TUBERCULOSIS

Prevention of new infections of Mycobacterium tuberculosis
and their progression to TB disease is critical to reduce
the burden of disease and death caused by TB, and to
achieve the End TB Strategy targets set for 2030 and 2035.
The targets of an 80% reduction in TB incidence by 2030
and a 90% reduction by 2035, compared with 2015, require
an historically unprecedented acceleration in the rate
at which TB incidence falls after 2025 (Chapter 2). This can
only happen if the probability of progression from latent TB
infection (LTBI) to active TB disease among the 2–3 billion
people already infected worldwide is reduced below the
current lifetime risk of 5–15%. 1 In some low-burden countries,
reactivation accounts for about 80% of new cases of
disease. 2,3 Interventions that could result in a much greater
reduction include more effective treatments for LTBI and a
new vaccine capable of preventing reactivation of LTBI in
adults.
There are three major categories of health interventions
currently available for TB prevention:
■ treatment of LTBI – through isoniazid daily for 6 or
9 months, or isoniazid plus rifampicin daily for 3–4
months, or rifampicin daily for 3–4 months or isoniazid
plus rifapentine once a week for 3 months – with particular
attention to children aged under 5 years who are
household contacts of TB cases with bacteriologically
confirmed pulmonary disease, and people living with
HIV (Section 5.1);
■ prevention of transmission of Mycobacterium tuberculosis
through infection control (Section 5.2); and
■ vaccination of children with the Bacille-Calmette-Guérin
(BCG) vaccine (Section 5.3).
The three main sections of this chapter present and discuss
the status of progress in provision of these services. Particular
attention is given to countries in the lists of 30 high
TB burden and 30 high TB/HIV burden countries (Chapter
2).
5.1 Treatment of latent TB infection
LTBI is defined as a state of persistent immune response
to Mycobacterium tuberculosis without clinically-manifested
evidence of active TB disease. There are two particular risk
groups for whom specific efforts to diagnose and treat LTBI
are recommended by WHO: children aged under 5 years
who are household contacts of pulmonary TB cases, and
people living with HIV. 4 Coverage of contact investigation
1
Vynnycky E, Fine PE. Lifetime risks, incubation period, and serial
interval of tuberculosis. Am J Epidemiol. 2000;152(3):247–263.
2
Heldal E, Docker H, Caugant DA, Tverdal A. Pulmonary tuberculosis in
Norwegian patients. The role of reactivation, re-infection and primary
infection assessed by previous mass screening data and restriction
fragment length polymorphism analysis. Int J Tuberc Lung Dis.
2000;4(4):300–307.
3
Shea KM, Kammerer JS, Winston CA, Navin TR, Horsburgh CR.
Estimated rate of reactivation of latent tuberculosis infection in the
United States, overall and by population subgroup. Am J Epidemiol.
2014;179(2):216–225.
4
World Health Organization. Guidelines on the management of latent
tuberculosis infection. Geneva: WHO; 2015 (http://www.who.int/tb/
publications/ltbi_document_page/en/, accessed 30 August 2016).
and treatment of LTBI among child contacts and people living
with HIV are in the top-10 list of indicators for monitoring
implementation of the End TB Strategy, with a target of
over 90% coverage by 2025 at the latest (Chapter 2, Table
2.1).
Data on provision of TB preventive treatment for people
living with HIV have been collected for more than 10 years.
However, until 2016 there was no standardized global guidance
on how to monitor the coverage of preventive treatment
among child contacts or other high-risk groups. Such
guidance has now been developed by a WHO Global LTBI
Task Force, 5 and the recommended indicators are shown in
Table 5.1. The rest of this section discusses findings from
data gathered from countries and territories in WHO’s
2016 round of global TB data collection about TB preventive
treatment for the three risk groups.
5.1.1 Child contacts under 5 years of age who are
household contacts of TB cases
In 2015, of the 189 countries that reported at least one notified
bacteriologically confirmed pulmonary TB case, 88
(47%) reported data about the number of contacts aged
under 5 years who were started on TB preventive treatment
(Fig. 5.1). A total of 87 236 child household contacts
were initiated on TB preventive treatment (Table 5.2), with
the largest numbers reported by the WHO African Region
(28% of the global total) and Eastern Mediterranean Region
(20% of the global total). At country level, Afghanistan reported
the largest number (10 164) followed by Bangladesh
(9833). Only nine of the 30 high TB burden countries reported
data. A few countries in the WHO European Region
noted that it was not possible to report data for children
specifically because preventive treatment is provided to
adults as well as children; this may also apply to some low
TB burden countries that did not report data. Thus, the data
reported to WHO understate the actual number of children
who were started on TB preventive treatment.
Comparisons of the number of children started on treatment
for LTBI in 2015 with national estimates of the number
of children aged under 5 years who were contacts of
bacteriologically confirmed pulmonary TB cases and eligible
for TB preventive treatment are also shown in Table
5.2. Globally, the 87 236 children started on TB preventive
treatment in 2015 represented 7.1% (range, 6.9–7.4%) of
the 1.2 million (range, 1.18 million to 1.26 million) children
estimated to be eligible for it. Higher levels of coverage
were achieved in the WHO Region of the Americas (best
estimate 67%; range, 63–71%) followed by the European
Region (best estimate 42%; range, 40–44%). In the high
TB or TB/HIV burden countries that reported data, coverage
ranged from 2.6% in Cameroon to 41% in Malawi.
5.1.2 People living with HIV
There has been a considerable increase in the provision
of preventive TB treatment in recent years, especially in
5
http://www.who.int/tb/challenges/task_force/en/
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