1. Epidemiology Clinical features Epidemiological Investigation
DENGUE
Epidemiology
Clinical features
Epidemiological Investigation

2. DENGUE Dengue Fever/DHF/DSS Mosquito Aedes aegypti Aedes albopictus
Infectious agent Dengue virus
4 serotypes
DEN-1,-2,-3,-4.
Infection to one serotype confers lifelong immunity to the serotype but not to the other 3

3. Aedes albopictus indigenous to Singapore, feed in one meal
Aedes aegypti imported after WWII, feed in multiple meals

5. Infectious Period Incubation Period 1 - 2 weeks
Up to 5 days after onset of illness
Infectious Period

6. Clinical Features
Dengue fever

7. Signs & symptoms Sudden fever Headache Muscle & joint pain
(“saddle-back” pattern)
Headache
Muscle & joint pain
Nausea/vomiting
Macular papular rash (D3-5 when fever subsides)

8. Petechial Rash

9. Dengue Serology IgG & IgM Haemagglutination WBC count
Laboratory Diagnosis
Dengue Serology IgG & IgM
Haemagglutination
WBC count

10. Dengue Haemorrhagic Fever/Dengue shock syndrome Associated with secondary infection of a different serotype Bleeding tendencies (platelet decreased) Fits/seizures or convulsions Mortality rate is 30% if not properly treated

11. 4 necessary criteria: Fever or recent history of acute fever
Hemorrhagic manifestations
Low platelet count (1000,000/cu mm or least)
Objective evidence of “leaky capillaries”
-elevated hematocrit (20% or more
over baseline). Packed cell volume (PCV) or erythrocyte volume fraction (EVF), is the volume percentage (%) of red blood cells in blood. It is normally about 45% for men and 40% for women.[
-low albumin
-Pleural or other effusion (excess fluid that accumulates between the two pleural layers, the fluid-filled space that surrounds the lungs.

12. Haemorrhagic Manifestations

14. Vector control strategies in Singapore
Launched in 1970
-Source reduction
Environmental control
-Elimination of larval habitats
in residential premises
-Public education
-Law enforcement
-Chemical control

16. Possible reasons for re-emergence of dengue
Lowered hers immunity
Alerted vector bionomics
Delayed infection- from childhood to adulthood
Changed in vector control
-From prevention to case response
“Swimming in the sea of dengue” Gubler DJ. Dengue Bulletin 2002, 26:

17. Lowered herd immunity

19. Seroprevalence in primary school children
Singapore- 6%
Ratchaburi Province, Thailand- 71%
Dominican Republic- 56%

22. Altered vector bionomics

24. House indices (Tan 1997). -Residence. Landed residential properties 2
House indices (Tan 1997) -Residence .Landed residential properties 2.1% .Apartments 0.6% -Non-residences .Construction sites 8.3% .Factories 7.8% .Vacant premises 14.6% .School 27.0% House indices (Chan et al 1971) -Slum houses 27.2% -Shop houses 16.4% -Apartment 5.0%

26. Delayed infection

27. Infection in adulthood vs childhood
Less likely to be subclinical with increased age of onset
Endermic stability (Coleman et al. Lancet 2001, 357: )

28. Changes in vector control strategy
Return to entomological based approach rather than case reactive
Involvement of the public (Ovitrap/gravitrap)
Lower importation of virus-control dengue outside of Singapore?
Lower susceptibility to dengue through antivirals as prophylaxis

30. Dengue vaccine approved for use in Singapore 5th October 2016
The Health Science Authority studied Dengvaxia vaccine since March, fast-tracked its approval process because of public health concerns. The decision was based on 24 studies conducted by vaccine manufacturer Sanofi Pasteur, which involved more than 41,000 people and showed the vaccine to be safe for use and effective against dengue.
Given in three doses over a year, the vaccine is approved for use in those aged between 12 and 45. Those outside this age group can be vaccinated if they so wish, but should seek a doctor's advice first. For people aged two to 16, Dengvaxia was shown to reduce the number of dengue cases by 60 per cent as compared with those who had not been vaccinated. This figure went up to 84 per cent when it came to preventing severe dengue infections in the same age group.
Additional studies showed that the vaccine was effective up to age 45, said the HSA.
But, though formulated against all four strains of the virus, the vaccine is less effective against the Den-1 and Den-2 strains, which account for three-quarters of the dengue cases here. Its efficacy is 50 per cent and 40 per cent respectively, compared with 75 per cent and 77 per cent for the other two strains.
Studies also showed that the vaccine provided better protection for those who had been exposed to the dengue virus than for those who had not, with efficacy at 81 per cent and 38 per cent respectively.