Guidelines for Tuberculosis Control in New Zealand 2003
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Guidelines for Tuberculosis Control in New Zealand 2003 Citation: Ministry of Health. 2002. Guidelines for Tuberculosis Control in New Zealand 2003. Wellington: Ministry of Health. Published in December 2002 by the Ministry of Health PO Box 5013, Wellington, New Zealand ISBN: 0-478-25593-4 (Website) This document is available on the Ministry of Health’s website: http://www.moh.govt.nz Chapter 1: The Epidemiology and Surveillance of Tuberculosis in New Zealand Dr Fiona Turnbull Public Health Medicine Registrar, Ministry of Health Contents Summary 2 Introduction 3 1.1 Epidemiology of TB 4 1.1.1 Trends in incidence 4 1.1.2 Outbreaks 5 1.1.3 Incidence by health district 5 1.1.4 Incidence by age 7 1.1.5 Incidence by gender 8 1.1.6 Incidence by ethnicity 8 1.1.7 Incidence by place of birth 9 1.1.8 Social vulnerability as a risk factor for TB 10 1.1.9 Other risk factors 10 1.2 Type, management and outcome of notified TB cases 12 1.2.1 Laboratory confirmation 12 1.2.2 Site of infection 12 1.2.3 Morbidity and mortality 13 1.2.4 Directly observed therapy (DOT) 14 1.2.5 Antibiotic resistance 15 1.3 Surveillance of TB 17 1.3.1 Objectives 17 1.3.2 Definitions of terms used in surveillance 17 1.3.3 Notification and data collection 18 1.3.4 Completeness of notification 19 1.3.5 Population surveillance 20 1.4 Recommendations and future developments 20 Appendices Appendix 1.1: Excerpt from Public Health Surveillance in New Zealand Manual 22 Appendix 1.2: Tuberculosis Case Report Form 27 Appendix 1.3: Proposed TB Surveillance Information Flows 30 References 31 Guidelines for Tuberculosis Control in New Zealand 2003 1 Chapter 1: The Epidemiology and Surveillance of Tuberculosis in New Zealand Summary TB epidemiology The current TB notification rate in New Zealand is 10 per 100,000. Incidence has increased slightly in recent years. Higher rates of disease in New Zealand compared with other developed countries may be attributed to socioeconomic deprivation and immigration from high-incidence countries. Over half of all TB cases are in foreign-born individuals. The highest rates of disease are seen in: – urban areas, particularly Auckland and South Auckland – older adults aged 70 years – individuals of non-European ethnicity, particularly ‘Other’ and Pacific. Contact with a known TB case is an important risk factor for the disease. Outbreaks of TB occur. Type, management and outcome of TB cases Two-thirds of TB cases are pulmonary. Of the extra-pulmonary cases, the most common sites of infection are lymph nodes. Morbidity and mortality from TB have been declining in recent years. Mortality rates are highest among older individuals ( 70 years) but vary by ethnicity. Information on directly observed therapy (DOT) is poorly recorded by most health districts, where the information is recorded. Multi-drug resistance accounts for only 1% of all TB isolates. Surveillance of TB Surveillance is important for supporting local management of the disease, monitoring disease incidence and identifying risk factors. Any medical practitioner diagnosing or suspecting a case of new or relapsed TB is required, under the Tuberculosis Act 1948, to notify the case to the local medical officer of health. EpiSurv data entry should ideally be done by the Public Health Service after liaison with the reporting clinician. Although people receiving treatment for latent TB infection are not legally required to be notified, clinicians are requested to notify them to the medical officer of health for monitoring purposes. Recent changes to surveillance include: – alterations to the Tuberculosis Case Report Form (see Appendix 1.2) – DNA fingerprinting of all isolates. Suggested improvements to the current system include: – developing methods to identify unnotified cases – regular review of surveillance data to inform policy. 2 Guidelines for Tuberculosis Control in New Zealand 2003 Chapter 1: The Epidemiology and Surveillance of Tuberculosis in New Zealand Introduction In this chapter we: review the epidemiology of TB in New Zealand using EpiSurv notification data from 1995 to 2001 describe the system of TB surveillance adopted in New Zealand from November 2002 outline some recommendations for improving the current system of TB surveillance. The most thorough recent review of TB epidemiology in New Zealand is provided by J Carr et al. The Epidemiology of TB in New Zealand, 1995–1999.12 The information in this chapter was obtained from that review and from ESR data. Guidelines for Tuberculosis Control in New Zealand 2003 3 Chapter 1: The Epidemiology and Surveillance of Tuberculosis in New Zealand 1.1 Epidemiology of TB 1.1.1 Trends in incidence Compulsory notification for all forms of TB was introduced in New Zealand in 1940.1 Notifications peaked in 1943 with 2600 cases, a rate of 159 per 100,000 (see Figure 1.1). After a peak in cases around the time of the Second World War there was a steady decline in disease incidence. Figure 1.1: Tuberculosis notification rates, 1948–2001 180 Notification rate per 100,000 160 140 120 100 80 60 40 20 0 1940 1944 1948 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000 Year TB incidence reached its lowest point in 1988, with 295 notified cases. Since this time between 300 and 500 cases have been notified annually, with some evidence that incidence is increasing slightly (see Figure 1.2). A similar trend has been observed in other developed countries and is related to HIV/AIDS, immigration from high-incidence countries, and the deterioration of control programmes.2 4 Guidelines for Tuberculosis Control in New Zealand 2003 Chapter 1: The Epidemiology and Surveillance of Tuberculosis in New Zealand Figure 1.2: Trend in tuberculosis incidence, 1988–2001 Notification rate per 100,000 Notification rate per 100,000 12.0 Trend line 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Year The current average annual rate of TB in New Zealand of around 10 per 100,000 is comparable to that reported from the UK (10 per 100,000), but is higher than that reported from the US (6 per 100,000), Canada (7 per 100,000) and Australia (5 per 100,000).3 Although the validity of international comparisons is limited by variations in case detection and reporting practices, higher rates in this country have raised concerns about the effectiveness of current prevention and control activities. Sociodemographic factors such as poverty, overcrowding and migration from countries of high incidence have been identified as contributing to disease resurgence in New Zealand.4 1.1.2 Outbreaks An estimated 10% of all notified cases occur as part of recognised TB outbreaks. Accurate reporting of outbreak-related cases of TB is limited by incomplete recording of outbreak numbers on EpiSurv. In 2001 there were five reported outbreaks of TB, with an average of 2.8 cases per outbreak. Large outbreaks involving between 12 and 61 cases have previously occurred in a church group, a prison and in schools. 1.1.3 Incidence by health district Within New Zealand several health districts report consistently high rates of disease. Auckland (23.0 per 100,000) and South Auckland (19.0 per 100,000) report the highest rates, followed by Wellington (15.1 per 100,000) and the Hutt (13.6 per 100,000) (see Table 1.1 and Figure 1.3). High rates in these cities are consistent with overseas findings that disease tends to persist in urban areas5 and with the geographic distribution of ethnic groups most affected by the disease. Guidelines for Tuberculosis Control in New Zealand 2003 5 Chapter 1: The Epidemiology and Surveillance of Tuberculosis in New Zealand Several studies have examined the epidemiology of TB in the Auckland6 7 8 and Wellington regions.9 10 Clustering of cases in areas of socioeconomic deprivation within these health districts and the importance of immigration from countries with a high prevalence of TB has been noted in both areas. Table 1.1: TB notifications, by health district, 1995–2001 Health district Total number of cases Average annual notification (1995–2001) rate per 100,000 Northland 90 9.4 Northwest Auckland 260 9.4 Auckland 557 23.0 South Auckland 454 19.0 Waikato 133 6.3 Tauranga 51 6.5 Eastern BOP 31 8.8 Rotorua 29 6.4 Gisborne 17 5.3 Taupo 22 10.2 Ruapehu 12 10.2 Taranaki 15 2.0 Hawke’s Bay 81 8.1 Wanganui 31 7.2 Manawatu 71 6.7 Wairarapa 12 4.5 Wellington 257 15.1 Hutt 126 13.6 Nelson–Marlborough 18 2.2 West Coast 7 3.1 Canterbury 197 7.3 South Canterbury 19 3.4 Otago 58 4.8 Southland 32 4.1 6 Guidelines for Tuberculosis Control in New Zealand 2003 Chapter 1: The Epidemiology and Surveillance of Tuberculosis in New Zealand Figure 1.3: TB notification rates, by health district, 1995–2001 1.1.4 Incidence by age The majority of TB cases occur in adults, with the highest rates in those aged 70 years and above (see Table 1.2). Children aged under 15 years account for between 6% and 10% of all cases, but this proportion varies significantly by ethnicity (European 3%, Mäori 15%, Pacific peoples 17%, Other 6%). Although the incidence of TB in children remains low, there has been no reduction in recent years.11 Guidelines for Tuberculosis Control in New Zealand 2003 7 Chapter 1: The Epidemiology and Surveillance of Tuberculosis in New Zealand Table 1.2: TB notifications, by age group, 1995–2001 Age group (years) Proportion of all Average annual age-specific cases (%) rate per 100,000 < 1 0.8 5.2 1–4 4.4 7.3 5–9 3.0 3.9 10–14 3.1 4.4 15–19 5.1 7.2 20–29 18.6 12.7 30–39 16.8 10.8 40–49 11.1 8.3 50–59 10.2 11.0 60–69 11.2 15.6 70+ 15.6 20.1 1.1.5 Incidence by gender There are no marked gender differences in the incidence of TB in New Zealand.