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The Epidemiology of Tuberculosis
Lex Gibson, Virginia TB Program
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TB Infection VS TB Disease
Infection Disease
TB Bacilli in Body Yes YesPPD Usually Pos. Usually Pos.CXR Usually Normal Usually Abn.Sputum Smears/Cult Neg. Usually Pos.Symptoms None Cough, Fever, Wt. Loss Infected Yes YesInfectious No Often, before treatment A “Case” of TB No Yes
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What is a PPD?
• Intradermal test of .1ml(5TU) of purified protein derivative.
• Measures TB infection
• False positives(cross reactions, non-specific in low risk populations)
• False negatives(technique, storage)
• Read in MM of induration
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Reading the Mantoux Test
• Read in 48-72 hours
• Measure only raised area, not redness
• Measure across the widest area
• The diameter of the raised area should be measured
• Measure and report results in millimeters
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Interpreting the results
5mm is positive for those:
– known to have or suspected of having HIV infection
– close contacts of a person with infectious TB
– with a chest x-ray suggestive of previous TB
– who inject drugs(if HIV status unknown)
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10 mm is positive for those:– with certain medical conditions, excluding HIV
infection– who inject drugs(if HIV negative)– foreign born persons from areas where TB is
common– medically underserved, low income pop-
ulations, including high-risk racial and ethnic groups
– Residents of long term care facilities– Children younger than 4 years of age– Locally identified high risk groups
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Determining Infectiousness
• Smear Results
• CXR Findings
• Symptoms
• Smear Results
• CXR Findings
• Symptoms
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Increased Risk of Transmission
• Infectiousness of Source
• Duration of Exposure
• Environment
• Susceptibility of Contact
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Contact Investigation
• Screening individuals who have shared the same air as an infectious case of TB
• Investigations are done systematically
• Significant reactors receive a cxr and are evaluated for Treatment of disease or preventive therapy
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Concentric Circle
close
Casual/Work
Community
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Scenario 1
• Twenty-eight year old school teacher has a positive PPD during a routine screening. No risk factors for TB. What do you do?
• CXR shows pleural effusions. What's next?• Obtain sputum, pleural specimen, and possibly
start on multiple anti-TB drugs. Sputum's are negative but pleural specimen is sm. Pos.
• Now what do you do?
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• Contact investigation- All family members have negative PPD’s and are asymptomatic, is further testing necessary?
• Normally not……unfortunately, word spread through the community that an elementary school teacher has TB. The media, parents and school system are demanding that PPD’s be done on everyone. What do you do?
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• Educate media, parents and school system
• Your initial compromise is to skin test just one classroom rather than the entire school, but your health department receives 45% of its funding from the locality. The city council/board of supervisors wants to know why you are refusing to protect their school children from getting TB. What do you do?
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• If political pressure prevails and the entire school is tested, what might be some of the consequences?
• This is a low risk population group, greater than 50% of the positive PPD’s identified will be false positives. Preventive treatment with INH exposes the individual to possible liver damage from the INH
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Scenario 2
A sputum smear, culture positive Mtb case is diagnosed in a large open factory that manufactures circuit boards. Air is recirculated within the facility. Three other cases have been diagnosed in the facility during the past three years. Over 90% of the employees are from the Philippines and previous contact investigations have demonstrated a 70-80% reactor rate. Less than 7% of past positives have completed an adequate course of treatment for latent TB infection. All close family contacts are previous positive reactors. How do you proceed with the investigation?
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• Who would you screen and what tools would you use?
• PPD past negatives in the immediate vicinity of the case, factory wide symptom assessment of past positives, and collect sputums on those with signs and symptoms
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TB Advances Over Time
400 B.C. Syndrome Described
1882 Bacteria Identified
1895 X-Ray Invented
1934 PPD Available
1950 Effective Therapy
1990 DOT
FUTURE ??
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Funding Trends
$1,700,000
$1,800,000
$1,900,000
$2,000,000
$2,100,000
1996 1997 1998 1999 2000
Not adjusted for inflation nor salary increases
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Global Tuberculosis
• 8-10 Million new cases/year
• 2-3 million deaths/year
• Tuberculosis is the 2nd leading cause of deaths by infectious diseases
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Tuberculosis in the U.S.
• 15 million infected
• 17,000 + new cases per year
• TB cases decreased steadily until 1985, then increased and has now begun to decrease again
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TB Case Rates US &Virginia
1987-1999
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
US
Virginia
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Epidemiology of TuberculosisVirginia-1999
• 334 Cases of TB in 1999
• 4.9/100,000
• 5000+ people starting INH
• 77,000+ skin-tests given
• 4,000+ contacts identified
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Pitt/DanW. PiedmontSouthsideT. JeffersonRapp/RapidanNumber of TB Cases No Cases 1 - 5 6 - 15 16 - 30 > 30 Miles40200Virginia Tuberculosis Morbidity # CasesDistricts 199977 cases
Rate/100,000
< 3 per 100,000
3.1- 5 per 100,000
5.1 - 10 per 100,000
>10 per 100,000
Miles
40200
Virginia Tuberculosis Morbidity Rate/100,000Districts 1999
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Pitt/Dan
W. Piedmont
T. Jefferson
Rapp/Rapidan
Number of TB Cases No Cases
1 - 5
6 - 15
16 - 30
> 30
Miles
40200
Virginia Tuberculosis Morbidity # Cases
Districts 1999
77 cases
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Case rates for selected groupsIn Virginia(1996)
• Homeless- 411.3 /100,000 • Vietnamese- 159.5 /100,000• Guatemalan- 108.3 /100,000• Korean- 63 /100,000• Philippines-59.9 /100,000• Foreign born- 49.7 /100,000• Nursing & Adult Homes- 39.7 /100,000
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Case Rates for selected groups
• Chinese- 37.7 /100,000 • Corrections- 8.9 /100,000• Hispanic- 26.8 /100,000 • >65 years - 17.3 /100,000• U.S. born minorities- 8.1 /100,000• U.S. born whites- 2.1 /100,000
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0 10 20 30 40 50 60 70 80
U.S. Born Minorities
Foreign Born
Elderly(>64)
Hispanic
Asian/Pacific Isl.
Homeless
Corrections
Nursing/Adult Home
3.8
15
4.1
5.3
13.1
73.4
1.7
7.8
Relative Risk of TB DiseaseSelected Populations
Populations bases on 1990 Census Data
1996
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Percent of Total TB by RaceVirginia -1992-1999
5
10
15
20
25
30
35
40
45
1992 1993 1994 1995 1996 1997 1998 1999
Hispanic
Asian
Black
White
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US & Foreign-Born TB CasesVirginia 1992-1999
2530354045505560657075
1992 1993 1994 1995 1996 1997 1998 1999
Foreign
US Born
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% of Total TB By Age GroupVirginia 1992-1999
0
5
10
15
20
25
30
35
40
1992 1993 1994 1995 1996 1997 1998 1999
0-14yrs
15-24yrs
25-44yrs
45-64yrs
65+yrs
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% Foreign-Born By Age GroupVirginia 1992-1999
0
10
20
30
40
50
60
1992 1993 1994 1995 1996 1997 1998 1999
0-14yrs
15-24yrs
25-44yrs
45-64yrs
65+yrs
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% US Whites By Age GroupVirginia 1992-1999
0
10
20
30
40
50
60
70
1992 1993 1994 1995 1996 1997 1998 1999
0-14yrs
15-24yrs
25-44yrs
45-64yrs
65+yrs
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% US Blacks By Age GroupVirginia 1992-1999
0
5
10
15
20
25
30
35
40
1992 1993 1994 1995 1996 1997 1998 1999
0-14yrs
15-24yrs
25-44yrs
45-64yrs
65+yrs
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% Foreign-Born By RaceVirginia 1992-1999
0
10
20
30
40
50
60
70
80
1992 1993 1994 1995 1996 1997 1998 1999
Hispanic
Asian
Black
White
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% Foreign-born CasesBy Region*
0 10 20 30 40 50
Europe
E. Med.
SE Asia
Africa
Americas
W. Pacific
19991990
*Based on WHO regions
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Foreign-Born TB Cases Arrival to Onset of Disease
1995 - 1997
• Less than 1 year 36.1%
• From 1 to 2 years 11.1%
• From 3 to 5 years 15.3%
• Over 5 years 31.5%
• Unknown 6.0%
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Tuberculosis by Agegroup and Foreign-born1999
65+26%
25-4434%
15-2412%
0-43% 5-14
1%
45-6424%
FOREIGN-BORN48%
US-BORN52%
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TB/HIV-1999
• 324 TB Cases Reported Prior to Death
• 231 (72%) were offered HIV testing
• 197(85%) were tested
• 16 (8%) were Positive0
2
4
6
8
10
12
15-24 25-44 45-64 65+
Agegroup
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% TB Cases Tested withDrug Resistance 1993-1999
6
8
10
12
14
16
18
1993 1994 1995 1996 1997 1998 1999
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% Drug Resistant Foreign-Born & US Born
1993-1999
0
10
20
30
40
50
60
70
80
90
1993 1994 1995 1996 1997 1998 1999
US Born
Foreign
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DOT The standard of treatmentThe standard of treatment Where one observes client taking medsWhere one observes client taking meds 216 patients on DOT in 1999216 patients on DOT in 1999 66.6 % of cases on DOT in 199966.6 % of cases on DOT in 1999
0
15
30
45
60
75
1992 1993 1994 1995 1996 1997 1998 1999
Percent
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% TB Cases with Social Problems that Impact Treatment
1993-1999
0
5
10
15
20
25
1993 1994 1995 1996 1997 1998 1999
Unemploy Homeless Etoh/Drug
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Quarantine/Legal Isolation
• Intervention of last Resort
• Difficult to Accomplish(weak laws, human rights issues)
• Limited options for isolation (Corrections)
• Have other interventions been exhausted?