The Continual Challenge of Emerging Infectious Diseases
Emerging infectious diseases, which have shaped the course of humanity
and caused incalculable suffering and death, will continue to confront
society in unpredictable ways as long as humans and microbes co-exist,
write authors from the National Institute of Allergy and Infectious
Diseases (NIAID) of the National Institutes of Health in a review
article published in the July 8 issue of the journal Nature.
"The global scientific and public health communities must confront
with vision and sustained commitment to meet a
perpetual challenge," write David M. Morens, M.D, Gregory K.
Folkers, M.S., M.P.H., and NIAID Director Anthony S. Fauci, M.D.
"Broadly based prevention strategies, as well as new and improved
countermeasures, including surveillance tools, diagnostics, therapeutics
and vaccines, must continually be tested, refined and upgraded,"
says Dr. Fauci. "This will require a strengthened relationship
between public health and basic and clinical science."
In their paper, the authors classify three types of emerging infections
and consider methods for their control: newly emerging infections
(e.g. HIV, SARS); re-emerging/resurging infections (e.g. influenza,
West Nile virus); and deliberately emerging infections (e.g. microbes
used for bioterror).
The authors note that emerging infectious diseases are superimposed
on a constant backdrop of established infections. Approximately
15 million deaths in 2002 were directly attributable to infections,
according to the World Health Organization. Tragically, the authors
point out, the burden of all infections falls most heavily on those
least able to manage them: people living in developing countries,
especially infants and children, and indigenous and disadvantaged
minorities in developed countries.
Why do infectious diseases emerge and re-emerge? The viruses, bacteria
and parasites that cause these diseases continually and sometimes
dramatically change over time. The authors note that emergence results
dynamic interactions between rapidly evolving infectious
agents and changes in the environment and in host behavior that
provide such agents with favorable new ecological niches."
As a result, new pathogens arise, and familiar ones re-emerge with
new properties or in unfamiliar settings.
Historically, the authors write, the results have been devastating.
For example, importation of smallpox into Central America caused
10-15 million deaths in 1520-1521, effectively ending Aztec civilization.
AIDS, first recognized in 1981, now threatens to surpass in global
fatality the "Black Death" of the 14th century and the
influenza pandemic of 1918-1919, two notable infections that emerged
to each kill tens of millions of people.
In the past five years alone, two pathogens well known to countries
on other continents were seen in the Unites States for the first
time West Nile virus and monkeypox virus. In addition, a new infectious
disease, SARS, emerged in 2003 and has since caused more than 8,000
cases of illness and nearly 800 deaths around the world. In addition,
in 2001 the United States was confronted with a third, extremely
disquieting category of threat: a disease resulting from the deliberate
release of an infectious agent, anthrax, by a terrorist(s).
The authors write that an effective response to any new infectious
disease threat, whether it emerges, re-emerges, or is deliberately
introduced, involves mobilizing many different types of public health
activities. In particular, frontline surveillance and response is
critical and depends on rapid detection, clinical diagnosis and
containment. Concomitantly, basic and applied research enables the
development of medical countermeasures such as surveillance tools,
diagnostic tests, vaccines and therapeutics. The authors note that
these efforts have been accelerated by advances in fields such as
genomics/proteomics, nanotechnology, direct and computational structural
determination, immunology, and geographical information systems
and satellite imaging.
NIAID is a component of the National Institutes of Health, an
agency of the U.S. Department of Health and Human Services. NIAID
supports basic and applied research to prevent, diagnose and treat
infectious diseases such as HIV/AIDS and other sexually transmitted
infections, influenza, tuberculosis, malaria and illness from potential
agents of bioterrorism. NIAID also supports research on transplantation
and immune-related illnesses, including autoimmune disorders, asthma
and allergies. Press releases, fact sheets and other NIAID-related
materials are available on the NIAID Web site at http://www.niaid.nih.gov.
Reference: DM Morens, GK Folkers and AS Fauci. The challenge of
emerging and re-emerging infectious diseases. Nature 430: July 8,