The Epidemiology of Tuberculosis

The Epidemiology of Tuberculosis

Lex Gibson, Virginia TB Program

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

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

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

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)

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

Determining Infectiousness

• Smear Results

• CXR Findings

• Symptoms

• Smear Results

• CXR Findings

• Symptoms

Increased Risk of Transmission

• Infectiousness of Source

• Duration of Exposure

• Environment

• Susceptibility of Contact

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

Concentric Circle

close

Casual/Work

Community

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?

• 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?

• 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?

• 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

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?

• 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

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 ??

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

Global Tuberculosis

• 8-10 Million new cases/year

• 2-3 million deaths/year

• Tuberculosis is the 2nd leading cause of deaths by infectious diseases

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

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

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

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

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

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

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

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

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

US & Foreign-Born TB CasesVirginia 1992-1999

2530354045505560657075

1992 1993 1994 1995 1996 1997 1998 1999

Foreign

US Born

% 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

% 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

% 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

% 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

% 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

% Foreign-born CasesBy Region*

0 10 20 30 40 50

Europe

E. Med.

SE Asia

Africa

Americas

W. Pacific

19991990

*Based on WHO regions

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%

Tuberculosis by Agegroup and Foreign-born1999

65+26%

25-4434%

15-2412%

0-43% 5-14

1%

45-6424%

FOREIGN-BORN48%

US-BORN52%

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

% TB Cases Tested withDrug Resistance 1993-1999

6

8

10

12

14

16

18

1993 1994 1995 1996 1997 1998 1999

% 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

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

% 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

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?