Environmental Engineering Reference
In-Depth Information
Infectious Respiratory Diseases
Infectious diseases affecting the lungs and respiratory tract have special impli-
cations in public health. Bacteria and viruses responsible for these diseases are
transmitted between humans via droplets that are expelled from the nose or
mouth. Although direct transmission can occur (e.g., coughing or recirculated
air), droplets on nonporous surfaces (e.g., door knobs) can also be involved
in new infections. Environmental engineering can play a key role in ensuring
the safety and quality of air, particularly in the design of institutional air supply
systems, which have been implicated in the transmission of respiratory infections.
Control of transmission of respiratory dropletborne infections is achieved
through interventions at the individual level (protective masks, hand washing,
antibiotic treatment), the population level (restrictions on congregation and move-
ment), and environmental levels (air filtration, institutional design).
In this chapter we describe two respiratory infections and their control mecha-
nisms, of concern to developing and develop countries: tuberculosis and influenza.
Table 2.8 summarizes the major respiratory illnesses.
Tuberculosis
Tuberculosis (TB) is caused by
Mycobacterium tuberculosis
,
M. africanum
or
M. bovis
. Infection in the respiratory tract can lead to
pul-
monary tuberculosis
, resulting in calcified nodules in the lungs, trachea, and
bronchea. Infection with the mycobacterium at sites other than the lungs can
happen, although much less frequently. Only 5 to 10 percent of those infected
with TB will show clinical signs of disease or become infectious.
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In 2005, the
WHO estimates that there were 1.6 million deaths due to tuberculosis world-
wide, making it one of the most common causes of human mortality on the
planet.
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Two developments in the last decade and half have made the spread of
TB even more worrisome. First, the rapid increase in HIV infections has revealed
that those infected with HIV are at much higher risk of acquiring TB. Second,
the emergence of multiple-drug-resistant strains of tuberculosis (MDR-TB) have
resulted from improper use of antibiotics; these strains can no longer be treated
with the commonly available antibiotics and require expensive and intensive
medical care. In addition, extremely drug resistant tuberculosis (XDR-TB) has
also been reported, which is difficult to cure even with the most advanced forms
of antibiotics available.
The World Health Organization has a large-scale program called Stop TB.
These programs has the following six components
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:
1.
Pursue high-quality DOTS expansion and enhancement
. The standard of
care for tuberculosis is daily dosing of antibiotics that is observed by a
health care worker. Direct observed therapy, short course (DOTS) was
created in response to the realization that many TB patients were not com-
pleting the prescribed course of antibiotics, due to the number and size
of the tablets that must be swallowed daily and the duration of therapy,
which can be months to a year. Patients may not show outward signs of
