Tuberculosis

Background

Tuberculosis (TB) is a disease caused by:

  • Mycobacterium tuberculosis
  • M. bovis
  • M. africanum
  • M. canetti
  • M. microti

Together they form the Mycobacterium tuberculosis complex.

There are two forms of TB. The first affects the lungs and the other causes infection elsewhere in the body. The symptoms that occur when TB disease develops aren't usually very specific but often there are complaints of:

  • tiredness
  • listlessness
  • loss of weight
  • night sweating

When TB affects the lungs, a cough is usually present for weeks or even months.

TB is a notifiable disease under the Public Health etc. (Scotland) Act 2008. More information on the Public Health etc. (Scotland) Act 2008 is available from the Scottish Government website.

The Scottish Mycobacteria Reference Laboratory (SMRL) undertakes the identification, including molecular characterisation, and susceptibility testing of all mycobacterial isolates in Scotland, both for clinical management and for epidemiological purposes. The laboratory reports all identification results weekly to our organisation through the Electronic Communication of Surveillance in Scotland (ECOSS).

Transmission

Transmission of TB is by inhalation of infected droplets and requires prolonged close contact, for example sharing sleeping quarters, with an infected individual. An important feature of TB is that after infection, the bacteria can remain latent in the body for a long time, possibly even lifelong, causing no symptoms. People with latent TB infection are not infectious. Under favourable conditions, the bacteria can start multiplying and cause clinical disease.

Guidance

The following guidance has been approved for use in Scotland by the Scottish Health Protection Network Guidance Group (SHPN-GG) and should be used in conjunction with the SHPN addendum:

Other guidance:

 

For all infection prevention and control guidance visit the A-Z ​pathogens section of the National Infection and Prevention Control Manual.

Data and surveillance

The establishment of the Enhanced Surveillance of Mycobacterial Infections (ESMI) scheme in 2000 represented a major development in the surveillance of TB in Scotland. Our organisation co-ordinates the scheme and incorporates the European minimum dataset and provides feedback to the various agencies involved in the diagnosis, treatment and control of TB.

Overall numbers, rates and geographical distribution

TB infographicA total of 288 cases of TB were reported to the ESMI in 2017, meaning an annual incidence of 5.3 cases per 100,000 population. This was a decrease of 7% in both the number of cases and annual incidence when compared with the 310 cases, 5.7 cases per 100,000 population in 2016. The infographic would go here. 

Figure 1, showing the numbers of tuberculosis ases and incidence in Scotland, 2000 to 2017.

Gender and age

In 2017, 59.4% of TB cases occurred in males, this was 171 cases, and 6.5 cases per 100,000 population. Males were more common in all age groups except those aged under 15 years and those aged over 85 years. Most TB cases occurred in those aged 25 to 34 years, that's 25% and 72 cases at 9.8 cases per 100,000. It was fewest in those aged five to 14 years with three cases, at 0.7% and 0.5 cases per 100,000 population.

Figure 2, showing the number of tuberculosis cases and rate per one hundred thousand population by age group, 2017.

Place of birth

Place of birth was known for 98.3% of cases in 2017. Of these, 56.9% were born outside of the UK. This is a decrease in the percentage of non-UK born cases when compared with the 62.2% in 2016 and 57.3% in 2015.

Figure 3, showing the number and proportion of tuberculosis cases reported to ESMI born outside the UK, 2000 to 2017.

In 2017, the rate of TB among those born outside the UK decreased further to 33.8 cases per 100,000 population from 41.4 cases per 100,000 per population in 2016. The rate of TB among those born in the UK increased slightly to 2.5 cases per 100,000 population in 2017 from 2.4 cases per 100,000 population in 2016. The rate of TB amongst non-UK born individuals was approximately 13.5 times higher than the rate in the UK born population at 33.8 cases versus 2.5 cases per 100,000 population. This is comparable to the previous year.

Figure 4, showing tuberculosis notification rates by place of birth, 2004 to 2017.

Risk factors

Information on risk factors was known for the majority of cases in 2017, that's 93.8% of cases. Risk factors were identified for 33.0% of cases, that's 89 cases, of whom nine cases and 3.3% had more than one known risk factor. Identified risk factors included:

  • being a refugee or asylum seeker, that's 40 cases and 14.8%
  • alcohol misuse, that's 20 cases and 7.4%
  • working in healthcare, that's 14 cases and 5.2%
  • immunosuppression, that's 13 cases and 4.8%
  • homelessness, that's seven cases and 2.6%
  • residency in a residential or corrective institution, that's four cases and 1.5%
  • drug misuse, that's two cases and 0.7%

Figure 5, showing the reported risk factors for tuberculosis, 2000 to 2017.

Drug resistance

The first line drugs considered for the treatment of TB in the UK are:

  • isoniazid
  • rifampicin
  • ethambutol
  • pyrazinamide

Of the 196 culture confirmed cases of TB reported in 2017, 191 had drug susceptibility tests for both isoniazid and rifampicin. Resistance to at least one first line drug at the start of treatment was reported for 21 cases, that's 11.0%. Further to that:

  • 15 cases, that's 7.9%, isolates were resistant to isoniazid
  • three cases, that's 1.6%, were resistant to rifampicin
  • two cases, that's 1.0%, were resistant to ethambutol
  • nine cases, that's 4.7%, were resistant to pyrazinamde

Three cases, that's 1.6%, were resistant to both isoniazid and rifampicin and therefore defined as multidrug-resistant TB (MDR-TB). Two cases were male and all were aged 25 to 34 years. Two cases presented with pulmonary disease, all were non-UK born and not known to have a previous diagnosis of TB. No TB cases reported in 2017 had extensively drug-resistant TB (XDR-TB).

Table 1, showing the number and proportion of tuberculosis cases with first line drug resistance reported to ESMI, 2000 to 2017.

TB outcomes in the drug sensitive cohort at 12 months

In 2016, 310 cases of TB were reported to ESMI of which one case was rifampicin resistant and was therefore excluded from outcomes analysis. Outcomes data were available for 87.4% cases, of whom 82.2% had successfully completed treatment at 12 months, which is slightly higher than that reported in 2015 when 79.0% of cases successfully completed their treatment.

Those most likely to complete their treatment are those:

  • with pulmonary disease
  • born outside of the UK
  • aged under 65 years
  • with no identified risk factor for TB
  • with no previous diagnosis of TB

Pulmonary disease

Relative risk (RR) 4.9, 95% confidence interval (CI) 2.1 to 11.5, p less than 0.0005

Where p is the level of marginal significance within a statistical hypothesis test representing the probability of the occurrence of a given event.

  • Born outside of the UK
    RR 3.2, 95% CI 1.6 to 6.3, p less than 0.005
  • Aged under 65 years
    RR 5.2, 95% CI 2.6 to 10.4, p less than 0.005
  • No identified risk factor for TB
    RR 2.1, 95% CI 1.1 to 4.1, p less than 0.05
  • No previous diagnosis of TB
    RR 2.3, 95% CI 1. to 4.1, p equal to 0.002

Figure 6, showing the proportion of tuberculosis cases with treatment outcomes information at 12 months, 2000 to 2016.

Vaccination

The Bacille Calmette Guérin (BCG) vaccine is offered to those babies who are more likely than the general population to come into contact with someone with TB. This is because they either lived in an area with high rates of TB, or their parents or grandparents came from a country with high rates of TB. These include some countries in Eastern Europe, as well as South-East Asia and sub-Saharan Africa.

The vaccine is usually offered soon after birth, either while the baby is still in hospital or soon after the patient returns home. However, it can be given at any time if necessary. The vaccine gives protection against severe forms of the disease, like TB meningitis and miliary TB, in children under five years of age. Further information can be found in the green book, chapter 32, on the Public Health England (PHE) website.


BCG vaccine for the national immunisation programme

Since 2015, deliveries of a UK licensed BCG vaccine from the Statens Serum Institut (SSI) in Denmark, were interrupted due to manufacturing issues and this vaccine was unavailable.

From June 2016, PHE secured an alternative BCG vaccine for use across the UK. InterVax BCG vaccine was then used for the national BCG immunisation programme. This was supplied as an unlicensed product, which meant it did not have a valid licence in the UK. The vaccine was provided in accordance with medicines legislation allowing an unlicensed medicine to be supplied when a licensed alternative was not available.

In August 2018, AJ Vaccines resumed supply of licensed BCG vaccine into the UK. There are no current restrictions on ordering quantities of the AJ Vaccines BCG vaccine for the national BCG programme.