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Disease Awareness
December 2015 • Facts
Tuberculosis
Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis. It occurs
most often in people with weakened immune systems and in people who
weren’t born in the United States. It primarily affects the lungs, in which case
it’s usually infectious. But it can also affect other parts of the body such as the
brain, kidneys, or spine. In these cases it’s usually not infectious. Not everyone
infected with TB bacteria gets sick. There are two types of TB infection: latent
TB infection and TB disease.
Latent Tuberculosis Infection
In the first weeks or months after exposure, most people mount an immune
response that keeps the bacteria under control. Immune cells form a barrier
around the bacteria. Live bacteria are present, but they are contained. This
results in latent TB infection. People with latent TB infection:
• Don’t have symptoms
• Aren’t contagious
• Usually test positive with a TB skin test or blood test
• Usually have a normal chest x-ray and negative sputum smear or culture
• Can be treated to prevent them from developing active disease
Tuberculosis Disease
TB bacteria are active in TB disease. They grow and attack the body and
make the person sick. Active TB bacteria in the lungs can be passed to others.
Bacteria can enter the air when an infected person coughs or sneezes and
infect other people.
Tuberculosis Facts
In the United States:
• M
ore than 11 million people have
latent TB infection.1
• 9
,421 TB cases were reported in
2014. 2
• 555 TB deaths occurred in 2013. 2
• 2
out of every 3 TB cases occur in
foreign-born people. 2
TB case rates are2:
• 2
9 times higher for Asians than for
whites.
• 8
times higher for both African
Americans and Hispanics than for
whites.
Tuberculosis
and National Origin
• Loss of appetite
The country a person was born in has
a lot to do with their risk for having
TB disease. People who live in the
United States but who weren’t born
here have a much higher incidence of
TB. In fact, it’s about 13 times higher.3
The majority of people in this group
who have TB disease were born in 5
countries. These are4:
• Chills or fever
• Mexico
• Night sweats
• The Philippines
Symptoms of Tuberculosis Disease
Most people with TB disease have 1 or more of these general symptoms:
• Feeling weak or tired
• Weight loss
• India
• Vietnam
• China
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Tuberculosis
Facts
Symptoms of TB disease in the lungs include:
• Coughing for 3 weeks or longer
• Chest pain
• Coughing up blood
Sometimes TB affects other parts of the body. In these cases, the
symptoms depend on where the infection is.
Risk for Tuberculosis Disease
Many people with latent TB infection never develop TB disease. But some
people aren’t able to fight the TB bacteria. The bacteria become active
and cause TB disease. People have a higher chance of getting TB disease
if they5:
• Have HIV infection
• Were infected with TB bacteria in the last 2 years
• Are a child younger than 5 years of age
• Are elderly
• Take some types of medicines
• H
ave other health problems that make it hard for the body to fight
disease (eg, diabetes and certain types of cancer)
• Are underweight
• Smoke cigarettes
• Abuse alcohol and/or drugs
People Who Should Get Tested
Tuberculosis
and HIV Coinfection
HIV infection is the greatest risk
factor for progression of latent TB
infection to TB disease.
• I n people with latent TB infection
and untreated HIV, the risk of
developing TB disease is 7% to
10% each year.7
• I n people with latent TB infection
and a healthy immune system, the
risk of developing TB disease is
10% over their lifetime.7
Tuberculosis and BCG
Vaccination
Bacille Calmette-Guerin (BCG) is a TB
vaccine. It:
• I s used in many countries where
TB is common
• Isn’t used in the United States
• D
oesn’t always prevent people
from getting TB
• M
ay cause a false-positive TB skin
test but will not affect a TB blood
test
Not everyone should be tested for TB. Testing is appropriate for people
who are at increased risk of infection or progression to active disease. In
addition to the people listed above, this includes people who5,6:
• Have had close contact with someone who has TB disease
• Have symptoms of TB disease
• Are from a country where TB disease is very commona
• L ive or work where TB disease is more common (eg, homeless shelter,
jail, nursing home)
• A
re in healthcare and work closely with those who are at increased risk
of TB disease
• A
re infants, children, or adolescents exposed to adults who are at
increased risk of TB.
Includes most countries in Latin America, the Caribbean, Africa, Asia, Eastern Europe,
and Russia.
a
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Tuberculosis
Facts
Tuberculosis Testing
References
There is no gold standard test for TB. Two tests in common use are:
1.
• TB skin test
• Interferon-gamma release assay (IGRA) blood test
In the TB skin test, a small amount of test fluid is injected into the skin on
the lower part of the arm. A return visit to a trained healthcare worker 2
to 3 days later is needed. He/she will ‘read’ the test by looking for a small
bump on the arm. It’s a sign of a positive reaction.
An IGRA test uses a blood sample. It measures the immune system’s
reaction to TB bacteria. No return visit is needed.
Both tests can detect latent TB infection and TB disease. A positive result
means TB bacteria may be present. Further testing is needed to know for
sure. A negative result means that TB bacteria are probably not present.
But some people with TB might have a negative result. This is true with
either test. Neither test can be used to:
• Tell the difference between latent TB infection and TB disease
• Tell if a person will develop TB disease
IGRAs are preferred for people who6:
• H
ave received the bacille Calmette-Guerin (BCG) vaccination (see
sidebar on page 2)
• C
an’t or aren’t likely to return 2 to 3 days later to have a skin test read
by a trained healthcare worker
The skin test is preferred for testing children younger than 5 years of age.
enters for Disease Control and
C
Prevention. New, simpler way to treat
latent TB infection. cdc.gov/Features/
TuberculosisTreatment/. Updated
December 12, 2011. Reviewed August 13,
2014. Accessed October 20, 2015.
2. C
enters for Disease Control and
Prevention. Take on tuberculosis. cdc.gov/
tb/publications/infographic/default.htm.
Updated September 28, 2015. Accessed
October 20, 2015.
3. C
enters for Disease Control and
Prevention. Fact Sheet. Trends in
tuberculosis, 2014. cdc.gov/tb/
publications/factsheets/statistics/
tbtrends.htm. Accessed October 20, 2015.
4. C
enter for Strategic and International
Studies. Tackling tuberculosis abroad.
csis.org/files/publication/140604_
Moore_TacklingTBAbroad_Web.pdf.
Published June 2014. Accessed
October 20, 2015.
5. M
orbidity and Mortality Weekly Report.
Updated guidelines for using interferon
gamma release assays to detect
Mycobacterium tuberculosis infection—
United States, 2010. cdc.gov/mmwr/
PDF/rr/rr5905.pdf. Published June 2010.
Accessed October 20, 2015.
6. C
enters for Disease Control and
Prevention. Testing for tuberculosis (TB).
cdc.gov/tb/publications/factsheets/
testing/tb_testing.htm. Updated
December 19, 2014. Accessed
October 20, 2015.
7. C
enters for Disease Control and
Prevention. Core curriculum on
tuberculosis: what the clinician should
know. Chapter 2. Transmission and
pathogenesis of tuberculosis. cdc.gov/
tb/education/corecurr/pdf/chapter2.pdf.
Updated June 21, 2013. Accessed
October 20, 2015.
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