Tuberculosis (TB) is caused by mainly Mycobacterium
transmitted through the airborne route
where the TBbacilli are suspended in aerosol droplets. It typically affects the
lungs (pulmonary TB) but can also affect
other sites (extra pulmonary TB)1.The major source of infection is a person suffering from active
pulmonary tuberculosis and transmission
can occur through coughing, sneezing, speaking or laughing 2.During coughing, sneezing and perhaps
talking, aerosol droplets of different sizes may be produced. Large droplets (> 20µm) fall straight to the
where as intermediate sized particles (5-20µm) fall at a slow rate or
remain temporarily suspended in air. Droplets less than 5 µm in
diameter remain suspended in air for longer periods of time.Thetubercule
bacilli are swiftly killed by ultraviolet rays (day light)therefore transmission
is predominantly indoors 3.Spreading
of TB is accompanied by several epidemiological factors, notably the HIV/AIDS
epidemic, low socio-economic status, overcrowding and malnutrition 4.
diagnostic methods are implementing in different years to increase detection
rate of the TB bacilli and effective treatment has been used to treat TB for
several decades, but TB remains a major global health problem and one of the
top 10 causes of death worldwide, ranking above HIV/AIDS as one of the leading
causes of death from an infectious disease. Therewere an estimated1.8 million
TB deaths and 10.4 million new (incident) TB casesin 20155.
Most of the
estimated number of cases in 2015 occurred in Asia (61%) and the WHO African
Region (26%).The 30 high TB burden countries accounted for 87% of all estimated
incident cases worldwide.About 84% of TB deaths among HIV-negative people
occurred in the WHO African Region and South-East Asia Region in 20156.
international targets for tuberculosis control, framed within the United
Nations’ Millennium Development Goals (MDGs), are to ensure that by 2015 the
global TB incidence rate is declining and the global TB prevalence and death
rates for 1990 are halved. These targets are to be achieved by implementing World
Health Organization (WHO’s) Stop TB Strategy.WHO estimates that the prevalence
and death rates have been falling longer and faster than the incidence rate.7.
Globally, the TB
mortality rate fell by 47% between 1990 and 2015. The target of a 50% reduction
was met in four WHO regions the Region of the Americas, the Eastern
Mediterranean Region, the South-East Asia Region and the Western Paci?c Region and
in 11 high TB burden countries.
prevalence fell by 42% between 1990 and 2015. The target of a 50% reduction was
achieved in three WHO regions – the Region of the Americas, the South-East Asia
Region and the Western Paci?c Region – and in nine high TB burden countries.
This target appears out of reach in the African, European and Eastern
Mediterranean regions8. HIV/AIDS,
Poverty, population growth, migration, diabetes, economic and social conditionscan
be attributed to fells the targets of 50% reductions prevalence in 20159.
incidence decline 1.4% per year from 2000 to 2015 and 1.5% from 2014 to 2015.
The fastest declines are in the WHO European Region (3.3% per year from 2014 to
2015). The estimated decline in the incidence rate since 2010 has exceeded 4%
per year in several high TB burden countries, like Zimbabwe (11%), Ethiopia
(6.7%), Namibia (6.2%) and Kenya (5.0%). Beside mortality rate (per 100 000 population) fell by 34%
between 2000 -2015 and by 2.7% between 2014 and 2015. Rates have also been
falling in all six of the WHO regions Since 2010, the fastest average rates of
decline in the mortality rate have been in the WHO Eastern Mediterranean and
European regions (6.5% and 6.2% per year, respectively) and slowest in the
WHO African Region (2.2% per year10.This needs to accelerate to
atarget of zero catastrophic costs for TBaffected families, a 4–5% annual decline incidence by 2020 to
reach the first milestones of the End TB Strategy and also to achieve 2030 targets of Sustainable
development goals (SDGs) which is 80% reduction in TB incidence and 90%death of
TBcompared with levels in 20155, 11, 12 .
In Ethiopia, TB has been
identified as one of the major public health problem, and the effort to control
TB strategy began in the early 1960s.11. However, these strategies were
not able to reduce the disease burden. As a result, a standardized and
well-organized TB programme, which is Directly Observed Treatment Short course
(DOTS) implemented since 1992 as a pilot study and since 1997, DOTS has been
scaled up to include the entire country12,13. By implementing this strategy Ethiopia
successfully achieved WHO’s 2015 TB targets14. The incidence rate dropped from
419 to 207 cases per 100,000 people from
1995-2014 and mortality to 33 deaths per
100,000 people. Despite a reduction in Ethiopia’s annual TB mortality rate from
94 to 33 deaths per100,000 from 2004-2014Ethiopia ranking the10th
among the world’s 22 high burden countries for TB and 4th in sub
Saharan Africa5,With close to 200,000 new cases
estimated each year.While TB kills an estimated
32,000 Ethiopians every year (more than 80 people per day) 10.
In addition, in 2015 WHO estimates case-detection rate was 40 percent gap which shows an estimated 80,000
individual develop TB each year 5.
Thisindicate; conduct a suitable program to achieve 2030 targets of SDGgoal
which is cut new cases by 80% and ensure
that no family is burdened with
catastrophic costs due to TB5,15.
To conduct a
suitable program, TB control activities require regular measurement of morbidity of the disease and improve understanding of
the epidemiology of TB in the target area 16. Assessment of the
epidemiological indices within a specific time period can also help planners to
focus on the main problems of a community and to assess the efficacy of
preventive programs 17. In addition, information is
required to monitor the progress toward sustainable development goal targets.
Currently, data regarding theprevalenceof TB and associated factors have been
released at different health facilities. However,there is no published such
data inTigray region since 2011. Besides, in Ethiopia, the socioeconomic,
lifestyle and environmental conditions differ across regions18. Moreover, there are no clear trends
in smear positive pulmonary TBprevalence in different parts of the country
specifically in Tigray region. Given the reasons provided, the aim of present
study will be assessed trends insmear-positive TB prevalenceand its associated
factors during 2013-2017 in Tigray regional state.The current study will help
to assess the progress toward SDG targets and design appropriate preventing and
control strategies. In addition; the study will also provide baseline
information for further related studies.