AN EXAMINATION OF SCENARIOS IN DENGUE FEVER TRANSMISSION WITH CONSIDERATIONS IN VECTOR CONTROL,

BLOOD DONATION, AND HEALTH COMMUNICATIONS IN THE UNITED STATES

by

Eric C. Andes

BS, Biological Sciences and Anthropology University of Pittsburgh, 2012

Submitted to the Graduate Faculty of

Graduate School of Public Health in partial fulfillment

of the requirements for the degree of

Master of Public Health

University of Pittsburgh

2014

UNIVERSITY OF PITTSBURGH

Graduate School of Public Health

This essay was submitted

by

Eric C Andes

onApril 21, 2014

and approved by

Essay Advisor:James Peterson, PhD ______________________________________Associate Professor Environmental and Occupational Health DepartmentGraduate School of Public HealthUniversity of Pittsburgh

Essay Reader:Bruce Pitt, PhD ______________________________________Professor and Chair Environmental and Occupational HealthGraduate School of Public HealthUniversity of Pittsburgh

Essay Reader:Elizabeth M. Felter, DrPH ______________________________________Visiting Assistant Professor Behavioral and Community Health SciencesGraduate School of Public HealthUniversity of Pittsburgh

ii

Copyright © by Eric C. Andes2014

iii

ABSTRACT

iv

Dengue virus (DENV) is a pathogen transferred via mosquito vectors causing dengue

fever (DF). DF is a growing concern for public health officials globally. In particular, DENV is

of major concern because there is no treatment targeting the virus, vaccine development is

problematic, and the number of cases is increasing dramatically. Furthermore, DENV infection

can be asymptomatic and can unwittingly be contracted through transfusion of blood products

from an infected donor. The United States has not yet experienced large scale DENV outbreaks,

but given global climate change it is only a matter of time before dengue becomes of importance

to public health in the United States. Preparation and planning of appropriate communication

strategies, vector management principles, and blood banking practices can allow for the United

States to address different scenarios of DENV transmission. This allows for the mitigation of

risk to communities and the protection of public health.

v

James Peterson, PhD

AN EXAMINATION OF SCENARIOS IN DENGUE FEVER TRANSMISSION WITH CONSIDERATIONS IN VECTOR CONTROL,

BLOOD DONATION, AND HEALTH COMMUNICATIONS IN THE UNITED STATES

Eric C. Andes, MPH

University of Pittsburgh, 2014

TABLE OF CONTENTS

I. INTRODUCTION: WHAT IS DENGUE? …………….………………………………………1

A. THE PATHOGEN …………...………………………………………………………..2

B. THE VECTORS ...……………………………………………………………………..4

C. EMERGING AREAS OF CONCERN ...…………………………..………………….61. Climate Change and Vector Distribution ...…………………………………….62. Vaccine Development ...…………………………..……………………………73. Blood Supply Safety ...……………………………………………………........8

D. SUMMARY……………………………………………………………………………9

II. SCENARIOS FOR DENGUE TRANSMISSION ...…………………………………………10

A. RELEVANT INFORMATION ...……………………………………………….……101. Management of Mosquito Vectors ………….....………………………….…..102. Basics of Risk Communication …....………………………………………….12

B. THE INITIAL OUTBREAK SCENARIO ...………………………………………....151. Environmental Management Focus ...………………………………………...152. Blood Collection Focus ...…………………………………………………..…163. Communication Focus ...……………………………………………………...16

C. THE SEASONAL OUTBREAK SCENARIO ...…………………………………….171. Environmental Management Focus .....……………………………………….182. Blood Collection Focus ….……………………………………………………183. Communication Focus ……..…………………………………………………19

D. THE ENDEMIC SCENARIO ...……………………………………..……………….191. Environmental Management Focus ….……………………………………….202. Blood Collection Focus ….……………………………………………………203. Communication Focus …..……………………………………………………20

III. FUTURE DIRECTIONS: WHAT CAN WE DO BETTER? ………………………….……21

A. BLOOD SAFETY AND DONOR RETENTION ….…………………..……………21

B. COMMUNICATIONS ….……………………………………………………………22

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C. VECTOR AND PATHOGEN CONTROL …..………………………………………22

IV. CONCLUSIONS…………………………………………………………………………….23

BIBLIOGRAPHY ……………………………………………………………………………….24

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LIST OF FIGURES

Figure 1. Vector life cycle highlighting key events and points of interest of vectortransmission…………………………………..………..……………………….1

I. INTRODUCTION: WHAT IS DENGUE?

Dengue Fever (DF), Dengue Hemorrhagic Fever (DHF), and Dengue Shock Syndrome

(DSS) are a cluster of clinical manifestations that occur as a result of infection by the Dengue

Virus (DENV). DENV infection and spread by mosquito vectors covers a number of critical

points of interest for public health officials. Globally there has been a rapid expansion of the

range of the mosquito vectors and a 30-fold increase in cases of DF. This in large part is due to

increased urbanization, population expansion, and climate change (WHO, 2012). As a blood

borne infection, DF and more serious clinical manifestations, present challenges to blood

banking systems, threatening the safety and security of the available fresh blood supply.

Additionally, elimination of potential blood donors during outbreaks limits the availability of

blood products. This is an issue because 100% donor efficiency is extremely difficult to achieve

for blood collection services even in the United States. (WHO, 2013). Of additional concern to

public health officials is the environmental management of mosquito vectors, as well as health

communications surrounding disease transmission, outbreak progression, and health education to

reduce risk of DENV infection. The factors listed above, as well as others, are important since

the increasing geographical range of vectors and DF introducing the virus to previously

unexposed populations in the United States.

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A. THE PATHOGEN

The pathogen is the dengue virus (DENV), an arbovirus in Flaviviridae, characterized by

a single strand of RNA, approximately 11 Kb in length, with a lipid envelope containing glycol

proteins unique to specific viral serotype (Guzman et al., 2010). DENV has four identified

serotypes important to human health referred to as DENV1-4 (CDC, 2014). Infection by one

serotype provides life-long immunity to that specific virus, but not to other serotypes.

Additionally, sequential infection by different serotypes is shown to have increased risk for

development of more serious forms of dengue, such as DHF Infection by DENV in many cases

can be asymptomatic, and often can go unnoticed. DF causes flu-like symptoms including fever,

nausea, vomiting, rash, aches, and pains (CDC, 2013). DF can progress to more severe

manifestations such as dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS).

DHF is characterized by the presentation of the same symptoms as DF; additionally, DHF causes

plasma leakage, liver enlargement, and impairs the central nervous system (CNS). Abdominal

pain is a sign of worsening condition and patients may show a hemorrhagic tendency

(Hadinegoro, 2012). In DSS, the most severe form of dengue infection, patients have increased

leakage of plasma, rapid/weak pulse, and hypotension compared to standards for the patient’s

age group (Hadinegoro, 2012). DSS and DHF are more likely to result in mortality while DF

itself usually is over after a recovery period of about 3 weeks (Mayo Clinic, 2012). There is no

treatment available that targets the virus. Current medical practice is palliative emphasizing

maintenance of fluids, and support for other symptoms (WHO, 2012).

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The transmission cycle for dengue fever (Figure 1.) is a complex interplay of contact

between, mosquito vectors, specifically Ae. aegypti and Ae. albopictus, human populations, and

non-human primate populations. There are two ways for a vector to become infected with

dengue virus. The first is for a vector to feed on a viremic host. When the mosquito feeds, the

virus is picked up through the blood meal, crosses the gut barrier in the mosquito, and eventually

is present in the salivary glands (Lee and Rohani, 2005). The process takes approximately 8-10

days (Mayo Clinic, 2010). Once in the salivary glands the mosquito is then able to transfer

DENV to other hosts during additional feeding events (WHO, 2013).

3

A second method of transmission of the virus is during the vector life cycle. DENV is

able to cross over from infected female mosquitos into their offspring in a form of vertical

transmission in the ovaries (Lee and Rohani, 2005). Although this is a less likely then a

mosquito picking up the virus from a viremic host, it is theorized that vertical transmission

allows for DENV to persist in mosquito populations during less than optimal environmental

conditions for survival (Lee and Rohani, 2005).

B. THE VECTORS

There are two important DENV vectors. a.) Aedes aegypti, the primary vector important

in urban environments; and b.) Aedes albopictus, a secondary vector important in suburban and

rural environments (Becker N. et al., 2010). Both vectors are members of the subgenus

Stegomyia and, are generally smaller in size than other subgenera of mosquitoes. These species

have a dark coloring and distinctive white markings of bands or spots. Typical of transmission

of arboviruses, the feeding habits of the female mosquito are important. Female mosquitoes feed

on the blood of various hosts (humans are the most preferable); and viral pathogens are then

transmitted through the salivary glands during feeding events (Becker et al., 2010).

The typical lifecycle of these vectors (Figure 1, bottom portion) lasts on average 30-40

days in the wild (Brady et al., 2014, Becker et al., 2010, and Mayo Clinic, 2012). The eggs of

Ae. aegypti and Ae. albopictus are laid in artificial water containers although both species may

utilize natural containers if present (Becker et al., 2010). The eggs themselves are resistant to

desiccation. Thereby, allowing them to survive periods of time when water amount is not

optimal for hatching (Becke. et al., 2010). After 1-2 days in the surface of waters containing a

mild amount of organic content, but generally is not very turbid, the eggs hatch into mobile

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larvae which feed on the organic content (Becker N. et al., 2010). These undergo 4 instar forms

over 4-5 days before forming pupae and entering metamorphosis, which takes approximately 2

days (Becker N. et al., 2010). Adult mosquitos emerge from metamorphosis and within 1-2

days, females will seek a blood meal that is typically a human host (Becker et al., 2010).

Although both vectors have similar life cycles, their distribution varies due to differences

in ability to survive extreme temperatures. Ae. aegypti has an optimal temperature range of 27-

30°C and is unable to survive in temperatures below 10°C. This limits Ae. aegypti to areas that

do not have cold winters. In regions with cold weather, Ae. aegypti occurrence is limited to

warm/wet months (Becker et al., 2010). In general, Ae. aegypti is limited to tropics, sub-tropics,

and warm temperate regions (Becker et al., 2010).

Ae. albopictus differs from Ae. aegypti in that its eggs are able to enter a diapause during

cold temperatures. This adaptation allows for eggs to lay dormant through cold winter

temperatures and hatch upon warming when sufficient water levels are apparent (Becker N. et

al., 2010). Consequently, the geographic range of Ae. albopictus is much larger and brings the

vector into contact with a wider range of human populations. Additionally, Ae. albopictus is less

selective in its host feeding preferences and is known to feed on humans, other mammals, and

avian hosts (Becker N. et al., 2010). Traditionally Ae. albopictus was geographically constrained

to East Asian countries, providing the non-taxonomic name of the Asian tiger mosquito, but with

an increase in global trade ,in particular rubber tires, the species has been able to disseminate

globally. It was first detected in the United States in Houston, Texas in 1985 (Becker N. et al.,

2010) and has reached as far as areas of Northeast United States (ACHD, 2013).

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C. EMERGING AREAS OF CONCERN

1. Climate Change and Vector Distribution

Climate change and variability are shown to influence mosquito survival and distribution.

This has led to an increase in the spread of pathogens. As a result of range expansion, mosquito

vectors and human populations come into increasing contact for longer periods (Johansson et al.,

2009 and Morin, 2013). Two primary factors that have importance for vector distribution are

temperature and precipitation (Johansson et al., 2009 and Ramasamy, 2012). There are also

secondary climate change effects that can have important impacts on vector distribution such as

changes in flora and fauna, as well as a rise in sea levels (Ramasamy, 2012). There is an

expected increase over the course of the 21st century in temperature, shifts in precipitation, and a

rise in sea levels as oceans warm (Collins et al., 2013)(Church et al., 2013). Additionally, it is

predicted that there will be an increase in extreme warm weather events and a decrease in

extreme cold weather events (Collins et al., 2013).

Unless significant changes are made in anthropogenic sources of climate change, these

factors (especially temperature and precipitation) will continue to influence vector distribution

and disease transmission (Morin, 2013). The survival of adult female Ae. aegypti, and Ae.

albopictus is important in the transmission cycle of DENV. The more that survive the more

vectors that are available to transmit the virus, and the higher potential there is for an outbreak of

DF (Brady et al., 2013). A culmination of experiments was utilized to determine temperature

ranges of both species in laboratory and field settings which indicate increases in temperature

will expand regions with ideal conditions for mosquito survival (Brady s et al., 2013).

Additional modeling of the data showed that Ae. aegypti is able to survive in a wider range of

temperatures but Ae. albopictus is better at overall survival.

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Precipitation is also an important primary climate factor in dengue transmission.

Although it is unclear what aspect of precipitation is critical to understanding relationships to

transmission of DENV and vector survival (Johansson et al., 2009), an increase in humidity and

moisture in an area would generally accompany an increase in available breeding sites, providing

a more suitable environment for mosquito vectors to reproduce.

Temperature and precipitation also have secondary impacts that can lead to an increase in

the range and distribution of mosquito vectors primarily through the distribution of flora and

fauna, and through a rise in sea levels (Ramasamy, 2012). As climate change progresses and the

water cycle shifts precipitation at higher latitudes is occurring (Collins et al., 2013). This

precipitation change and the accompanied temperature changes allow for local flora and fauna to

change their geographic distribution, typically with species moving to higher latitudes following

the water cycle (Ramasamy, 2012). Changes in flora can provide new breeding grounds for

vectors, while changes in fauna can allow vectors to survive in new regions as the distribution of

potential hosts shift (Ramasamy, 2012).

Climate change may affect sea level (Church et al. 2013). On a global scale this will

create additional environments for the breeding of mosquito vectors, in particular those vectors

that are able to tolerate salinity (Ramasamy, 2012). This allows for vector distribution along

coastal regions to readily occur and disseminates vectors to large populations that live near

coasts especially along the Eastern coast in the United States (Ramasamy, 2012).

2. Vaccination Development

Currently the best methods utilized for managing dengue is vector control. Strategies to

disrupt the transmission cycle include; a.) intervention in life cycle of vectors thereby, preventing

transmission of the pathogen between vectors and susceptible populations; or b.) immunizing

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populations to DENV. Immunization is unfortunately not a currently viable method of control at

this point in time. Vaccine development is routinely complicated and this is particularly the case

for DENV due to multiple serotypes of dengue (Wan et al., 2013). For a vaccine to effectively

provide immunization it has to protect against all four serotypes of DENV. Without complete

protection a population will be primed for an outbreak that could lead to a high number of DHF

cases and DSS (Wan et al., 2013).

Additionally, the recent discovery of a fifth viral serotype, DENV-5, further complicates

vaccine development (Normile, 2013). The discovery and subsequent investigation of this new

serotype showed that it was responsible for an outbreak of DF in Malaysia in 2007 (Normile,

2013). This serotype is still in a sylvatic cycle (Figure 1.) utilizing macaques as a host and is

only able to cause disease in human populations that exist within close proximity to non-human

primate populations and mosquito vectors (Normile, 2013). If DENV-5 is able to mutate and

sustain a transmission cycle in human populations, vaccine development will be further

complicated (Vasilakis et al., 2011).

3. Blood Supply Safety

DENV infection, particularly in endemic regions, has the ability to be asymptomatic. As

a result, individuals who are infected with the virus will be able to participate in donating blood

even when they are unwittingly carrying an agent that is transferable through transfusion. This

leads to the development of infections from transfusion, and has been documented in Puerto

Rico, Hong Kong, and Singapore (Katz, 2010; Wilder-Smith, 2009, Tambyah et al., 2008; and

American Red Cross, 2014). The safety of the blood supply can be secured by the utilization of

screening of potential donors and blood products. In the United States the blood supply is not

routinely screened for DENV (American Red Cross, 2014 and Katz, 2010). General practice

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rather, is to screen donors prior to donation. In regards to dengue fever, it is currently the

standard to defer a donor from the process for 120 days after clearing infection by DENV (Katz,

2010). While this is effective to eliminate DENV contamination, it is a very long period of time

to defer a potential donor especially when red blood cells can be collected once every 56 days

(American Red Cross, 214), effectively limiting an individual from being able to donate two to

three units depending on the length of recovery or severity of disease (American Red Cross,

2014 and Katz, 2010). It is recommended that this period be shortened and research be expanded

in understanding the disease process of DENV (Wilder-Smith, 2009 and Katz, 2010). In the case

of recurring outbreaks and endemic levels of disease, the number of donors will begin to

decrease and blood shortages will become an issue for transfusion practices (Montenegro, 2011).

In particular, the demand for platelets will be of special concern as donated platelets are only

viable for transfusion for 5 days making it impossible to have a large supply stored in case of

emergent situations (American Red Cross, 2014 and Montenegro, 2011). As dengue becomes a

larger health concern, the need to develop assays for screening of units is imperative. Costs for

screening may be mitigated if risk is taken into account (Katz, 2010).

D. SUMMARY

DENV, as a result is of major concern to public health. The lack of treatments for the

virus and the spread of vectors will bring new populations into contact with DENV that have not

seen the disease. Additionally, the limitation of fresh blood and blood products, through donor

deferral, allows DENV to impact health systems outside of being an agent of disease. Shortages

will require screening and managerial efforts to meet demand. Fortunately, for unexposed

9

regions (such as the United States) there is time for planning of management strategies/programs

for handling vector distribution and blood collection processes.

II. SCENARIOS FOR DENGUE TRANSMISSION

The issue of DF and how it interacts with populations depends on a complex web of

environmental conditions, presence of the pathogen in vector populations, and prior outbreaks of

DENV in populations. Consideration of the initial, seasonal, and endemic outbreaks are three

important scenarios in developing a strategy. Each scenario has different challenges for the

public health practitioner in environmental control, blood collections, and risk communication

A. RELEVANT INFORMATION

In order to examine the challenges that will be encountered. A working knowledge of

environmental control methods for mosquito vectors will be useful. Additionally, basic

fundaments in risk communication and risk communication theory are necessary in order to

understand communication challenges in each scenario.

1. Management of Mosquito Vectors

The management of mosquito vectors is focused on the disruption of transmission cycles

or the disruption of the vector life cycle. Management of mosquito vectors can be achieved

through biological control, environmental management, chemical control, physical control, and

genetic control (Becker et al., 2010).

Biological control measures utilize other organisms as a means to reduce mosquito

populations to acceptable levels. Predators, microbes, pathogens, and parasites are examples of

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biological control methods. In general, biological control is complicated by a need to preserve

ecosystem stability, and should be utilized as part of a comprehensive program for vector control

(Becker et al., 2010). Utilizing complete knowledge of the biology of the agent helps to ensure

that biological control programs are successful, and solve the mosquito problem without

disrupting the status quo of the ecosystem (Becker et al., 2010). In order to prevent negative

effects, it is recommended that the promotion of organisms that are already present in an

ecosystem be utilized as antagonists to mosquito populations. This strategy is designed to avoid

the possibility of displacement or introduction of invasive species. Mosquitocidal bacteria are a

useful biological control agent. The toxins contained in these strains of bacteria are consumed

by larvae and are extremely selective in toxicity to mosquitoes making them environmentally

safe (Becker et al., 2010). Additionally, mosquito species are less able to become resistant to

bacterial than chemical control measures (Becker et al., 2010).

Environmental management of mosquito vectors is accomplished through the

modification and manipulation of the vector habitat in order to decrease potential breeding sites

(Becker et al., 2010). In urban environments, construction goals should include a reduction of

potential breeding sites, specifically focusing on preventing accumulation of water in drainage

systems, sewage and water processing systems, and cemeteries (Becker et al., 2010).

Chemical control (insecticides) of mosquito vectors uses four broad categories of

treatments to reduce mosquito populations including: chlorinated hydrocarbons,

organophosphates (OPs), carbamates, and pyrethroids (Becker et al., 2010). Although effective,

many chemicals negatively impact non-target organisms. A prime example is

dichlorodiphenyltrichloroethane (DDT). Coupled with issues of vector resistance and increasing

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dosage requirements, there have been growing concerns about the efficacy of chemical

treatments, as well as concern for environmental health and toxicity (Becker et al., 2010).

Physical control of mosquito vectors seeks to physically gather and isolate mosquitos and

is not associated with the development of resistance (Becker et al., 2010). Oils, surface films,

bead beds, and traps are all forms of physical control of mosquito vectors. Each method seeks to

isolate and halt the mosquito life cycle and interrupting the chain of transmission (Becker et al.,

2010).

Genetic control of mosquitoes refers to technologies and methods centered on sterile

insect techniques (SIT) or the prevention of infection by pathogens important to human health.

SIT methods of mosquito control seek to cause changes in the mosquito population that interrupt

the mating cycle by preventing viable offspring from developing (Becker et al., 2010). For

example the release of a population of sterile male mosquitoes will effectively prevent viable

eggs from being deposited eliminating the next generation (Becker et al., 2010). Technologies

that exist to prevent pathogen infection seek to cause genetic changes in mosquito populations

that make them resistant to infection by pathogens (Becker et al., 2010). In DF this would mean

introducing genetic changes that lead to a phenotype that prevents DENV from entering female

mosquitoes during their first blood meal (Figure 1).

2. Basics of Risk Communication

There are a number of techniques that can be utilized to control mosquito vectors, but

most importantly methods must be coupled with community participation/education, and with

each other to form integrated control measures (Becker et al., 2010). Many methods of control

require participation by the community to be truly effective and this can only be achieved

through effective health and risk communications between oversight agencies and communities.

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Risk communication is a basic element of any program involving human health. With

the integration of communities into mosquito vector control programs, it is important to keep in

mind that the general populace and industry/oversight agencies will have different concerns and

perceptions of risk (Sandman, 1993 and Slovic, 1987). It is important that all perceptions of risk

be taken into account and that communication strategies encompass all perceptions in order to

reach the community and create effective vector control programs.

It is useful to consider risk in the contest of hazard and outrage (Sandman, 1993). Hazard

is the technical component of risk. Hazard is what industry and regulatory agencies would

consider as the risk assessment process. For example, hazard would be the chance of developing

cancer when exposed to a defined level of carcinogen. Hazard represents a quantified analysis of

the likelihood of negative impacts to health of a specific agent or activity (Sandman, 1993).

Outrage is the non-technical reaction to a hazard. Unlike hazard it is more difficult to measure,

but it is equally as important as hazard because it plays a large role in determining how to

address a communications problem (Sandman, 1993). Even if hazard is intrinsically low for a

particular agent or activity, the outrage factor can make the regulation and management of the

situation more complex and crucial (Sandman, 1993). In the case of mosquito vectors, it is

important not to just understand the hazards (the chances of contracting DF) but also

understanding the outrage, reactions of communities to regulatory measures and their concerns

over treatment methods, in order to achieve a suitable management strategy.

Outrage is influenced by a number of factors. For example, if an event is voluntary,

natural, familiar, chronic, and well known, then it is likely that the outrage level of a community

is relatively low (Sandman, 1993). Conversely, if an event or agent is of industrial or man-made

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origins, rare or exotic, catastrophic, unknown, coerced, or forced upon a community, it is likely

that there will be much higher levels of outrage to contend with (Sandman, 1993).

When risk is appropriately examined, and hazard and outrage are determined, it is

possible to begin to look at theoretical underpinnings on how to frame a communication plan.

When examining different scenarios it is important to keep in mind that risk perception will be

changing from scenario to scenario, and thus the Risk Perception Model will be of use. The Risk

Perception Model suggests that examining the perceptions of risk in the community and tailoring

communications to addressing these perceptions is the primary goal of risk communication

(Covello et al., 2001). This is especially important when outrage has become a major barrier in

communications (Sandman, 1993).

Additionally, in different scenarios the level of stress faced by individuals will vary. The

Mental Noise Model addresses situations of high stress, i.e. mental noise (Covello et al., 2001).

Under high mental noise situations it may be difficult to communicate to individuals. This is

large in part due to a diminished capacity to handle information from high levels of stress. As a

result communication messages should be tailored to address the impaired ability of people to

process information (Covello et al., 2001). This is achieved through short messages and

instructions aimed at reducing immediate risks present in the situation (Covello et al., 2001).

The Negative Dominance Model for risk communication suggests that information

associated with negative and positive trains of thought are treated differently and given different

weights by individuals (Covello et al., 2001). Negative messages are typically given closer

attention and should be counterbalanced by a larger number of positive messages (Covello et al,.

2001). This should be given considerable attention when a donor is prevented from giving blood

and blood products to a collection service. Furthermore, the additional weight given to negative

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messages can be utilized to emphasize actions to take to reduce overall risk of populations.

Message can be tailored to utilize negative statements such as “don’t” or “never” in order to

prevent higher risk actions (Covello et al., 2010).

Finally, establishing trust is imperative for risk communication. The Trust Determination

Model suggests that building trust takes time, and is bolstered by working to present one

communication strategy from a trusted source with transparency and frequent updates as

information becomes available (Covello et al., 2001).

B. THE INITIAL OUTBREAK SCENARIO

The initial outbreak scenario is characterized by a one-time initial outbreak of DENV into

a susceptible population. In this case, vectors most likely are newly established due to favorable

climate for expansion and survival, and likely will not maintain a permanent presence once

conditions are below thresholds for mating and development. A large proportion of the

population does not have immunity since DENV has never been encountered and anyone with

immunity likely has been exposed during travel to other regions.

1. Environmental Management Focus

Since the disease vectors likely are newly introduced, environmental management should

focus on education and dissemination of information on mosquito breeding sites, and feeding

habits. It is likely that elimination of breeding sites on personal property will be enough to

interrupt the life cycle, but the additional use of chemical sprays may be utilized. Long term

management of vectors is not of a concern at this point in time because this is a rare one-time

event that can be handled on an as need basis.

15

2. Blood Collection Focus

Standard operating procedures for collection services should suffice in preventing

introduction of pathogens into the blood supply. Eliminating donors before the donation process

through screening for symptoms, and waiting until infection has cleared in the community should

be effective methods to maintain security of transfusion of products. The 120 day waiting period

for donor deferral will allow the pathogen to be effectively cleared preserving the safety of the

blood supply. If needed it is possible to import units in from neighboring blood system. Regions

not experiencing outbreaks of DF can help to meet the demand for blood and blood products.

3. Communication Focus

Risk in the case of the initial outbreak is governed primarily through the outrage level.

The hazards of infection by DENV are low in this scenario since the likelihood of more serious

forms of DF such as DHF and DSS as there was no prior infection by different viral serotypes.

Additionally, the elimination of viable breeding sites within an individual’s property will most

likely be able to limit contact with mosquito vector preventing disease transmission. The outrage

levels are high in this situation due to this being an exotic and rare event. The disease process to

the community will be relatively unknown, and a lack of experience in dealing with mosquito

vectors of DENV can generate a high level of stress making the Mental Noise Model a useful

theory for risk communication. Of additional concern will be the high levels of concern and

mental stress surrounding the impacts these outbreaks will have on child health. Communication

strategies will have to address the high levels of mental noise present by calming fears

concerning the outbreak. Communication efforts should be short and succinct coming from the

local health authorities, as recommended under the Trust Determination Model, giving people a

list of behaviors to not to perform in order to reduce hazard. For example, explaining to not

16

leave containers of stagnant water sitting out would be utilizing the Mental Noise Theory to

enforce a behavior that eliminates breeding sites and reduces hazard while addressing the levels

of stress the community/population will be experiencing.

The Trust Determination Model will also be integral in communicating the continued

safety of the blood supply. Messages should emphasize continued efforts to ensure the safety of

blood products and collection services need to maintain transparency on the status of the blood

supply. Updates should be frequent and regular in order to maintain the trust of the public. The

Mental Noise Theory and Negative Dominance Theory will also be useful to handle the high

levels of mental stress and negative implications of blood shortages. Additionally,

communications need to find ways to ensure that viable donors are reached and donate blood

products to meet demand.

C. THE SEASONAL OUTBREAK SCENARIO

The seasonal outbreak scenario is characterized by the regular outbreak of DENV as a

result of local climate patterns. During the wet and warm season vector populations lying

dormant through diapause, or neighboring vector populations spurred by favorable conditions,

begin establishing themselves in higher numbers compared to the initial outbreak. Proportions of

the population that have already been exposed to DENV will maintain their immunity, unless a

new viral serotype is introduced. The introduction of a new serotype will increase the chances of

an individual developing more serious forms of DF such as DHF and DSS.

17

1. Environmental Management Focus

As outbreaks have shifted from being rare occurrences to annual incidents, environmental

management may focus on large scale projects to eliminate important sources of stagnant water

for breeding sites. This may include updating and revising infrastructure in the waste and storm

water collection systems, as well as the modification of nearby wetlands. There should also be a

continued effort to include local communities in the management effort through continued efforts

at limiting exposure on private property by limiting breeding sties. Additionally, areas that are

known to be likely mosquito breeding hotspots, such as cemeteries or construction sites should

be closely monitored for activity. Long term prevention strategies should be developed such as

spraying schedules for insecticidal efforts that coincide with the seasonality of the outbreaks to

limit vector populations from becoming unmanageable.

2. Blood Collection Focus

Stricter criteria for donation may be need to be established including performance of

medical examinations to determine donor status. Collection services may either consider

screening units of blood for DENV infection if transfusion associated infections are a concern.

Additionally, during seasonal outbreaks the potential stockpiling of products such as red blood

cells and plasma may be considered prior to the outbreak season to alleviate issues of donor

deferral during the event. Transfusion of short shelf life products such as platelets should be

carefully considered to maintain the stock to prevent shortages during emergent situations and

clinical practice should perform platelet counts to determine patient need of platelet pools prior

to transfusion.

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3. Communication Focus

Risk communication during the seasonal outbreak scenario should focus on the

increasing hazard levels as a result of the potential introduction of new viral serotypes to a

population. Additionally, the outrage level will have dropped from the initial outbreak since

DENV outbreaks are a seasonal annual event, no longer making them exotic and rare. Outrage is

still a concern because anxiety will be felt over the depletion of blood products, and concerns of

the safety of the blood system from pathogens increases. Fortunately there is the ability to

prepare the community in advance for the seasonal outbreak and messages prior to the outbreak

should focus on the Trust Determination Model, and the Risk Perception Model for

communication approaches. These efforts should address public concern over the outbreak and

what the perceived level of risk is by providing expert advice on how to limit exposure to vectors

and the virus. Additionally, during the outbreak, it is likely that there will be significant levels of

stress making the Mental Noise Model applicable to help limit exposures and hazard. Finally,

the increase in donor deferral for blood collection services will need to utilize the Negative

Dominance Model. In order to curb the potential shortages of blood products positive messages

that give deferred donors opportunities to still be involved and participate in the donation process

hopefully may be effective in decreasing the burden of shortages on the healthcare system.

D. THE ENDEMIC SCENARIO

The endemic scenario is characterized by a year round presence of DENV and

introduction of multiple serotypes. There will be seasonal variance in the degree of infection as

a result of improved conditions for vector survival. Cases of DHF and DSS will be more likely

as a result of infection by different viral serotypes.

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1. Environmental Management Focus

Environmental management should focus on creating integrated management plans that

focus on utilizing a wider array of methods to temper mosquito populations. The use of

biological control through the maintenance of natural predators may be a viable option.

Additionally, if vector populations are becoming increasingly unmanageable introduction of

predators may be required. Investment into bacterial control of vectors and genetic sterilization

techniques should be considered and large projects to update infrastructure to eliminate breeding

sites should be undertaken immediately. Community involvement in the elimination of private

property breeding sites should be a year round activity.

2. Blood Collection Focus

Blood collection systems should spend the time and money on a full screening process of

donated units of blood products. Products should be quarantined from available stock until

testing has confirmed it to be negative for DENV. Additionally, increased screening prior to

donation should be utilized to try and alleviate the cost of screening the entire supply. In the

case of an endemic scenario airing on the side of caution may be necessary even if it results in

the deferral of some donors who do meet qualifications for donation.

3. Communication Focus

Communication efforts will now be confronted with a scenario with high hazard, and a

decrease in outrage. Hazard has increased as the multiple serotypes and subsequent infections

become more common place. These will lead to an increase in cases of DHF and development

of DSS. Outrage will have decreased because DF is a year round threat and will have lost its

status as a rare or exotic disease. Additionally, dengue will be accepted as an element of the

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environment and something that is out of the control of the individual. Communications should

emphasize the Risk Perception Model since the perception of risk will govern an individual’s

actions. Additionally the Negative Dominance Theory will play an increasing role in blood

donation activities as deferrals continue to occur and increase in frequency.

III. FUTURE DIRECTIONS: WHAT CAN WE DO BETTER?

Dengue is a complex issue that has a number of areas that can be focused upon for

improvement in human health. There remains a lot left to be done in research and practice, and

as dengue becomes a larger threat focusing on control and development of methods and research

into DENV will become increasingly important.

A. BLOOD SAFETY AND DONOR RETENTION

One area that will always need a constant amount of focus and attention will be in

maintaining the safety and security of our blood supply. Without a stable blood supply surgical

and medical procedures simply cannot be done, and communities should not have to worry if a

unit of blood is harmful or helpful. Therefore research into more efficient screening assays, and

improving our pre-donation screening for deferrals will always be a challenge that has room for

expansion as blood collection systems try to achieve 100% efficiency from donors.

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B. COMMUNICATIONS

From a risk communications standpoint for dengue control and management it is

important that a constant upkeep of strategies be maintained. Particularly, in areas where dengue

is at an endemic level a need for constant communication between agencies, healthcare

professionals, and the community should be maintained. Communication methods also need to

improve the blood collection process. Deferrals send an extremely negative message to an

individual especially when it comes to donating a product that is always in demand and can save

a life. Pre-donation screening should always try to find new ways to communicate better in

order to better donor retention rates to eliminate blood shortages. Additionally, communication

messages need to be developed for the outreach of blood collection services to viable donors and

continued efforts should be made to ensure donor retention after DENV infection has been

cleared.

C. VECTOR AND PATHOGEN CONTROL

There will also be a further need to understand vector biology, in order to eliminate

contact between vectors and human populations. Proper analysis and review of methods should

always be factored into an integrated vector management strategy and these results should

always be reported to the community and general public so that feedback can be utilized to

develop more cohesive strategies. Additionally, research into vaccination development needs to

find ways to account for the potential of new viral serotypes developing in the sylvatic cycle of

non-human primates. An inflexible vaccine could potentially cause more harm then good if it

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does not adequately protect, and as a result primes a population for a hger number of DHF or

DSS cases.

IV. CONCLUSIONS

There is a real need for the United States to begin preparations for outbreaks of DENV.

Among these preparations drafting of communication messages for communities will be crucial

for reducing the impacts any outbreak may have. In particular, ensuring that communities are

educated on mosquito vector control could eliminate many vector habitats and halt the

transmission cycle. Further-more, the ability to plan in advance will allow for the establishment

of appropriate communication channels between blood collection services and oversight

agencies, creating a unified message for the public with minimal inconsistencies. There should

also be efforts placed into developing ways to evaluate planned communication messages. In the

case of an outbreak it will be extremely useful to understand what messages achieved the desired

goals and where improvements need to be made for future outbreaks.

The creation of efficient DENV assays for blood collection services must be undertaken.

Development before an outbreak allows for appropriate quality control measures to be

implemented ensuring the safety of the blood supply, which can eliminate of mental noise from

an outbreak scenario. This would allow for efforts to be spent addressing other major concerns

of communities during outbreaks.

Finally, monitoring and investigation into the development of new serotypes should be

undertaken. Likewise, as monitoring occurs vaccine development needs to continue. With

appropriate monitoring vaccine development will be able to address new serotypes and

incorporate them into research strategies to provide protection to all serotypes of DENV.

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