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Tuberculosis

Mycobacterium tuberculosis
 

General information


Tuberculosis (TB) is a curable infectious disease caused by the tubercle bacillus 'Mycobacterium tuberculosis' or 'M. tuberculosis'.
 
TB causes more deaths worldwide than any other single infectious disease and was declared a 'global emergency' by the World Health Organization in 1993. Nine million new cases of active TB and nearly two million deaths from TB, are estimated to occur around the world every year.
  
TB in Wales, and other industrialised nations, declined rapidly last century but never went away. Nearly all countries in the world are now affected by the global resurgence of TB driven primarily by poverty and poor access to health services, migration and HIV. However, TB remains rare in Wales and incidence has changed little in the last decade.
 
TB bacilli are slow growing and can survive in the body for many years in a dormant or inactive state whereby people are infected but show no signs of TB disease. When the bacillus is dividing people are said to have 'active TB'.
  
X-ray of the lungs of a patient with pulmonary tuberculosisTB usually causes disease in the lungs (pulmonary), but can also affect other parts of the body (extra-pulmonary). Only the pulmonary form of TB disease is usually infectious. Transmission occurs through coughing of infectious droplets, and usually requires prolonged close contact with an infectious case. The most important part of controlling TB is identifying and treating those who already have the disease, to shorten their infection and to stop it being passed on to others.
  
Cure is usually by treatment with a combination of specific antibiotics which must be taken for at least six months. Resistance to these drugs is an increasing problem worldwide, most particularly in developing countries, due to inadequate treatment. This makes TB much harder to treat. Multi-drug resistant TB (MDR-TB) describes TB strains that are resistant to two of the main drugs used for treatment. Extensively drug resistant TB (XDR-TB), where TB strains are resistant to many other drugs used for treatment, is now recognised. In 2010 MDR-TB accounted for only 1.3% of UK cases with an even a smaller proportion of these being classed as XDR-TB. 
 
TB in humans can also occasionally be caused by another bacterium, Mycobacterium bovis, which is particularly associated with infection in cattle and is usually transmitted to humans through contaminated milk.
 
However,the current risk posed by M. bovis to human health in the UK is considered negligible due to effective controls through milk pasteurisation and tuberculin screening of herds to identify infected animals. More information about M. bovis including surveillance data for Wales is available from the webpage: Mycobacterium bovis (Bovine TB).
 
Information about treatment and prevention of tuberculosis is available from the main Public Health Wales website by following the link: http://www.wales.nhs.uk/sitesplus/888/page/43877
 
More information about TB is also available from the following websites:

 

Surveillance of tuberculosis in Wales  


Enhanced Tuberculosis Surveillance commenced on 1 January 1999 in England and Wales, and the following year in Northern Ireland, with the aim of continually providing detailed and comparable information on the epidemiology of tuberculosis and specifically to enable more precise estimates of trends in tuberculosis incidence in subgroups of the population. 
 
The minimum dataset includes notification details, demographic, clinical and microbiological information on all cases of tuberculosis in Wales reported by clinicians to local health protection teams, then via Public Health Wales CDSC to Public Health England in Colindale.
 
Enhanced Tuberculosis Surveillance provides an annual corrected analysis of reports by age, sex, ethnic group, country of birth, site of disease and region.
 
The latest surveillance report for Wales, published in December 2013, is available from the link: Enhanced TB Surveillance Annual Report for Wales: Data to end of 2012 [Pdf, 516KB]
  
All previous reports for Wales are available from the link: Enhanced TB Surveillance Annual Reports for Wales
 
The latest surveillance report of TB in the UK was published by Public Health England in August 2013 and is available from the link: Tuberculosis in the UK: 2013 report
    
Notification data: Real time data for the notification of clinically diagnosed tuberculosis are available from the link: Interactive Trend Data for Wales. However, with notiifcation data it is difficult to accurately identify duplicate forms received from more than one physician involved in the management of the same incident case, and to completely exclude through de-notification cases wrongly diagnosed as tuberculosis. As a result, numbers of cases reported annually through notifications differ from the number of cases reported through more rigorously checked National Surveys and Enhanced Tuberculosis Surveillance. Therefore trends in tuberculosis notifications should be interpreted with caution. 
 
 

Recent trends in Wales 2003-2013


Tuberculosis cases and rates in Wales by sex reported by Enhanced TB Surveillance 2003-2013
   
 
Male
Female
All TB in Wales
Year
Number of cases
Rate per 100,000 population
Number of cases
Rate per 100,000 population
Number of cases
Rate per 100,000 population
2003
105
7.4
59
3.9
164
5.6
2004
109
7.6
79
5.2
188
6.4
2005
99
6.8
87
5.7
186
6.3
2006
110
7.6
72
4.7
182
6.1
2007
114
7.8
90
5.9
204
6.8
2008
93
6.3
70
4.5
168*
5.6
2009
123
8.3
86
5.5
214*
7.0
2010
93
6.2
58
3.7
153**
5.0
2011
70
4.7
57
3.7
130***
4.2
2012
92
6.1
44
2.8
136
4.4
2013# - - - - 129 4.2
* includes 5 cases where gender is unknown
** includes 2 cases where gender is unknown
*** includes 3 cases where gender is unknown
# provisional data released16/12/2013
Source: Enhanced TB Surveillance Programme, CDSC Wales. 
 
Tuberculosis cases and rates in Wales reported by Enhanced TB Surveillance 2003-2012
TB in Wales chart
Source: Enhanced TB Surveillance Programme, CDSC Wales.
 
 
Tuberculosis rates in the UK reported by Enhanced TB Surveillance 2013
 TB rate in UK 2013 
Source: Enhanced TB Surveillance Programme, CDSC Wales and Pubic Health England
   
A report of TB surveillance data for Wales from 2003-2012 is available to download from: Enhanced TB Surveillance Annual Report for Wales: Data to end of 2012 [Pdf, 516KB]
       
Additional trend data supplied in the report includes:
  • Cases and rates of TB in Wales by age, sex and ethnicity 
  • Cases and rates of TB in Wales by Local Authority and by Health Board 
  • Cases of TB in Wales by place of birth (UK or abroad)
  • Tuberculosis cases in Wales by site of TB, previous diagnosis of TB and bacteriological results
  • Treatment outcomes
 

Epidemiology


Despite the availability of highly efficacious treatment for decades, TB remains a major global health problem. In 1993, the World Health Organization (WHO) declared TB a global public health emergency, at a time when an estimated 7–8 million cases and 1.3–1.6 million deaths occurred each year. In 2010, there were an estimated 8.5–9.2 million cases and 1.2–1.5 million deaths (including deaths from TB among HIV-positive people). TB is the second leading cause of death from an infectious disease worldwide (after HIV, which caused an estimated 1.8 million deaths in 2008). [WHO Report 2011 Global Tuberculosis Control, http://www.who.int/tb/publications/global_report/en/index.html]
 
TB is a worldwide pandemic; Most of the estimated number of cases in 2010 occurred in Asia (59%) and Africa (26%); smaller proportions of cases occurred in the Eastern Mediterranean Region (7%), the European Region (5%) and the Region of the Americas (3%).
 
The five countries with the largest number of incident cases in 2010 were India (2.0–2.45 million), China (0.9–1.2 million), South Africa (0.40–0.59 million), Indonesia (0.37–0.54 million) and Pakistan (0.33-0.48 million). India alone accounts for over a quarter (26%) of all TB cases worldwide, and China and India combined account for 38%.
 
There are a number of known factors that make people more susceptible to TB infection: worldwide the most important of these is HIV. Co-infection with HIV is a particular problem in Sub-Saharan Africa, due to the high incidence of HIV in these countries. Smoking and diabetes mellitus have also been identified as factors which increase susceptibility.
 
Nearly all countries in the world are now affected by the global resurgence of TB driven primarily by poverty and poor access to health services, migration and HIV. The WHO has adopted the goal of dramatically reducing the global burden of TB by 2015 in line with the Millennium Development Goals and the Stop TB Partnership targets and report that TB incidence and mortality rates have been falling since 2006 although there is still much work to be done [The Stop TB Strategy, WHO http://www.who.int/tb/strategy/stop_tb_strategy/en/index.html]. 
 
In the UK as a whole, the incidence of tuberculosis has increased steadily over the past two decades. The latest Public Health England annual TB report shows that rates of tuberculosis (TB) have stabilised in the UK over the past seven years, following the increase in the incidence from 1990 to 2005. However, despite considerable efforts to improve TB prevention, treatment and control, the incidence of TB in the UK remains high compared to most other Western European countries, with 8,751 cases reported in 2012, an incidence of 13.9 per 100,000 population.
 
The majority of TB cases occurred in large urban centres, amongst young adults, those from countries with high TB burdens, and those with social risk factors for TB. As in previous years, London accounted for the highest proportion of cases in the UK (39%) followed by the West Midlands PHE Centre area (12%).

Similarly to 2011, 73% of TB cases were born outside the UK and mainly originated from South Asia (60%) and sub-Saharan Africa (22%). The rate of TB among the non UK-born population was almost 20 times the rate in the UK-born, at 80 per 100,000 but has continued to decline over the last seven years. In the UK-born population, the incidence of TB has not declined in the past decade, with rates remaining stable at 4.1/100,000 per year. Within this population, those most at risk remain individuals from ethnic minority groups, those with social risk factors and the elderly.

In 2012, the annual number of tuberculosis cases in residents of Wales increased by 5% to 136 but rates remain low relative to other parts of the UK. In 2012, Wales reported the lowest rate of tuberculosis in the UK (4.4 per 100,000 cases). Consistent with the rest of the UK, the majority of cases in Wales were reported from urban areas, with over 50% of cases born outside the UK, originating from high tuberculosis burden countries.
 
 

Immunisation against TB


The BCG (Bacille Calmette Guérin) vaccine protects against TB (tuberculosis). It is made from a weakened strain of Mycobacterium bovis, the organism that causes TB in cattle. This organism has been modified in the vaccine so that it produces immunity against TB without causing the disease.  It is a live vaccine – that is, the bacteria in the vaccine are still alive but are weakened so that they do not cause TB disease.
 
Studies in the UK have shown the vaccine gives substantial (about 70-80%) though not complete, protection against developing active TB. Overall, BCG vaccination plays a limited role in TB control.
 
BCG was introduced in 1953 when the highest rates of tuberculosis were in older teenagers and young adults. It was given in schools with the aim of protecting young people before they left school. 
 
However, as the pattern of who gets TB is now different, the Joint Committee on Vaccination and Immunisation (JCVI), which advises UK Governments on immunisation policy, advised the programme should focus on people at higher risk of exposure to TB. In the UK the disease is now found mostly in people who have previously lived in, or have close links to, countries with high rates of TB.
 
The schools' programme nationally has been replaced with a programme of targeted vaccination for those individuals who are at greatest risk.
  
The new programme identifies and vaccinates babies and older people who are most likely to catch the disease, especially in those living in areas with a high rate of TB or whose parents or grandparents were born in a country where TB is common (i.e. 40 or more cases in 100,000 of the population per year).
 
More information about the composition of vaccines including the BCG vaccine is included in the Public Health England 'Immunisation Against Infectious Diseases' policy and guidance handbook (The 'Green Book') for health professionals which is available from the gov.uk website at: https://www.gov.uk/government/organisations/public-health-england/series/immunisation-against-infectious-disease-the-green-book
 
 

Surveillance of tuberculosis drug resistance


The United Kingdom Mycobacterial Surveillance Network (MycobNet) was established in 1994 to monitor tuberculosis drug resistance in the UK. Information on all cases of tuberculosis confirmed by culture at specialist mycobacterial reference laboratories is collated at HPA Centre for Infections, London. Information includes species (M. tuberculosis, M. bovis or M. africanum), drug sensitivity results and some demographic and clinical data. This information is used to monitor trends in drug resistance in tuberculosis, and is the basis of surveillance of M. bovis disease in humans.
 
Seven reference laboratories from the UK participate in this surveillance scheme, one of which is the Wales Centre for Mycobacteria (WCM) in Cardiff.
 
 

Requests for further surveillance data


If further surveillance data for tuberculosis in Wales are required, it may be possible to provide it on special request. Please use the surveillance data request form provided from this link.
 
 


Last updated: 23/01/2014