4. LEARNING OBJECTIVES
By the end of the session the learners would be able to
The epidemiology of Dengue fever
Clinical features of Dengue fever
Control and Prevention of Dengue Fever
6. DENGUE FEVER
It is a viral infection caused by dengue virus, capable of
infecting human and causing disease.
There are 4 serotypes of dengue virus, Each serotype
provides specific lifetime immunity.
All serotypes can cause severe and fatal disease
(DEN-1, DEN-2, DEN-3 and DEN-4).
Recovery from infection by one provides lifelong
immunity against that particular serotype.
However, cross-immunity to the other serotypes after
recovery is only partial and temporary.
Subsequent infections by other serotypes increase the
risk of developing severe dengue.
RESERVOIR OF INFECTION:
Both human being and mosquitoes.
Mosquitoes (aedes aegypti, aedes albopictus)
3 to 10 days
MODE OF TRANSMISSIOM:
By bite of infected aedes mosquitoe. 8
PERIOD OF COMMUNICABILITY:
Infection is not directly communicable from men to men.
All ages and both sexes are susceptible.
11. AEDES AEGYPTI
The Aedes aegypti mosquito lives in urban habitats and
breeds mostly in man-made containers.
Unlike other mosquitoes Ae. aegypti is a daytime feeder
Its peak biting periods are early in the morning and in
the evening before dusk.
Female Aedes aegypti bites multiple people during each
feeding period. 11
12. CASE DEFINITION
Suspected Dengue Case
Three or more of the following signs should be present
Fever Myalgia Rash Decreased
Headache Arthralgia Bleeding
Bone pain Abdominal pain
13. CASE DEFINITION
Probable Dengue Case
Suspected case with
Low platelets count ( less than 100,000/ mm3) and
low white cell count (less than 3000/mm3 )
IGM antibody detection
Or positive NS 1 antigen
+ve tourniquet test
Confirmed Dengue Case
Viral detection by PCR
14. LAB. TESTS
Up to 7 days – NS-1 ELISA
7-15 days – IgM ELISA
15th day onwards – IgG
Anytime during fever – Virus detection by PCR, cell culture
There is no specific treatment for dengue fever.
For severe dengue, medical care by physicians and
nurses experienced with the effects and progression of
the disease can save lives – decreasing mortality rates
from more than 20% to less than 1%.
Maintenance of the patient's body fluid volume is
critical to severe dengue care.
There is no vaccine to protect against dengue to date. 16
17. DEVELOPMENT OF EPIDEMIC CONTINGENCY PLANS
Contingency planning should involve estimating the
number of people at risk.
Determining the quantity of equipment (including
hospital beds and intensive care facilities)
Supplies and personnel required for vector control and
patient management and documenting the location of
Most urban hospitals would be expected to have these
quantities in stock.
Adjustments should be made to provide for the
population at risk in a given area and provisions made
for timely resupply in the case of an epidemic.
20. CONTROL OF DENGUE FEVER
To control outbreaks, two operations must be conducted
1. Emergency mosquito control and
2. Treatment of patients in hospital.
21. 1. EMERGENCY MOSQUITO CONTROL
The following steps should be immediately taken when
an outbreak of dengue or DHF is suspected:
Personal protective measures, the use of household
aerosol insecticides, source reduction efforts at home
and in the neighbourhood.
The geographical area should be defined in order to
determine the extent of the insecticide spraying
For this purpose, cases of dengue and DHF should be
confirmed in the laboratory by serological examination.
An inventory (list of stock) of the quantity and
availability of pesticides and the equipment for their
application should be made. 22
The objective of these measures is to eliminate infected
mosquitos and to break the transmission cycle by
reducing mosquito populations to extremely low levels/
Control of an epidemic may not be feasible if adult
populations of Ae. aegypti cannot be sufficiently
However, a sustained reduction of vector populations
will inevitably result in fewer cases. 23
24. 2. TREATMENT OF PATIENTS IN HOSPITAL.
An organizing or coordinating committee should be
established and should consist of administrators,
epidemiologists, clinicians, entomologists and workers
from virus laboratories.
The committee should:
1. Design and distribute protocols for the clinical
diagnosis and treatment of DHF/DSS.
2. Prepare and circulate information on DHF/DSS for
health care workers, the public and the press.
3. Plan and implement training programmes for health
care workers and auxiliaries (e.g. hospital staff, medical
students, nurses and laboratory technicians).
Assess the need for intravenous fluids, medications,
blood products, intensive care equipment, teaching
materials and equipment for transporting patients.
Supervise the use of supplies and the outcome of clinical
Coordinate clinical research on DHF/DSS during any
During epidemics, outpatient and inpatient facilities may
be overwhelmed and medical staff can rapidly become
In these circumstances, only those persons genuinely
requiring hospital care should be admitted.
A fever and a positive tourniquet test, or other
manifestations of bleeding, are sufficient for DHF to be
28. METHODS OF VECTOR PREVENTION & CONTROL
For success and sustainability WHO recommend Integrated Vector
Management with emphasis on larval source of reduction
1.Chemical Control: Larvicides, Indoor Residual Spray(IRS),
2.Environmental Management: Man- Vector contact reduction
3.Biological Control: larvivorous fish, Bacteria (Bacillus
Thuringiensis h- 14).
4. Genetic Control: Sterile male technique
5. Personal Protection: Bed- net, curtains, repellant, coils,
electric devices, etc.
6. Physical barriers oils, polystyrene beads, traps 29
dengue fever - high fever, normal platelet count, no petechiae, with nausea and vomiting, normal bp
life-threatening dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs.
the set of antigens that characterizes the group
The World Health Organisation (WHO) has defined this test as one of the necessary requirements for dengue fever diagnosis.