the health sector, with those who recognize the
importance of broader social drivers and impact of
infectious disease struggling to mobilize other sectors. For example, despite the long-acknowledged
association between poverty and tuberculosis
(TB) (7), combined health and social intervention
remains a rarity, and is only now being pioneered
in countries such as South Africa, where TB has
embedded itself as the largest killer. Financing
may stabilize or diminish, in part because other
disease areas or the health system are recuperating from any temporary loss of funding caused
by the epidemic (2). Resourcing the response becomes increasingly based on known risks and
benefits that can be more clearly compared with
alternative investments in the health sector or
beyond, articulated in “investment cases” for specific diseases (8). Health insurance organizations,
which at this stage are able to predict risk, may
start to cover any response in their insurance
benefits (and premiums). The disease itself takes
on an “identity,” and interest groups form out of
the populations where the disease is becoming
endemic, often advocating for attention and action. The disease now must compete for attention
and resources with other endemic diseases, even
if the benefits of disease control still clearly outweigh the costs (8).
The private response
Individual responses to a disease drive the pub-
lic response. At a personal level, epidemics may
inspire panic largely because the risk of acqui-
sition of infection is impossible to gauge and
treatments are limited. As individuals act to avoid
(often highly unknown) risks, they are willing to
behave in ways that may have substantial social
and economic costs and consequences. People
may avoid work, take children out of school, and
flee or minimize travel (9). This reaction and its
consequential costs are often not borne evenly
across populations. The ability of an individual
to act is constrained by economic and social
circumstances, and thus, even at an early stage,
epidemics start to impact different groups in
society differentially, as has been documented for
the Ebola virus epidemic in Liberia (10). Stigma-
tization of those perceived to be at greatest risk
of infection and transmission is common.
As epidemics transition into endemic disease,
people develop a perception that they understand
the risks of infection, giving them a sense of control. People cope with risk by adjusting behavior
and mitigating the consequences, often to the
point at which any new behaviors become a tolerated part of life. The move of the locus of responsibility from government to individual can then
be enabled by a belief that individuals can now
make informed choices, even when those individuals are highly constrained by their circumstances. For example, new forms of funding the
means of risk protection may emerge, such as the
social marketing of condoms or malaria bed nets,
ultimately sharing the financial burden of the
disease even among the very poor. As a disease
becomes endemic, governments generally still
provide some funding for treatment, but in the
context of resource scarcity, governments may fail
to fund universal access, leaving many to turn to
private care, even when treatment may prevent
others from being infected, such as in the case of
TB or HIV. For many interest groups, this is an
“underreaction” compared with the epidemic response. Even when the disease has settled into
populations, these groups may continue to sustain
the political imperative associated with epidemics
(11), calling for urgent action to end the disease,
unfortunately often with limited success.
The determinants of risk
The risk and perception of risk that drive the
individual and societal response to disease are a
combination of the probability of infection coupled
with the consequences of infection: The widespread
fear associated with epidemics is often driven by
the lack of effective treatment. In 2017, most of
us would prefer a diagnosis of HIV to one of Ebola
virus, but the distinction would have been less
clear prior to 1995, when fewer effective medi-
cines were available. Epidemic diseases typically
have higher mortality and morbidity than ende-
mic diseases, owing to lack of clinical experience
and knowledge, as well as innate pathogenicity.
Over time, effective prevention and treatment
interventions emerge. However, although im-
proved treatment is clearly a good thing, and
reduces the risk of catastrophic loss of individual
health, the reduction in risk may also provoke
a decline in political interest, initiating a more
endemic-style response. Where antimicrobial
resistance emerges, reducing the treatability of
endemic diseases such as TB, fear may return
and once again inspire a more epidemic-style
response.
Paradoxically, the amount of public funding
needed to respond to infectious diseases may increase during a transition from epidemic to endemic, as those organizations that made the
initial investments in medical technologies to
prevent, diagnose, and treat the disease attempt
to recoup their investment. The resource estimates for HIV were moderate initially but, as
effective treatment emerged, increased substantially (8). Likewise, the availability of more
effective treatment may increase costs to households, as the disease becomes chronic rather
than acute, leaving the households to deal with
the costs of long-term illness, and of accessing
care. For some population groups, unable to
afford the costs of accessing treatment (7), this
can worsen the endemic and entrenched nature
of the disease by reinforcing cycles between risk
and poverty, potentially exacerbating initial differentiation of risks that emerged in the epidemic
stage.
Lack of investment and political will allows
diseases to become entrenched in certain population groups, and the diseases then become very
expensive and difficult to control, eliminate, and
SCIENCE sciencemag.org 14 JULY 2017 • VOL 357 ISSUE 6347 157
In Maharashtra State, India, art students have painted murals across city walls to inform the general public about HIV/AIDS awareness and prevention.
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