Dengue Fever:

An Emerging Zoonotic DiseaseJ. Boren and R. L. Stanko

Department of Animal, Rangeland, and Wildlife SciencesTexas A&M University-Kingsville

Signs and Symptoms

These signs and symptoms refer to

humans, but the signs are mostly the same

for animals as well. In many cases of DF,

there are either no symptoms ,or only fever

with few or no other signs or symptoms [3].

Signs and symptoms that appear will remain

2-7 d.

In most cases:•High fever (up to 105 °F)

•Severe headache

•Rash over face or body (can disappear

quickly)

In some cases:•Low heart rate and low blood pressure

•Chills

•Muscle and bone pain

•Pain behind eyes

•Nausea and vomiting (especially in

children)

•Mild bleeding (often appears as bruising, or

as bleeding gums)

•Rapid drop in body temperature (a few days

after fever onset). A second onset of fever

may occur.

What is Dengue Fever?

Dengue fever (DF) is a virus in the Flaviviridae family and in the Flavivirus genus. It is an

“arbovirus (arthropod-borne virus)” [3]. Virus is passed on mainly through mosquito vectors in the

Aedes species and with genus aegypti. The Center for Disease Control [3] says that in rare cases,

dengue fever can be spread by blood-to-blood contact, blood transfusions, organ transplants, and from

a mother to child during birth, from an infected person to a susceptible person. There are four

“serotypes (called DENV-1-2, -3, -4)” [3] of the dengue virus. Once a person becomes infected by one

type, he or she will be protected from that strand for life, but that person is still susceptible to the other

three forms of the virus.

IntroductionThere are 50-100 million cases of dengue fever

(DF) every year world-wide with about 36 million cases with symptoms [1]. 24,000 end in death (mainly children). For more than 150 years before WWII, DF was not very common. WWII led to the spread of the mosquito vector of DF. From 1950-1970 control efforts were in place in the Americas which lessened dengue fever, but since that time, the disease has spread to much of South America and to the southern parts of North America [2]. An increase in urbanization in tropical areas and an increase in world-wide travel has further spread DF.

Dengue Hemorrhagic Fever and

Dengue Shock SyndromeDengue hemorrhagic fever (DHF) and

dengue shock syndrome (DSS) are two

severe forms of dengue fever. DF can

progress into these more extreme forms,

but it usually does not. The signs and

symptoms of DHF and DSS include those

common to DF in addition to several

others.

DHF can last 2-7 days. It consists of:

•Bleeding under the skin and from nose

and mouth

•Easy bruising

•Circulatory collapse (plasma leakage)

•Abdominal pain

•Vomiting

•Cool and clammy extremities

•Death

DSS is the most intense form of the

disease. It consists of:

•Severe abdominal pain

•Fluid/plasma leakage from blood vessels

•Heavy bleeding

•Sudden drop in blood pressure

•Death

PreventionsThe best ways to prevent the spread of

dengue fever include eliminating the

mosquito vector population by ridding an

area of containers that could house the

eggs [3], and reducing the chances of

mosquitoes biting by limiting people’s

exposure to them [5]. Wearing clothes that

cover down to wrists and ankles and

wearing socks, shoes, and mosquito

netting in an infected area can decrease the

chance of being bit. Also, using repellents

containing DEET on exposed skin and

those containing permethrin on clothing

can prevent mosquitoes from biting [5].

Another way to prevent the spread of DF

is to refrain from traveling to known

dengue-infested areas at peak seasons for

the disease.

Progression of Dengue FeverThe disease starts its transmission cycle when

an Aedes mosquito bites an infected individual.

The disease then circulates through the mosquito

and, 5-12 days later, ends up in its salivary glands

[4,5]. The incubation time (“extrinsic incubation

period”) needed in the mosquito decreases as

temperatures increase [3]. The mosquito then has

a few days or weeks (the rest of its life) to

transmit the disease to another susceptible

individual. On d 4-6 after being bit, the fever and

other symptoms begin to appear. In the less

severe forms of DF, the signs will last about one

week. Full recovery usually occurs within two

weeks. In dengue hemorrhagic fever and dengue

shock syndrome, an individual may start to

recover a few days after the initial fever onset and

then get worse. Usually the second round is when

the more severe signs and symptoms appear.

“Some [people] may feel listless, tired, and even

depressed for several weeks to months after being

infected” [5]. There is about a five-day window

when a mosquito can bite an infected person and

start the cycle over.

Who is at Risk?Dengue fever is most prevalent in tropical and subtropical

areas (because of the presence of DF vectors) [3,4].

Thus, people who live in, or travel to, these areas are most at

risk. Young children are also more likely to contract the

disease than adults. Those who have had DF before are more

likely to develop DHF and DSS during a second infection

than an individual who has never before been infected.

Weather conditions affect the population size of

mosquitoes, so it is easier to contract DF during seasons

when mosquitoes are more abundant than during seasons

where fewer mosquitoes are present.

References[1] Shepard, D.S., Coudeville, L. et al. Economic Impact of Dengue

Illness in the Americas. 2010.

[2] Gubler, D.J. Dengue and Dengue Hemorrhagic Fever. 1998. Clinical

Microbiology Reviews. 11:3. p480-96.

[3] Centers for Disease Control and Prevention. Dengue. 2010.

www.cdc.gov/dengue

[4] Cunha, J.P. Dengue Fever. MedicineNet.

[5] Mayo Clinic staff. Dengue Fever. 2010.

www.mayoclinic.com/health/dengue-fever/DS01028

Dengue fever rash. Retrieved from

http://denguefeverpictures.com/

Mosquito vector. Retrieved fromhttp://www.medanku.com/

AcknowledgementsT.B. Hairgrove, D.V.M. and P.D. Teel, Ph.D.

Funding provided by National Center for Foreign Animal and Zoonotic Disease Defense

TreatmentsThere is no cure for DF and there is not

yet a marketable vaccine [4,5]. Since it is a

virus, there are no treatments for the disease

itself, but only for the symptoms.

At-home treatments: •Drink plenty of fluids to stay hydrated

•Take drugs with acetaminophen (Tylenol)

to reduce fever and pain.

Note: Drugs containing ibuprofen should

NOT be taken, as these can lead to the

symptoms becoming worse [5].

Hospital treatments:•Fluids given through an IV

•Blood transfusions