the skin on the lower part of your 

arm during a TB skin test. If you have TB infection, you will probably have a positive 

reaction to the tuberculin.

For more information 

or to order educational materials about TB, 

contact your local Health Department

Or visit:

CDC Division of Tuberculosis Elimination Website

www.cdc.gov/tb

CS123759