Page 122 - Journal of Special Operations Medicine - Fall 2014

Phase 2 (Ongoing) multivalent DENV positivity seen in these studies most
Of the 417 voluntary specimens tested to date, screening likely reflects a combination of increased prevalence of
and sample titration resulted in 55 of 417 samples with all four serotypes in dengue-endemic areas combined
NT (MN > 10) against at least one DENV serotype. with the extensive travel and exposure histories of these
50
This demonstrates an overall dengue exposure rate of personnel. Mitigation of this risk can be accomplished
13.2% (55 of 417) in the USASOC population tested through a combination of efforts, only some of which
thus far. are currently available. The use of personal protective
measures, when applied properly, provides a modicum
of protection. However, in the case of dengue, at least
Discussion one component of the DoD repellent system, sleeping
Disease Non-Battle Injury (DNBI) typically accounts under a bed net, provides less protection because the
for the majority of casualties occurring during armed vectors are day-biting mosquitoes. Regardless, the need
conflict. Dating back to antiquity, military history is rife for definitive field capable diagnostics and an effective
with examples of mission failure or operational ineffec- vaccine in the special operations community is clear.
tiveness being attributed to infectious disease. Dengue,
classified by the CDC and WHO as a neglected tropical It is acknowledged that potential exists for preservice
disease is expanding globally. Numerous reasons have exposure. Ultimately, the circumstances of the expo-
29
been proposed for this occurrence such as increased in- sure are relevant only in regard to the serotype. Once
ternational air travel, unplanned urbanization, defor- a Soldier is exposed to all four serotypes, there is no
estation, cargo transport, population growth, creation further risk of developing DHF regardless of when or
of man-made mosquito oviposition sites, and decay in where their exposure took place. However, being able
public health infrastructure. All of these factors have to document specific deployment-related exposures will
lead to the spread of competent mosquito vector into reinforce the use of personal protective measures, the
previously nonendemic areas, in particular the spread need for field diagnostics, and the addition of dengue
of Ae. albopictus, which is outcompeting Ae. aegypti in screening to the SRP protocol, all of which are goals of
many places and is a voracious human feeder. 30,31 the project.

Overseas contingency operations find our US military The results from this initial study provide an epide-
deployed to various dengue-endemic regions globally miologic baseline for dengue in USASOC. The project
and sometimes sequentially. This raises the risk of re- is expanding to include additional vector-borne febrile
peated exposures to, and infections with, multiple den- illnesses, and the results will serve as a foundation for
gue serotypes, which likely increases the risk for the future phases of the study in which exposures will be
development of more serious sequelae of DF, DHF, and geographically identified, exposure rates analyzed, and
DSS. The current lack of knowledge regarding the infec- breakdowns in current force health protection counter-
tion rate of the US military means any information on measures highlighted. Ultimately, this information will
dengue exposures in the force will be of great use to help guide commanders’ medical threat planning in en-
commanders to assess the medical threat in a given loca- demic areas, allow medical personnel on the ground to
tion, better enforce countermeasures, and subsequently better understand and respond to the medical threat to
decrease the DNBI risk to the force. their personnel, and drive the development of more ef-
fective threat countermeasures and policies.
Special Operations personnel typically receive a myriad
of vaccinations before deployment. These include vac-
cines against flaviviruses such as yellow fever and Japa- References
nese encephalitis, which could confound neutralization 1. Guzman MG, Alvarez M, Halstead HB. Secondary infec-
testing depending on when the Soldier received the vac- tions as a risk factor for dengue hemorrhagic fever/den-
cine. However, in this study, the initial positive-screened gue shock syndrome: a historical perspective and role of
32
results were end-titered, thus removing concern for antibody-dependent enhancement of infection. Arch Virol.
false-positives. 2013;158:1445–1459.
2. Sun P, Bauza K, Pal S, et al. Infection and activation of
human peripheral blood monocytes by dengue viruses
Although the sample size in this ongoing project is through the mechanism of antibody-dependent enhance-
relatively small and the results are by no means repre- ment. Virology. 2011;421:245–252.
sentative of all deployed US military personnel, the sero- 3. Benedict MQ, Levine R, Hawley W, Lounibos L. Spread
prevalence rate seen in this sampling of sera specimens of the tiger: global risk of invasion by the mosquito Aedes
underscores the legitimate risk of multiple exposures and albopictus. Vector Borne Zoonotic Dis. 2007;7:76–85.
therefore the potential for development of DHF/DSS. 4. Guzman MG, Kouri G. Dengue: an update. Lancet Infect
The proportionally increased numbers of subjects with Dis. 2002;2:33–42, doi:10.1016/S1473-3099(01)00171-2.

114 Journal of Special Operations Medicine Volume 14, Edition 3/Fall 2014