Eurosurveillance

ECDC

Tendencies of Tuberculosis Incidence in Estonia, 1998-2006

 Rediger
  Published: 26.09.07 Updated: 26.09.2007 11:48:39

V. Hollo. National Tuberculosis Registry, Estonia

 

Background

The high incidence of tuberculosis (TB) has been a serious public health problem since Estonia regained independence in 1992. Although we have experienced a steady decline in the incidence of TB over the last 6 years, Estonia is still one of the “leaders” in the European Union in respect to spread of TB- and HIV-infection, both epidemic diseases. The incidence of TB in Estonia is five times higher than in the Nordic countries and only Latvia and Lithuania have reported higher incidences than Estonia.

TB incidence

In the 1990s the incidence of new TB cases and relapses increased approximately 10% every year, from 26 cases per 100 000 population (in 1991), reaching a maximum in 1998 of 59.2 cases per 100 000. Thereafter the annual incidence of TB gradually decreased. The incidence was stable during 2001 and 2002 with 51.9 and 47.7 notified cases per 100 000, respectively. Since 2002 the incidence has decreased by 5%-10% annually to 27.8 new TB cases per 100 000 in 2006.

Figure 1. Tuberculosis incidence per 100 000 population, 1989 - 2006

Figure 1

 
 
 
 
 
 
 
 
 
Figure 2. TB cases in Estonia, 1989 - 2006

Figure 2

 
 
 
 
 
 
 
 
TB distribution by gender and age

There were 249 men among the TB patients (67.8%) in 2006. The incidence per 100 000 was 40.3 among men and 16.3 among women, respectively, i.e. 2.5 times lower among women. From 1998 to 2006 the incidence among men has decreased by 2.3 times. In women the reduction is only 1.6 times. Thus the incidence of tuberculosis is decreasing more rapidly among men as illustrated in figure 4.

Figure 3. New TB cases by age group and gender, 2006 Figure 3
 
 
 
 
 
 
Figure 4. TB cases by gender and proportion of females, 1998 - 2006 Figure 4
 
 
 
 
 
TB in children

TB in children aged 0–14 years differs from TB in adults with respect to general indicators (lower confirmation rate) and localisation (lower percentage of pulmonary TB) of the disease. The incidence among children was 3 (in 2000) to 30 (in 2005) times less frequent than in the population in general (fig. 5). The TB incidence among children has decreased considerably since 1998. The proportion of disease among girls and boys is 55% and 45%, respectively. The situation was different in 2006; 5 boys and 3 girls were diagnosed with TB.
Culture-positive (confirmed TB) cases in children have been diagnosed rarely compared with adults. A total of 76 TB cases in children only 7 were been bacteriologically confirmed (9.2%).

Figure 5. Tuberculosis in children, 1998-2006
Figure 5
 
 
 
 
 
 
Pulmonary TB

402 cases of pulmonary TB were notified in Estonia (i.e. 91.8% of total TB cases) in 2006. Among these, 316 cases (79.2% of the total cases) were culture-positive.
In addition to new and relapse TB cases, clinically diagnosed relapses and retreatment cases are notified  based only on clinical criteria (in 2006 – 86 cases).
Consequently, certain differences in the incidence of TB are possible from WHO statistics.
Three-quarters of all pulmonary TB cases have been confirmed by bacterial culture during the last 8 years in Estonia.
The proportion of smear-positive TB cases was approximately 45% of all tuberculosis cases in 1998 – 2006.

Table 1. Bacteriologically confirmed cases of pulmonary TB, 1998 – 2006  

 

Year / Год

Total / Всего

1998

1999

2000

2001

2002

2003

2004

2005

2006

Culture+ / Посев +

520

510

517

458

441

388

394

346

316

3886

%  of tested / %  обследованных

69.1

74.6

72.4

75.6

79.0

76.4

79.8

78.3

79.2

76.0

Table 2.  Smear-positive cases of pulmonary TB, 1998 - 2006

 

Year / Год

Total / Всего

1998

1999

2000

2001

2002

2003

2004

2005

2006

Smear+ / Мазок +

371

307

316

267

255

228

236

191

177

2348

%  of tested / %  обследованных

54.0

41.1

43.8

43.3

45.2

44.4

47.2

42.4

44.0

45.1

Treatment outcomes in culture-positive non MDR-TB (multi-drug resistant) cases

 The WHO target for TB treatment outcomes by 2005 was a success rate of 85%. Estonia has almost achieved this goal.

M. tuberculosis drug resistance

According to the tuberculosis registry data, M. tuberculosis drug resistance was analysed in strains isolated from 331 patients during 2006. In 102 cases (30.8%) drug resistance was observed against at least one first-line antituberculosis drug. According to the general practice in Estonia, M. tuberculosis drug resistance was tested with 4 first-line  and 5 second-line antituberculosis drugs.
The prevalence of the drug resistance was: 
streptomycin –  86 strains (27.5%)
ethambutol –    44 strains (14.2%)  
isoniazide –    76 strains (22.9%)  
rifampicin–    49 strains (14.8%) 

Figure 6. Treatment outcomes of confirmed pulmonary TB cases, 1998-2005 Figure 6
 
 
 
 
 
 
MDR tuberculosis

MDR-TB means M. tuberculosis is simultaneously resistant to isoniazide and rifampicin.
During the last years Estonia has had one of the highest incidences of M. tuberculosis drug resistance, and especially MDR-TB.
The DOTS Plus treatment system, MDR-TB case treatment with second line drugs, was implemented in Estonia in 2001.
In 2006, 33 (12.7%) of new TB cases and 47 (14.2%) of all bacteriologically confirmed (331 cases culture-positive) TB cases were multi-drug resistant (at least isoniazide and rifampicin).

Table 3. Total number and percentage of MDR-TB pulmonary and extrapulmonary cases

 

2001

2002

2003

2004

2005

2006

Total / Всего

MDR TB cases / Больные МЛУ ТБ

98

100

83

71

68

47

467

% of tested / % обследованных

20.2

21.2

19.6

16.9

18.4

14.2

18.7

Table 4. Percentage of new and relapse MDR-TB cases

Primary MDR / Первичная МЛУ

2001

2002

2003

2004

2005

2006

Total / Всего

No / Кол-во

53

64

51

51

42

36

297

% of tested / % обследованных

14.1

17.1

14.3

14.2

13.3

12.9

14.4

Acquired MDR / Приобретенная МЛУ

  

No / Кол-во

45

36

32

20

26

11

170

% of tested / % обследованных

42.1

37.5

48.5

32.3

47.3

21.2

38.8

MDR-TB treatment outcomes monitoring

Treatment success in MDR-TB cases is much lower than in susceptible TB cases. This is primarily due to a higher default rate. This represents one of the biggest challenges for the National Tuberculosis Programme.

Figure 7. MDR-TB treatment outcomes, 2001 – 2004 Figure 7
 
 
 
 
 
Extrapulmonary tuberculosis

The percentage of extrapulmonary TB has slowly decreased.
In 2006, 36 cases of extrapulmonary tuberculosis were notified, including 31 new cases and 5 relapses. Fifteen (41.6%) cases of extrapulmonary tuberculosis were bacteriologically confirmed. More than half of the cases were diagnosed on the basis of clinical signs and symptoms.
Extrapulmonary cases included TB pleurisy (16 cases), bone and joint TB (9 cases), TB of genitourinary tract (5 cases), TB of thoracic- and peripheral lymph nodes (2 cases) and TB meningitis (2cases).
Unlike pulmonary tuberculosis, older age groups dominated among patients with extrapulmonary tuberculosis. The incidence among females of younger age groups exceeds the morbidity among males.
In 2006, 15 women (41.4%) and 21 men (58.6%) were notified as having an active form of extrapulmonary tuberculosis. Only one case of multi-drug resistant extrapulmonary TB was registered in 2006. This case was a patient with tuberculosis pleuritis, and a multi-resistant strain of M. tuberculosis was isolated from the pleural effusion fluid.

Table 5. Prevalence of extrapulmonary TB, 2001 - 2006

 

2001

2002

2003

2004

2005

2006

No./ Кол-во

91

83

66

61

51

36

% from all TB cases / % от всех случаев ТБ

12.9

12.8

11.4

10.9

10.2

8.2

Figure 8. Extrapulmonary TB cases by gender and age groups, 2006Figure 8
 
 
 
 
HIV-positive TB patients

Worldwide, infection with the human immunodeficiency virus (HIV) has been one of the most important risk factors for tuberculosis during recent years. In Estonia, HIV infection has been notified in approximately 2.5% of all TB cases. However, taking into consideration the rapid increase in the number of HIV-positive individuals in Estonia, it can be expected that the number of HIV-positive tuberculosis patients will also start to increase. To date the statistics of HIV-positive tuberculosis patients in Estonia is as follows: in total 147 new and relapse cases in 127 individuals, including 14 HIV-positive patients with relapse of tuberculosis. Until 2001, all notified HIV-positive patients with tuberculosis were male (in total 99 ). Among women TB/HIV co-infection has been notified in 29 cases. Among persons aged 18-58 years the mean age for TB patients at the time of  HIV diagnosis was 31.2 years. Extrapulmonary cases have been diagnosed in 13.2% and MDR-TB cases in 16.3% of all confirmed cases.
The mean age of TB patients with negative HIV test results has been stable over the past 5 years. At the same time the mean age of HIV-infected TB patients has increased 10%.
Among HIV-positive tuberculosis patients notified in 2006, extrapulmonary TB was observed in 3 (7.7%) patients (1 tuberculosis pleurisy and tuberculosis meningitis in 2 patients). MDR-TB was registered in 4 cases (10.3%).

Table 6. Distribution by gender of HIV-positive tuberculosis patients, 1997 - 2006

Gender / Пол

Year / Год

Total / Всего

1997

1999

2000

2001

2002

2003

2004

2005

2006

M / M

1

1

1

7

12

9

17

25

27

100

F / Ж

0

0

0

0

5

4

4

7

7

27

Total / Всего

1

1

1

7

17

13

21

32

34

127

Table 7. Mean age of HIV-negative  TB patients and HIV-positive TB patients, 2001 – 2006

TB cases / Больные ТБ

2001

2002

2003

2004

2005

2006

HIV-neg TB cases / ВИЧ-отриц.

46.6

46.8

46.2

46.8

46.2

46.7

HIV-pos TB cases / ВИЧ-положит.

29.8

28.1

30.3

29.8

33.6

32.9

Conclusion

The TB incidence rates in Estonia have decreased remarkably over the last 5 years. However, warning signs such as high drug resistance and high HIV-prevalence demand continuous efforts to make the decrease irreversible. High default rates, especially in MDR- TB cases, is another challenge that tuberculosis treatment institutions in Estonia must overcome.













 

 

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