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Despite important advances in its
treatment over the past two decades, tuberculosis remains a major
infectious disease. Approximately one third of the world’s
population harbors Mycobacterium tuberculosis and
is at risk for developing disease in the near or distant future.
The incidence and prevalence of tuberculosis increased over the
past 15 years partly due to the human immunodeficiency virus (HIV)
epidemic and the prevalence of drug-resistant tuberculosis. The
failure to control tuberculosis in both developed and developing
countries represents one of our greatest public health failures.
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Two elements determine a child’s risk for developing
tuberculosis disease.1 The first is the likelihood
of exposure to an individual with infectious tuberculosis, which
is primarily determined by the individual’s environment.
The second is the ability of the person’s immune system
to control the initial infection and keep it clinically dormant.
Without treatment, disease develops in 5% to 10% of
immunologically normal adults with tuberculosis infection. In young
children, the risk is greater; as many as 40% of those
younger than 1 year with untreated tuberculosis infection develop
radiographic or clinical evidence of tuberculosis disease. Methods
of preventing disease in infected individuals benefit children and
adolescents even more than adults.
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About 60% of cases of childhood tuberculosis occur in
infants and children younger than 5 years.2 The
ages of 5 to 14 years are often called the “favored age” because
children in this range may become infected, but usually have the
lowest rate of tuberculosis disease. The gender ratio for tuberculosis
in children is about 1:1 in contrast to adults, in whom males predominate.
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Children acquire M tuberculosis from adults in
their environment. Environmental risk factors include those characteristics
that make it more likely that the child shares the air with an adult
with infectious tuberculosis. Factors that increase the risk of
a child being infected with M tuberculosis include
(1) birth or travel/residence in a country in which tuberculosis
is endemic; (2) early childhood environments with exposures to multiple
high-risk caregivers, for example, some orphanages; or (3) contact
with high-risk adults who have had previous residence in a jail,
prison, or high-risk nursing home, and homelessness in some communities. Also
included are use of illegal drugs, experience as a health care worker
who cares for high-risk patients, or locally defined risk factors. Factors that
increase the risk of developing disease once infected include age
younger than 2 years, coinfection with HIV, other immunocompromising diseases
or treatments (corticosteroids, tumor necrosis factor-alpha inhibitors),
and malnutrition.3
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Most children in the United States are infected with M
tuberculosis in the home, but outbreaks of childhood tuberculosis
centered in elementary and high schools, nursery schools, family
daycare homes, churches, school buses, and stores have occurred.4 Childhood
tuberculosis case rates in the United States and in other developed
countries are strikingly higher among ethnic and racial minority
groups and among the poor. In the United ...