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Introduction &
Global Distribution
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Plague is a bacterial
zoonosis that causes high mortality (>50%) in untreated cases and has
epidemic potential. It is best known as the cause of Justinian's Plague
(middle 6th century) and the Black Death (middle 14th
century), two devastating pandemics that killed millions and altered the
course of history. A third lesser-known pandemic, began in China in the
late 1800s, and spread to all inhabited continents, causing nearly 30
million cases and over 12 million deaths in the period 1896-1930. The
Third, or Modern Pandemic prompted an intensive multinational research
effort that resulted in the identification of the causative agent of plague
(Yersinia pestis, a gram-negative bacterium) and conclusive evidence
that rat fleas transmit the disease to humans during epidemics. Later
studies indicated that smaller numbers of cases also arise as a result
of persons being bitten by wild rodent fleas, handling infected animals,
or inhaling infectious respiratory droplets coughed by persons with plague
pneumonia. Others demonstrated that plague bacteria are maintained in
nature through transmission cycles involving wild rodent hosts and flea
vectors. Armed with this knowledge, public health workers were able to
design and implement prevention measures that reduced the incidence and
spread of plague in many regions. The effectiveness of these prevention
programs was further enhanced in the mid-20th century by the development
of improved and rapid diagnostics, effective antibiotics, vaccines, insecticides
and rodenticides.
Despite the scientific
advances described above, and the success of some prevention efforts,
plague remains a threat in many areas of the world where enzootic foci
continue to exist. Outbreaks of hundreds of cases still occur in some
countries of Asia, Africa and South America, especially in those regions
where persistent foci are situated near human populations living in unsanitary,
rat-infested environments (click for
link to WHO Weekly Epidemiological Record). In some instances plague
outbreaks in developing countries have spread to urban areas, including
port cities, which increases the risk of large epidemics and further spread
of the disease. In these and other situations changing demographics, behaviors
and environmental conditions in he developing world create conditions
conducive to increasing numbers of sporadic cases and to the possible
geographic spread of plague. Many countries, including the United States,
are unlikely to have rat-associated outbreaks, but continue to experience
sporadic cases as a result of persons being bitten by infected wild rodent
fleas or handling infected animals. Other serious concerns include the
recent identification of multidrug resistant Yersinia pestis in
Madagascar and the threat that plague might be used as an agent of biowarfare
or bioterrorism.
Reducing the risk
of human plague depends on the implementation of effective prevention
programs that include capabilities for the surveillance, control, and
diagnosis of the disease. Appropriate education programs for the general
public and health care workers are also critical. The WHOCC-Plague at
the Division of Vector-Borne Infectious Diseases actively works with other
public health agencies to develop cost-effective plague prevention programs,
respond to plague outbreaks, and monitor the status of plague around the
world.
The specific mission
goals of the WHOCC-Plague are to:
- Provide epidemiologic
assistance, including participation in on-site investigations and the
planning and execution of epidemic control measures.
- Consult and collaborate
on plague programs and the development of strategies for the prevention
of human plague.
- Provide laboratory
diagnostic support in epidemic situations, including the confirmation
and characterization of Yersinia pestis isolates.
- Maintain a Yersinia
pestis reference collection for use by the scientific and medical
community.
- Provide special
diagnostic reagents through WHO or PAHO to other diagnostic laboratories.
- Provide training
in-country or at DVBID on laboratory diagnosis, surveillance systems,
field techniques, and epidemiology.
- Perform cooperative
field and laboratory research on the epidemiology, ecology, control,
and diagnosis of plague.
The activities of
the WHOCC-Plague are conducted within the Bacterial Zoonoses Branch (BZB),
which is under the direction of Joseph Piesman, Ph.D. The Center's activities
are performed through the cooperative efforts of the BZB's Plague Section,
Diagnostic and Reference Section, and Epidemiology Section, which have
expertise in plague surveillance and control, (Plague Section - Chief,
Kenneth Gage, Ph.D.), bacteriology, serology and molecular biology (Diagnostic
and Reference Section - Chief, May Chu, Ph.D.), and epidemiology and treatment
(Epidemiology Section - Chief, Paul Mead, M.D.).
The WHOCC-Plague
is capable of providing:
- Comprehensive
and integrated responses during emergency investigations of human plague
in the United States and other countries.
- On-site evaluations
of plague surveillance, diagnosis, prevention and control programs in
the United States and other countries.
- Diagnostic and
reference services during outbreaks, routine surveillance activities,
or research projects.
- Training at the
WHOCC-Plague or through on-site workshops held elsewhere in the United
States or in other countries.
- Training materials,
manuals and scientific information produced by WHOCC-Plague staff, including
sections on surveillance, clinical diagnosis and treatment in WHO's
recently revised Plague Manual, a separate WHO-and CDC-sponsored manual
on laboratory diagnosis of plague, and numerous book chapters, articles,
pamphlets on plague (See Publications section).
- Sponsorship of
international plague workshops, such as those held at the Emerging Infectious
Diseases meetings held in Atlanta, Georgia, USA in 1998 and 2000.
The WHOCC-Plague
will continue to improve and expand its capabilities as a center of excellence
on plague prevention. It will support a global plague network to strengthen
surveillance, outbreak response and integrated programs of control. Specifically,
the Center plans to:
- Emphasize the
development and implementation of effective, sustainable plague prevention
programs in the United States and other countries.
- Continue to develop
its core of subject matter experts who can provide consultation and
training on all aspects of plague surveillance, prevention, control
and diagnosis.
- Improve its ability
to rapidly respond with onsite assistance during threatening plague
epidemics or other situations.
- Evaluate treatment
and patient management strategies.
- Provide enhanced,
rapid reference diagnostic services.
- Expand its molecular
epidemiology capabilities.
- Provide entomological
expertise on plague vectors and their role in disease transmission to
humans.
- Increase the
capacity for GIS and remote sensing studies of the landscape ecology
and epidemiology of plague.
- Improve its abilities
to use GIS and remote sensing as tools for surveillance and estimating
human plague risk.
- Increase the
capacities of other plague programs through training programs at the
WHOCC or through onsite training workshops.
- Improve its ability
to respond to possible bioterrorism events.
- Pursue an active
research program intended to develop improved methodologies for plague
surveillance, prevention, control, and diagnosis.
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