1. Infectious Diseases Surveillance in the Military
LTC (Dr) Vernon Lee
MBBS, PhD, FAMS, MPH,MBA
Singapore Armed Forces Biodefence Centre

2. Surveillance
“Timely surveillance system that collects information on epidemic prone diseases in order to trigger prompt health interventions”
Monitoring of infectious diseases that impact Singapore Armed Forces (SAF) servicemen and operations
Includes epidemiological analytics and mathematical modelling
Local disease outbreak surveillance
Regional and international disease situation, e.g. MERS-CoV, Ebola

3. Why Military Surveillance
Military personnel face unique physical and mental stressors
Impact on immunity
Close-proximity living and working environments
Conduit for transmission of diseases
Different health seeking behavioural patterns
The military among the first to detect pandemic influenza cases in Singapore in 1957, 1968 and 2009

4. Singapore Armed Forces’ Early Warning System
Acute Respiratory Illness (ARI) surveillance Programme
Since 2009 across 4 sentinel sites
Enteric Pathogen Prevalence Study
Nov 2013 to Nov 2014

5. ARI Surveillance Cases Acute onset
Fever >37.5 ºC with cough and/or sore throat
Controls
No acute onset fever or respiratory symptoms in past 14 days
Without any infectious disease
Nasal washes obtained
Tested at DSO National Laboratories
PCR for 17 viral and bacterial pathogens
Sequencing and characterisation where relevant
Questionnaire on demographics, clinical signs/symptoms, potential risk factors obtained

8. Utilising Surveillance Data For Medical Protection Policies : Influenza vaccination
2010
2011
2012
2013
2014

9. Effectiveness of seasonal influenza vaccinations
Ho et al, Influenza Other Respir Viruses Sep; 8(5): 557–566.
7,016 influenza cases
Vaccine efficacy against both influenza A(H1N1)pdm09 and influenza B were 84%
95% CI 78–88% and 79– 86%
Vaccine efficacy against influenza A(H3N2) was markedly lower at 33%, 95% CI 4% to 57%
Reduction in risk post-vaccination vs pre-vaccination in recruit camp
70% (RR = 0.30; 95% CI 0.11–0.84) for A(H1N1)pdm09
39% (RR = 0.61; 0.25 – 1.43) for A(H3N2)
75% (RR = 0.25; 95% CI 0.11–0.50) for influenza B

10. Influenza profiling and comparison with national data
MOH
SAF

11. Adenovirus Surveillance
Following successful implementation of influenza vaccination, there was an increasing trend of adenovirus being detected
Potential implementation of Adenovirus vaccination in the SAF
But are the strains detected similar to the vaccine strains?

13. Temporal Distribution of Adenovirus Types (Jun 2009 - Jul 2014)
Time 1
: Jun-09 to Dec-10 6
: Jan-12 to Mar-12 11
: Apr-13 to Jun-13 2
: Jan-11 to Mar-11 7
: Apr-12 to Jun-12 12
: Jul-13 to Sep-13 3
: Apr-11 to Jun-11 8
: Jul-12 to Sep-12 13
: Oct-13 to Dec-13 4
: Jul-11 to Sep-11 9
: Oct-12 to Dec-12 14
: Jan-14 to Mar-14 5
: Oct-11 to Dec-11 10
: Jan-13 to Mar-13 15
: Apr-14 to Jul14

14. Circulating Adenovirus Types (Jun 2009 - Jul 2014)
Frequency E*
671 C1 40 C2 51 C5 23 C6 2 B3 92
B7* 42
B21 9
B55 1 B 30 U 10
Total (including 20 co-infections
971

15. Sequencing of hexon gene from Adenovirus B7

16. Sequencing of hexon gene from Adenovirus B7

17. Enteric Disease Surveillance

18. Enteric Pathogen Prevalence Study
The selection criteria of cases include:
Acute onset
At least 3 times watery stool and/or 2 times vomiting within 24 hours; and
For controls, the selection criteria include:
Patients without diarrhoea or vomiting in last 14 days; and
Without disease suggestive of an infectious cause
702 subjects recruited over 1 year

19. Pathogen prevalence Chart:

20. GID-related viruses trends

21. GID-related viruses trends

22. GID-related viruses trends

23. GID-related Bacteria Trends

24. GID-related Parasites Trends

25. Emergence of norovirus GI.2 outbreaks in military camps in Singapore
ZJM Ho et al, Int J Infect Dis. 2015 Feb;31:23-30.
Simultaneous gastroenteritis outbreaks at 2 camps
775 persons involved
Camp A (21 days, attack rate 15.0%). Camp B (6 days, attack rate 8.3%)
Investigations included epidemiological surveys, hygiene inspections, and testing of water, food, and stools
PCR and sequencing of relevant samples

26. Findings
Norovirus GI.2 detected in 32.5% (larger camp) and 28.6% (smaller camp) of stool samples
Identical to norovirus detected in two preceding community outbreaks
Antigenic site homology modelling showed differences with more common norovirus GII.4
Greater propensity for transmission within large camps with a high population density?
Why do certain noroviruses cause outbreaks?

28. Future surveillance programs
Routine enteric disease surveillance
Future extension to other febrile illness and returning travellers
Setting outbreak detection thresholds through modelling of surveillance data
Sero-epidemiology studies for vaccine-preventable diseases

29. Thank You