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 PDF Version
WHO/WPRO/SEARO Meeting on
DengueNet Implementation in South-East Asia
and the
Western Pacific, Kuala
Lumpur, 11-13 December 2003
Weekly Epidemiological Record,
2004, 79(6): 57-62
Dengue/DHF – Global public
health problem
Epidemic dengue fever and dengue haemorrhagic fever (DHF) have emerged
as a global public health problem in recent decades, with the development of
hyperendemicity in urban and peri-urban centres of many tropical and
subtropical countries. Asia-Pacific countries have more than 70 % of the
disease burden; in several of them, DHF has become a leading cause of
hospitalization and death among children. Latin America and the Caribbean appear to be following the same DHF
epidemic trend, with the disease affecting all ages and case-fatality rates
as high as 10-15 % in areas with limited health service infrastructure. The
African and Eastern
Mediterranean
regions are much less affected. Air travel is also facilitating the rapid
global movement of dengue viruses and increasing the risk of DHF epidemics
through the introduction of new serotypes. Globally, 2.5 billion people live
in areas where dengue viruses can be transmitted: an estimated 50 million
dengue infections occur each year, with 500,000 cases of DHF and at least
22,000 deaths, mainly among children. Although dengue is a notifiable disease
in many endemic countries, only a small proportion of cases are reported to WHO.
Rationale for DengueNet
DengueNet, WHO’s global surveillance system
for dengue fever and DHF, has been created as a web-based central data
management system to collect and analyse standardized epidemiological and
virological data in a timely manner and to present epidemiological trends as
soon as new data are entered. Strengthening epidemiological and virological
surveillance of dengue and DHF, including implementation of DengueNet, for
early detection, planning and response is one of the four main priorities of WHO’s global prevention and control strategy, adopted in
resolution WHA55.17 in May 2002. DengueNet, when fully implemented, will facilitate
WHO’s global outbreak and response activities and support the GOARN .
Epidemiological and laboratory-based surveillance is required to
monitor and guide dengue/DHF prevention and control programmes whether these
are based on vector control or possible future vaccination with a safe,
effective and affordable vaccine. Recent and encouraging research
developments have made it likely that a dengue vaccine will become available.
As a consequence, the public health community needs to define the burden of
dengue for society, so that adequate cost-benefit analyses can be presented
to government leaders before they decide to use the vaccine. Standardized
global dengue surveillance data, one of the principal results expected from
the establishment of DengueNet, have become critical.
Phased implementation of DengueNet
First meeting in San Juan,
Puerto Rico,
July 2002
The first DengueNet meeting was held jointly with WHO/PAHO and the WHO
collaborating centre for dengue/DHF at the Centers for Disease Control and
Prevention (CDC Dengue branch; San Juan, Puerto Rico).
Its objective was to describe and demonstrate DengueNet to prospective users
and to launch a pilot, building on the existing reporting systems and network
of dengue laboratories in the Americas. Epidemiologists and virologists from
eight countries in the Americas, three countries in Asia and five WHO collaborating centres
provided recommendations for the administrative and technical procedures
involved in making DengueNet operational.
Second meeting in Kuala Lumpur,
Malaysia, December 2003
After pilot use of DengueNet by four MemberStates and one network representing 20 island
countries in the Americas, and after changes to the supporting
computer hardware, software, and routines, a second meeting was convened
jointly with WHO/WPRO/SEARO and the WHO collaborating centre for dengue/DHF
at the University of Malaya in Kuala Lumpur, 11-13 December 2003. The objective was to
expand the pilot to South-East
Asia and the
Western Pacific, building on the lessons learned from the pilot conducted in
the Americas. About 70 participants included national
epidemiologists, laboratory specialists, and clinicians from 19 Asia-Pacific
countries, three countries in the Americas, six WHO collaborating centres, and WHO
HQ, regional and country staff .
The plenary presentations and discussions focused on: (1) the
challenges and need for standardized global epidemiological and laboratory
surveillance of dengue and DHF; (2) the activities of the Pediatric Dengue
Vaccine Initiative (PDVI); (3) the national surveillance and reporting
systems in the participating countries in South-East Asia and the Western
Pacific; (4) the activities of the participating WHO collaborating centres;
(5) the WHO global strategy and regional programmes; (6) WHO’s global
outbreak and response activities and GOARN; (7) the DengueNet pilot and
lessons learned; (8) presentation of DengueNet and a “hands on” session with
the “new” prototype web site in Global Atlas.
Two working groups were convened. The first reviewed and defined the
epidemiological data and reporting requirements for DengueNet, modifications
needed to the present format, identification of countries for expanding the
DengueNet pilot to Asia-Pacific regions, and roles and responsibilities of
national and international partners. A subgroup also reviewed and defined the
objectives of DengueNet. The second working group reviewed the existing
laboratory capacity in South-East Asian and Western Pacific countries in
relation to DengueNet, identifying the current needs (and gaps) for
laboratory standards, quality control, and dengue serological diagnosis and
virus isolation, as well as for reporting and information exchange. The group
made recommendations that focused on strengthening regional dengue laboratory
diagnosis capacity, so that laboratories participating in DengueNet are able
to report data of the highest quality possible within their working
environment.
Meeting outcomes
Objectives of DengueNet
The participants agreed that the overall objective of DengueNet is to
improve capacity for effective national and international planning for the
prevention and control of dengue and that the specific objectives for
implementing this global surveillance system are:
 to provide early warning of potential
outbreaks of dengue disease or of the introduction of dengue viruses into
epidemiologically silent areas, for the purpose of implementing timely
control measures and notifying decision-makers in institutions whose
occupations or livelihood may be affected;
to strengthen and standardize epidemiological
surveillance of DF and DHF;
to promote the use of standardized clinical
case definitions and reporting criteria for dengue illnesses, permitting
comparisons between countries and over time;
to strengthen the network of collaborating
centres and national laboratories for serotype determination and strain
characterization;
to promote improvement in the quality of
laboratory data reported at national and international levels;
to provide a standardized database for
epidemiological research and analysis;
to provide data useful for estimating the
burden of disease (including the social and economic burden) on a national,
regional, or global scale;
to support the improvement in national and
international alert and response capacity for dengue/DHF outbreaks; and
to promote the free
and timely exchange of epidemiological information between affected
countries, their neighbours, and other stakeholders in order to facilitate
and promote dengue control activities within the region.
Recommendations of the laboratory working
group
To strengthen the regional dengue laboratory
diagnosis capacity, the participants of this group made the following
recommendations for national laboratories, WHO collaborating centres, WHO,
and government health authorities.
Quality control
Quality control/proficiency testing should be
undertaken by the national laboratory/WHO collaborating centre for other
laboratories in the country concerned.
A reference centre should be established at
the WHO Collaborating Centre for Tropical Viral Diseases, Nagasaki,
Japan, to undertake
coordination of quality assurance/ control for other WHO collaborating
centers and designated national laboratories in the two Regions.
The Nagasaki
reference centre should coordinate, organize, and distribute a WHO panel of
reference sera for validation of tests/kits/rapid tests by WHO, national
laboratories, and WHO collaborating centres.
Reference services
Countries that do not have facilities for
virus isolation should send appropriate samples to a WHO collaborating centre
of their choice after consultation with that centre.
WHO should recommend capacity-building for
virus isolation to the ministries of health of countries that lack
facilities.
In collaboration with WHO country and regional
offices, WHO collaborating centres should provide reference reagents to
national laboratories – standard inactivated antigens, monoclonal antibodies,
standard sera, cell lines for virus isolation, and prototype dengue virus
strains.
Laboratory training
WHO should organize regional training courses
on laboratory diagnosis of dengue and other flaviviruses.
WHO should develop a laboratory manual for
dengue diagnosis.
WHO HQ should establish a global technical
advisory group, including representatives from collaborating centres, to meet
annually to advance laboratory training, capacity building, reagents, quality
issues, and DengueNet.
Reporting and information exchange
With regard to collection of laboratory data and information transfer,
the group identified a strong need for government health authorities to
develop a reporting system to collect, centralize, and disseminate these
data, identify key laboratories to participate in this system, and designate
a focal point for DengueNet.
The group recommended that WHO support national health ministries to
assess current laboratory status in Asia-Pacific countries and to plan
mechanisms to strengthen laboratories for DengueNet. A draft DengueNet
laboratory assessment tool is available for review and use.
The group expressed appreciation of the efforts made to develop
DengueNet and recommended that WHO work with partners to develop strategies
for raising crucial resources.
Recommendations of the epidemiology working group
The group reviewed currently available data and reporting practices in
the Asia-Pacific countries in relation to DengueNet. The discussion was
organized around the principal epidemiological variables of time, place and
personal characteristics, plus information about the virus. The group made
recommendations on the modifications to be made to the present format of the
DengueNet prototype in Global Atlas, on strengthening epidemiological
surveillance, and on a framework for implementation of the DengueNet in
Asia-Pacific regions with emphasis on the quality of available data and the
active participation of national programmes.
Data collection
Epidemiological data
 To accommodate currently available case
classification reporting practices, countries should provide three categories
– DF cases, DHF/DSS (dengue shock syndrome) cases, total dengue cases
(DF/DHF/DSS). These data should be provided monthly, at state/department
level by large countries and at island level by island nations.
Countries should provide data, monthly when
available, on “dengue deaths” (probable or confirmed).
Countries should provide annual
epidemiological data by sex and age groups.
Rate calculations
Both incidence and mortality rates should be
expressed per 100 000 mid-year population; countries should provide updates to
DengueNet in the event of significant change.
The system should not show incidence and
mortality rates for countries that report data only from sentinel sites.
Virus serotype data – all available
Data should be entered (when provided by the
laboratory) as the cumulative number of isolations of each serotype in the
country from 1 January.
General recommendations
For countries
Countries should promote implementation of the WHOrecommended
surveillance standards for dengue. (Participants were provided with copies of
these standards.)
For DengueNet
A country information page should be provided on the DengueNet web site
for all country-specific information, definitions, and methods used (e.g.
sentinel site information, reporting by time of onset or notification, case
classification other than according to the WHO definition, etc.).
WHO-recommended surveillance standards should be made available on the
DengueNet web site.
Roles and responsibilities of the partners in this network
Countries will collect, validate, and provide epidemiological and
laboratory data. They will designate the participating centres and focal
points, and WHO country offices will facilitate the process. WHO
collaborating centres will provide laboratory support, proficiency panels,
and training to national laboratories. WHO regional offices will implement
the country support activities, and WHO HQ will maintain and moderate the
DengueNet web site. WHO regional offices and HQ will seek financial support
for dengue surveillance activities.
Country participation
A major outcome of the meeting was that representatives of all participating
countries showed interest in collaborating with DengueNet and agreed to
present the meeting’s recommendations to their health ministries. Country
participation will require a letter of request from WHO to the ministry of
health; ministry authorization for participation and designation of a
national DengueNet focal point; and, for some countries, an external budget.
The DengueNet pilot will be expanded to countries in American,
South-East Asian, and Western Pacific regions in 2004 after modifications to
the system have been made in Global Atlas. The lessons learned from the pilot
will be used to develop a consensus framework for DengueNet implementation
for standardized global surveillance of dengue and DHF.
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