Environmental Engineering Reference
In-Depth Information
fulminate infection (or convalescence), there are overt physical manifestations of
disease pathology. Clinical diagnosis based on symptoms can occur at this phase.
∗
Individuals may cycle through periods of clinically expressed disease and carrier
state. This cycling can last days, weeks, months or even decades (e.g., herpes,
chicken pox/shingles, tuberculosis), depending on the disease. In the fourth phase,
remission (or post-convalescence), the individual will no longer express the signs
of the disease, and is immune to reinfection. Immunity to reinfection is mediated
by circulating antibodies, special protein-based complexes that can “remember”
the identity of pathogens and serve to immediately neutralize (render harmless)
an infectious organism when it reenters the body. However, in some cases, immu-
nity can wane with age, and the individual may become susceptible to infection
by the same organism again. The importance of understanding these four phases
will become clear as interventions targeting all phases are discussed.
Behavioral Change
Behavioral interventions aim to control the actions of the individual. The most
drastic of these measures, in a civil liberty-oriented society, is restriction of
association, achieved through isolation of infected individuals showing signs of
disease, quarantine of suspected carriers, and cancellation of school or mass
gatherings. The basic idea is to limit the number of individuals who are exposed
to the carrier or diseased persons. In order to sustain an infection in a population, a
certain number of new individuals must be infected in a given time period. These
numbers can be calculated and form the basis for ascertaining the length of the
restriction period. Most countries have strict laws on isolation and quarantine, and
these are some of the most powerful tools wielded by public health authorities.
However, due to the severe interruption of lifestyle and livelihood resulting from
these measures, they are rarely used. There has been a shift recently to develop
protocols for more benign methods of limiting association, following a “snow
day” model. In these instances, people would be encouraged (not forced) to stay
home for a few days to prevent new infections.
Other forms of behavior modification for the prevention of infectious disease
transmission are routinely employed. For example, in hospitals, frequent hand
washing by health care professionals prevents the transmission of disease between
patients.
18
Seatbelts, speed limits, driving age restrictions, and drunk driving
∗
For some infections, such as HIV, there may be an acute phase where mild symptoms are apparent,
before progression into the carrier state. For HIV, this acute phase manifests as flulike symptoms
and occurs in the week or two following infection. Not all individuals will experience this phase.
After this acute phase, all outward signs of the disease subside and the person enters the carrier
stage, during which he or she can be infectious (depending on the amount of circulating virus and
integrity of the immune system). The acute phase infection has been used as an early surveillance
system to identify those recently infected, weeks before traditional testing would have been able to
detect the presence of the infection. It is hoped that early detection during the acute phase could be
exploited to treat patients before the virus enters particular cell types, increasing the likelihood of
clearing the infection.
