Dengue Fever
Dengue is an arbovirus consisting of 4 serotypes (DEN 1,2,3,4) all of which can cause severe and fatal disease. After an infection with one subtype an individual will gain lifelong immunity to that subtype.
Dengue infection involves a spectrum of different symptoms, which range from a non-specific fever, classical dengue fever, dengue hemorrhagic fever, and dengue shock.

Dengue fever may begin suddenly.

There are estimated 50-100 million cases of Dengue fever/year. 250-500,000 cases of Dengue hemorrhagic fever worldwide.

Most deaths are in children 5-15 years.

Risk to travelers is estimated 1/1,000 in countries where it is present but could be worse in outbreaks.

Dengue transmission by mosquito:
Dengue is transmitted by infectious mosquitoes- Aedes egypti which is a mosquito adapted to city life and typically feeds in early morning and late afternoon.

Adults lay eggs as floating egg rafts in puddles. These mosquitoes thrive on small puddles.
Aedes egypti has a tropical and subtropical distribution.

One single mosquito will feed many times so that many people could become infected at the same time.

These mosquitoes are found active in the daytime and are found in and around human habitation.

They lay eggs in shallow containers that rainwater has collected in.

Recently the mosquito Ades albopictus has been recognized as a disease causing mosquito.

Aedes Albopictus (Asian Tiger mosquitoes) were recently introduced to Hawaii and Texas.

If the dengue virus is also introduced into these areas as well then dengue transmission could occur.

This mosquito also causes Eastern Equine Encephalitis and Cack Valley viruses, but not Yellow Fever.

Dengue infection:
Mild disease Symptoms include high fever, severe headache, and joint and muscle pain.

Nausea, vomiting and anorexia may also occur.

A rash may also appear 3-4 days after the onset of fever spreading from the torso to the arms, legs and face.
Dengue hemorrhagic fever is usually defined as having a rash, haemorrhage and fever.

Patients should be checked for evidence of bleeding, their hydration status, and their blood pressure.

Bleeding is evidenced by petechiae, purpura, increased bleeding from gums and increased menstrual flow.

The W.H.O criteria for diagnosis are:
These include fever, bleeding, platelets less than 100,000; and evidence of ' leaky capillaries'.

Co-factors that will worsen the severity of dengue include having a prior infection with one or more of the other 3 serotypes (and how long ago, and how severe); age; and host genetics.

The strain of serotype is also important with the lethality ranked: DEN 2>3>4>1.

Unusual complications of dengue are encephalopathy, liver and heart damage; and gastrointestinal bleeds.

Clinical tests for dengue fever:
CBC- WBC, Hb, and platelets; albumen, liver function tests, urinalysis (to check for hematuria), and direct tests to look for virus isolation and serology.

Blood serology should be taken during the acute phase (less than 5 days after start of fever) to check for acute serology and virus isolation; and again after 6-21 days to check for convalescent serology and confirm the diagnosis.

A rapid diagnostic test for dengue fever is at present not approved.

If the fever starts greater than 2 weeks after the end of travelling then this is not dengue fever, as dengue will present within 2 weeks.
Differential diagnosis includes influenza, rubella, measles, malaria, typhoid, leptospirosis, meningococinemia, rickettsia, bacterial sepsis, and other viral hemorrhagic illnesses.

Treatment for Dengue
Treatment of dengue hemorrhagic fever includes fluids, rest, anti-pyretics (acetaminophen but no ASA or NSAIDS), and to check blood pressure, hemoglobin and platelets.

Patients may be treated at home if there is no bleeding and well hydrated.

Observation is warranted if sicker and ICU admission if bleeding.

Serial hemoglobin and platelets are done until afebrile for 1-2 days.

Other treatments include IV fluids and avoidance of invasive procedures.

Steroids and gammaglobulin are unproven treatments.

Personal protection against Dengue:
Because there is no vaccination or specific treatment for dengue prevention is the best way of managing the possibility of dengue infection.

Use DEET 20-30%, spray clothing with permethrin, and spray insecticide over bed.

Wear long sleeved pants and shirts.

Persons may also decrease risk by spending less time in areas where dengue more frequent.

Residential areas are the most affected while industrialized or commercial areas (like beaches, forests, and tennis courts) have less Aedes mosquitoes.

Air conditioning helps remove mosquitoes.

Prevention of Dengue Fever - destroy mosquito breeding grounds by eliminating unused containers, stock small fish that will eat mosquito larvae and vaccines are being developed.

Dengue Fever Links on the internet
Center for Disease Control CDC http://www.cdc.gov/ncidod/dvbid/dengue/
Armchair Medicine (A personal testimony) http://www.armchair.com/info/spira7.html
Medline Plus http://www.nlm.nih.gov/medlineplus/ency/article/001374.htm
MedStudents.com http://www.medstudents.com.br/dip/dip3.htm