Communicable Disease Report 2002 - Focus on Tuberculosis ...

3The Regional Municipality of Peel

History of Tuberculosis

Tuberculosis (TB) has had a long and important role in human history.

Over the years, it has gone by many names, including “consumption”,

“white plague” and “phthisis”.1 Evidence from ancient Egyptian mummies

suggests TB has been with us for more than 4,000 years.1 In ancient Greece,

Hippocrates wrote of a common and deadly illness he called phthisis.1 In

Europe in the late 17th-century, one in every four deaths was attributable to

TB.1 During the first half of the 20th-century, TB remained the number one

killer of Canadians. Until the advent of modern antibiotics, TB was usually

treated in special isolation hospitals called sanitaria. In 1953, Canada reached

a peak of 19,000 sanitarium beds dedicated to the treatment of TB patients.

On average, TB patients stayed in sanitaria for just over one year, but many

stayed at the “san” for three to five years.1

Today, modern antibiotics are highly effective against tuberculosis (TB).

Most TB patients can recover at home and return to work within a few

weeks of onset. Most people do not require a hospital stay. In addition, the

usual duration of therapy has shortened to between six and nine months. As

a result of these and other developments, infectious diseases (of which TB is

only a small part) now account for less than 1% of all deaths in Canada.

Canada currently has one of the lowest incidences of TB in the world.

Tuberculosis

HIGHLIGHTS

• In 1998, the age-standardized incidence of tuberculosis (TB) per 100,000 population was higher in Peel (9.6) than Ontario (6.5) and Canada (5.9).

• In Peel between 1982 and 2001, the number of cases of TB almost doubled (48 to 90 cases), largely due to population growth.

• In Peel from 1992 to 2001, the highest incidence of TB was found in those over 60 years of age. The incidence of TB in men and women in Peel was similar over this same period.

• In Peel from 1992 to 2001, most cases of TB were in foreign-born individuals (range 89 to 97%). The majority of these cases were from three TB-endemic countries: India (31%), the Philippines (14%) and Vietnam (13%).

• The lungs were the predominant site affected by TB in individuals in both Peel and Ontario.

• In Peel from 1992 to 2001, 10% of TB cases were resistant to drugs.

—73% were resistant to isoniazid alone or in combination with another drug— 7% were multi-drug resistant (resistant to at least isoniazid and rifampin)

• The proportion of drug resistant TB cases in Peel was higher among foreign-born individuals than in those born in Canada.

4 Communicable Disease Report—2002

Unfortunately, the situation is not the same in other parts of the world.

One-third of the world’s population is infected with tuberculosis (TB).

Although effective treatment and prevention strategies exist, TB still kills two

to three million people every year (one death every 12 to 15 seconds), more

than either AIDS or malaria.

Biology of Tuberculosis

Tuberculosis (TB) is a disease caused by a bacterium called Mycobacterium

tuberculosis. TB mainly affects the lungs but can affect any other parts of

the body.2

Tuberculosis (TB) organisms are released into the air when someone with

infectious, active TB in their lungs or larynx coughs. TB spreads when these

organisms are inhaled. TB found in other parts of the body cannot be spread

to other people.

Frequent, repeated exposure to an infectious individual is usually required

before someone becomes infected with tuberculosis (TB). It is estimated

that exposure for several hours a day for a few months is necessary for an

average, healthy adult to acquire the infection. In some special circumstances,

the infection may be transmitted more readily.3

The vast majority of people with tuberculosis (TB) bacteria in their bodies

do not have an active infection—they remain well and cannot spread the

infection to others. The lifetime risk of inactive infection progressing to

active disease is 10%.3 Active disease occurs when the bacteria spread and

cause damage to the lungs and other parts of the body. Nearly all of the

statistics in this section refer to people with active TB.

High-risk groups for tuberculosis (TB) infection include all individuals who

have spent extended periods of time in parts of the world where the disease

is prevalent, Aboriginal people, people with HIV/AIDS, seniors and homeless,

urban-core residents.4 People living in overcrowded and sub-standard living

conditions are also at greater risk of developing a TB infection.4

People working in health care institutions, social service organizations and

correctional facilities may have frequent contact with high-risk individuals.

Effective occupational health programs can prevent the development of

tuberculosis in any exposed worker.4

Most people do not have frequent contact with, or are not among, the

high-risk groups listed and therefore are unlikely to become infected with

tuberculosis (TB).3


Incidence of Tuberculosis in Canada and Ontario

In 1998, Canada had one of the lowest active tuberculosis (TB) disease rates

in the world (about 5.9 cases per 100,000 population).5 Comparable figures

for Ontario and Peel for the same year were 6.5 and 9.6 cases per 100,000,

respectively.

In Canada in 1997, there were seven cases of tuberculosis (TB) per 100,000.6

This incidence was similar to the United States (seven cases per 100,000)6

and Australia (eight cases per 100,000)5, but significantly lower than TB-

endemic countries such as the Philippines (314 cases per 100,000),7 Vietnam

(189 cases per 100,000)7, India (187 cases per 100,000)7 and Pakistan (181

cases per 100,000).7

The number of tuberculosis (TB) cases reported in Ontario and Canada

has declined significantly since the Second World War.3,4 The sharp drop

between 1946 and 1947 was due to the introduction of the first antibiotics

effective against TB. In Ontario, the total number of TB cases peaked in

1943 (2,789 cases) (see Figure 1.1). By 1988, the number of cases declined to

a low of 644 cases. Since then, rates of TB in Ontario have stabilized, with an

average of about 790 cases each year. In 1999, 700 cases of TB were reported,

down from 779 cases in 1997.

Figure 1.1: Number of Reported Active Tuberculosis Cases by Year, Ontario, 1920–1999

Sources: Ontario data 1920–1990 from Public Health Branch, Ontario Ministry of Health and Long-Term Care. Ontario data 1991–1999 from RDIS, Ontario Ministry of Health and Long-Term Care, as of 07/17/2001.

0

500

1,000

1,500

2,000

2,500

3,000

1920

1926

1932

1938

1944

1950

1956

1962

1968

1974

1980

1986

1992

1998

Number of cases

Year

In Peel between 1992 and 2001, the incidence of tuberculosis (TB) fluctuated

between 7.5 and 13.3 cases per 100,000 population (see Figure 1.3 on the

following page). The incidence of TB in Ontario was generally lower than that

in Peel and has demonstrated a gradual decline since 1994 (see Figure 1.3 on

the following page).


Active Tuberculosis in Peel

Peel tuberculosis (TB) data are available for the last twenty years. Like

Ontario, the incidence of TB in Peel declined in the early 1980s, reaching a

low of five cases per 100,000 population in 1986 (see Figure 1.2). Incidence

increased from 1986 to 1990 and has since stabilized to between six and

11 cases per 100,000. The total number of cases of TB in Peel more than

doubled from 1982 to 2001 (48 to 90 cases), but this is largely due to

population growth.

Figure 1.2: Incidence of Active Tuberculosis by Year, Region of Peel, 1982–2001

*Crude rates per 100,000.

Sources: Peel data 1982–1989 from Public Health Branch, Ontario Ministry of Health and Long-Term Care. Peel data 1990–2001 from RDIS, Region of Peel Health Department, as of 07/22/2002. Statistics Canada, Population Estimates and Projections distributed by the Ontario Ministry of Health and Long-Term Care.

TB Rate

TB Cases

0

120

0

12

10

8

6

4

2

100

80

60

40

20

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

Number of cases Cases per 100,000*

Year


1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

11.6 11.3 13.3 8.2 10.3 10.8 9.6 7.5 11.3 9.6

0

15

12

9

6

3

7.8 7.5 8.0 7.3 7.1 6.9 6.5 6.1 NA NA

81 81 94 65 84 89 78 67 103 90

Peel

Ontario

Peel Cases

Cases per 100,000

Figure 1.3: Incidence of Active Tuberculosis by Year, Region of Peel and Ontario, 1992–2001

NA: 2000 and 2001 Ontario data not available.

Note: Rates age-standardized using 1991 (adjusted) Canadian population. Sources: Ontario data from RDIS, Ontario Ministry of Health and Long-Term Care, as of 07/17/2001.

Peel data from RDIS, Region of Peel Health Department, as of 07/22/2002.

Statistics Canada, Population Estimates and Projections distributed by the Ontario Ministry of Health and Long-Term Care.

Year

In Ontario in 2001, Peel was second only to Toronto for the number of

tuberculosis cases (see Figure 1.4).8

Figure 1.4: Active Tuberculosis Cases by Health Unit in Ontario, 2001

Sources: Peel data from RDIS, Region of Peel Health Department as of 07/22/2002.

Waterloo data from RDIS, Region of Waterloo Public Health as of 09/01/2002.

York Region data from RDIS, York Region Health Services Department as of 09/12/2002.

City of Hamilton data from RDIS, City of Hamilton Social and Public Health Services Department as of 09/16/2002.

City of Ottawa data from RDIS, City of Ottawa Public Health.

Toronto data from RDIS, Toronto Public Health, Communicable Disease Control Service as of 09/2002.

Number of Cases

Health unit

50 100 150 200 250 300 3500 400

Toronto

Peel

Ottawa

York Region

Hamilton

Waterloo

358358

9090

4646

3737

99

2121


Between 1980 and 1988, reported tuberculosis (TB) cases in Peel accounted for

about 6% of all TB cases in Ontario. Between 1992 and 1999, Peel accounted

for about 10% of Ontario’s TB cases.

From 1995 to 2000, Peel’s hospitalization rates for tuberculosis (TB) ranged

between three to five cases per 100,000. Twenty nine Peel residents died from

TB from 1990 to 1999; however, deaths due to the disease remain relatively rare.

Active Tuberculosis by Age and Sex

The incidence of tuberculosis (TB) varies with age, typically peaking among

those aged 60 years and older with a smaller peak among those aged 20 to 39

years (see Figure 1.5). Age-specific incidence was similar for all age groups in

Peel and Ontario, except for those aged 60 years and older. The incidence for

those 60 years and older was almost twice as high in Peel as in Ontario.

Sources: Ontario data from RDIS, Ontario Ministry of Health and Long-Term Care, as of 07/17/2001. Peel data from RDIS, Region of Peel Health Department, as of 07/22/2002.


Peel

Ontario

0–4 5–9 10–14 15–19 20–29 30–39 40–49 50–59 60+0

35

30

25

20

15

10

52.02.0 1.91.9

0.60.6 1.21.2 1.11.1 1.81.8

6.26.24.84.8

11.311.39.39.3

10.210.28.48.4 8.18.1

6.16.1

9.19.1

6.96.9

24.524.5

12.812.8

Figure 1.5: Incidence of Active Tuberculosis by Age Group, Region of Peel, 1992–2001 Combined, and Ontario, 1992–1999 Combined

Average annual cases per 100,000

Age Group (Years)


Active Tuberculosis by Country of Birth

Immigrants to Canada from countries with higher tuberculosis (TB) rates

(TB-endemic countries) face a greater likelihood of developing active TB

during their first five years in Canada than Canadian-born individuals.3,4

In Peel from 1992 to 2001, the proportion of tuberculosis (TB) cases among

foreign-born individuals increased from 89% to 97%. The proportion of

foreign-born TB cases in Peel was higher than Ontario for every year from

1992 to 1999 (see Figure 1.7 on the following page).

The higher proportion of foreign-born cases in Peel may be due to the higher

proportion of immigrants in Peel compared to Ontario (40% and 26%,

respectively [1996 Census]) and the higher proportion of recent immigrants

in Peel from TB-endemic countries. In 1996, Peel had a larger proportion of

its population (9%) who had immigrated to Canada in the previous five

years than Ontario (5%).

In Peel, the incidence of tuberculosis (TB) for males and females was similar

among all age groups except those 60 years and older (see Figure 1.6).

Although not shown, the average annual crude rate of TB in Peel was 9.4

per 100,000 for males and 9.0 per 100,000 for females.

0–4 5–9 10–14 15–19 20–29 30–39 40–49 50–59 60 up0

35

30

25

20

15

10

52.72.7

1.41.40.30.3 0.90.9 0.30.3

1.81.8

6.86.85.55.5

12.112.110.510.5 9.99.9 10.610.6

7.57.58.88.8

10.110.18.18.1

20.620.6

29.229.2

Figure 1.6: Incidence of Active Tuberculosis by Age Group and Sex, Region of Peel, 1992–2001 Combined

Sources: Peel data from RDIS, Region of Peel Health Department, as of 07/22/2002.


Average annual cases per 100,000

Age Group (Years)

Female

Male


Peel

Ontario

NA: 2000 and 2001 Ontario data not available.

Sources: Ontario data from RDIS, Ontario Ministry of Health and Long-Term Care, as of 07/17/2001. Peel data from RDIS, Region of Peel Health Department, as of 07/22/2002.

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

89% 89% 91% 89% 94% 94% 94% 93% 96% 97%

0

100

80

60

40

20

75% 78% 81% 81% 85% 83% 82% 84% NA NA

Per cent of foreign-born cases

Figure 1.7: Proportion of Active Tuberculosis Cases Born Outside Canada, Region of Peel and Ontario, 1992–2001

Year

Figure 1.8: Proportion of Active Tuberculosis Cases by Country of Birth, Region of Peel, 1992–2001 Combined, and Ontario, 1992–1999 Combined

Per Cent of Active Tuberculosis Cases

Country of birth

5 10 15 20 25 30 350

India 9%9%31%31%

Philippines 8%8%14%14%

Vietnam 10%10%13%13%

Canada 17%17%7%7%

Pakistan 2%2%5%5%

Hong Kong 5%5%4%4%

China(other than

Hong Kong)

8%8%3%3%Sources: Ontario data from RDIS, Ontario

Ministry of Health and Long-Term Care, as of 07/17/2002.


Peel

Ontario


In Peel between 1992 and 2001, the most common countries of birth

among tuberculosis (TB) cases included India (31%), the Philippines (14%),

Vietnam (13%) and Canada (7%) (see Figure 1.8 on the previous page). The

percentage of TB cases in individuals born in India was significantly higher

in Peel between 1992 and 2001(31%) than in Ontario between 1992 and

1999 (9%), while the percentage of Canadian-born cases was significantly

higher for Ontario (17%) compared to Peel (7%) (see Figure 1.8 on the

previous page).

Citizenship and Immigration Canada (CIC) screens immigrants for

tuberculosis (TB) and permits those with evidence of inactive, pulmonary

TB to enter Canada on the condition they report to health authorities within

30 days.9 The annual number of immigrant notifications for TB follow-up

received by the Region of Peel Health Department are presented in Figure

1.9. The annual number of notifications has fluctuated from year to year,

although the number has steadily increased from 1998 to 2001. The sudden

increase from 2000 to 2001 can be partly explained by improved reporting.

19920

1,200

1,000

800

600

400

200

Figure 1.9: Immigration Notifications for Inactive Tuberculosis Follow-up, Region of Peel, 1992–2001

Source: Peel Data from RDIS, Region of Peel Health Department as of 07/22/2002.

Number of notifications

Year

336336

1993

361361

1994

526526

1995

816816

1996

730730

1997

582582

1998

309309

1999

382382

2000

492492

2001

1,0181,018


Risk Factors and Risk Settings for ActiveTuberculosis

A “risk factor” is the most likely explanation for a particular person’s

progression from inactive to active tuberculosis (TB). “Risk setting” refers to

the location where transmission most likely occurred. Figures 1.10 and 1.11

present the risk factors and risk settings for TB cases in Peel. “Unknown risk

factor” was reported for 65% of all TB cases in Peel. The three most reported

known risk factors were having previous, inactive disease (12%) or an

underlying medical condition (11%), and being in close contact with an

individual with active TB (11%) (see Figure 1.10).

Per cent based on 832 tuberculosis cases. A case could be reported with more than one risk factor.

Source: RDIS, Region of Peel Health Department as of 07/22/2002.

Figure 1.10: Risk Factors Reported for Active Tuberculosis Cases, Region of Peel, 1992–2001 Combined

Per Cent of Cases

Risk factor

10 20 30 40 50 60 700

Unknown

Inactive Disease

UnderlyingMedical Condition

Close Contact

Other

HIV/AIDS

6565

1212

1111

1111

22

22

In Peel from 1992 to 2001, travel to or living in a tuberculosis-endemic

country was the most often reported risk setting (79%) reported by individuals

with TB (see Figure 1.11 on the following page). Very few cases of TB arose as

a result of exposure at work or school.


Anatomic Site of Active Tuberculosis

Most people with active tuberculosis (TB) develop the disease in their lungs

(pulmonary TB). People with non-pulmonary TB can develop the disease in

their brain, kidneys, skin, bones, joints or lymph nodes. Non-pulmonary TB

is more common in areas of the world where TB is prevalent.3

The lungs were the most commonly reported anatomic site of tuberculosis

(TB) infections, followed by the lymph nodes, in cases in both Peel and

Ontario. In Peel for the years 1992 to 2001, 51% of reported infection sites

were pulmonary (see Figure 1.12 on the following page). In Ontario in 1998,

61.4% of TB cases were reported as pulmonary.8

In Peel, non-pulmonary tuberculosis (TB) was reported more frequently in

foreign-born individuals than in Canadian-born individuals (see Figure 1.13

on the following page).

Figure 1.11: Risk Settings Reported for Active Tuberculosis Cases, Region of Peel, 1992–2001 Combined

Per cent based on 832 tuberculosis cases.

Source: RDIS, Region of Peel Health Department, as of 07/22/2002.

Per Cent of Cases

Risk settings

10 20 30 40 50 60 70 80 900

Travel/EndemicCountry

Home

7979

1111

Unknown 44

School 22

Hospital 11

Workplace 11

CorrectionalFacility 11


Based on 888 sites reported by 832 tuberculosis cases in Peel from 1992 to 2001.


Figure 1.12: Active Tuberculosis Cases by Anatomic Site, Region of Peel, 1992–2001 Combined

Pulmonary 51%Pulmonary 51%

Central Nervous System 2%Central Nervous System 2%

Miliary 2%Miliary 2%

Abdominal 2%Abdominal 2%

Other 3%Other 3%

Bone and Joint 4%Bone and Joint 4%

Genitourinary 5%Genitourinary 5%

Pleura 8%Pleura 8%Lymph Node 23%Lymph Node 23%

Figure 1.13: Active Tuberculosis Cases by Anatomic Site and Place of Birth, Region of Peel, 1992–2001 Combined

Per Cent of Cases by Site

Site of tuberculosis

10 20 30 40 50 60 70 80 900

Pulmonary 53538080

55

55

55

33

22

22

22

Lymph Node 2626

CentralNervous System

22

Pleura 99

Genitourinary 55

Bone and Joint 55

Miliary 22

Other

Based on 60 Canadian-born and 772 foreign-born tuberculosis cases. Some cases may have reported more than one site.


Foreign-born

Canadian-born

66


Drug-Resistant Tuberculosis

Drug resistance arises when medication is improperly prescribed or taken.3

A tuberculosis (TB) case is defined as being drug-resistant if the strain of

TB causing the disease is resistant to one or more of the five first-line

drugs: isoniazid, rifampin, pyrazinamide, ethambutol and streptomycin.10

Resistance prolongs treatment by at least three months. Resistance to at least

isoniazid and rifampin—the two best TB drugs—is called multi-drug resistant

tuberculosis (MDR-TB). MDR-TB is treated using second-line drugs (drugs

other than the five, first-line drugs mentioned above). Second-line drugs are

more expensive, less effective and have many more side effects than first-line

drugs. As a result, treatment of MDR-TB continues for at least two years

and must be closely monitored.

In Peel from 1992 to 2001, a total of 85 tuberculosis (TB) cases were resistant

to one or more drugs. Drug resistance as a proportion of total TB cases

fluctuated widely from year to year (see Figure 1.14).

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

2% 15% 10% 18% 11% 7% 10% 19% 3% 12%

0

25

20

15

10

5

7% 8% 10% 9% 9% 11% 9% 13% NA NA

Peel

Ontario

Per cent of total tuberculosis cases*

Figure 1.14: Proportion of Drug-Resistant Tuberculosis by Year, Region of Peel and Ontario, 1992–2001

NA: 2000 and 2001 data not available.

* Per cent based on total tuberculosis cases for each year in Peel and Ontario.

Sources: Ontario data from RDIS, Ontario Ministry of Health and Long-Term Care, as of 07/17/2001.


Year


In Peel from 1992 to 2001, 74% of all tuberculosis (TB) cases reported

drug sensitivity patterns. Twenty-six per cent of TB cases were classified

as “unspecified” (see Figure 1.15). Unspecified cases are those for which TB

specimens could not be cultured to obtain information on drug resistance.

Ten per cent of total TB cases in Peel were classified as drug-resistant.

Resistance to isoniazid, one of the two best anti-TB drugs, occurred in 73% of

Peel’s resistant cases. Resistance in these cases occurred with isoniazid alone

or in combination with resistance to another drug. Multi-drug resistant TB is

especially troublesome and occurred in 7% of all drug-resistant cases in Peel.

Figure 1.15: Drug-Resistant Tuberculosis Cases, Region of Peel, 1992–2001 Combined

Based on 832 tuberculosis cases.


Sensitive (64%)Sensitive (64%) Streptomycin (SM) (14%)

Streptomycin (SM) (14%)

INH + SM (15%)INH + SM (15%)

Multi-drugresistant (7%)

Multi-drugresistant (7%)

INH + SM + other (6%)INH + SM

+ other (6%)

INH + other (6%)

INH + other (6%)

Pyrazinamide (6%)

Pyrazinamide (6%)

Isoniazid (INH) (46%)Isoniazid (INH) (46%)

Unspecified (26%)Unspecified (26%)

Resistant to drugs (10%)Resistant to drugs (10%)

Multiple drug-resistant tuberculosis (MDR-TB) is the result of poor

treatment of active TB. Physicians’ inadequate prescribing of antibiotics

and patients’ non-compliance with treatment all contribute to MDR-TB.11

In addition, the speed of air travel has increased the movement of people

around the world and the possibility of importing drug-resistant TB into

Canada.11 Various studies have noted that foreign birth is a significant factor

associated with drug resistance.11

Poor compliance with anti-tuberculous therapy is the most common reason

for treatment failure. Directly Observed Therapy (DOT), in which a trained

individual observes the tuberculosis (TB) patient swallow each dose of

medication, is an effective way to monitor adherence with therapy.12 TB drug

regimes using DOT have been shown to significantly reduce the rate of drug

resistance and the rate of relapse when compared to self-administered therapy.12

Communicable Disease Report 2002 - Focus on Tuberculosis ...

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