Dengue fever virus, a mosquito-borne viral illness, used to be endemic in only nine countries throughout the world. In the last 45 years it has become endemic in 100 countries and is being noted sporadically in areas outside of its usual tropic and subtropic regions, including China and the United States.
Some 390 million people annually become ill will Dengue fever and according to World Health Organization (WHO) estimates, 3.9 billion people are vulnerable to exposure to the disease. Travelers who are infected with Dengue fever are often the source of the illness when it is found in non-endemic areas.
The two species of mosquitoes that spread the four types of Dengue fever viruses, are the Aedesaegypti and Aedesalbopictus are found nearly worldwide, with the Aedes albopictus having developed an ability to survive in below freezing temperatures. Due to the prevalence of the two mosquito species and their role in the transmission of Dengue fever viruses from even a single infected person, the potential exists for Dengue fever to be found in all but the most severely cold climates.
Dengue Fever Transmission
Dengue fever cannot be spread directly by person-to-person contact. It’s spread is through mosquito bites of the females of either the Aedes aegypti or Aedes albopictus species from an infected person that is then passed on to subsequent people by that mosquito carrying the Dengue virus. Each mosquito carrying the Dengue virus remains an agent of infection throughout its lifespan.
A person who has become infected through such a mosquito bite will be a possible agent of infection for usually four to five days after symptoms first appear, although this window can extend to 12 days.
Early diagnosis of Dengue fever is essential to preventing the spread of the illness by protecting the infected person from further mosquito bites that can then spread the virus to others. Such diagnosis is not always possible, depending on the area and its availability of medical care. Other times Dengue fever symptoms are so mild that they may pass almost unnoticed by the infected person.
Symptoms of Dengue Fever
Once bitten by an infected mosquito, symptoms will begin to develop within four to 10 days; such symptoms are likely to include:
Recovery from these symptoms is usually within a week. There is no specific treatment for Dengue fever, but those who are ill are advised to rest, take fluids and use acetominophen or paracetamol for fever control.
In rare instances, Dengue fever does not get better within the week and may advance to symptoms of severe or hemorrhagic Dengue. Within the first three to seven days of the onset of symptoms, fever will abate, but warning signs of this severe Dengue will begin to manifest:
Severe abdominal pain
Vomiting of blood
Bleeding of gums, and/or nose
Rapid and/or difficulty breathing
These are critical symptoms for which medical help must be sought immediately. The difference in the fatality of severe Dengue fever decreases from a 20 percent fatality rate to 1 percent fatality rate with proper medical care.
How to Avoid Dengue Fever Virus
Because exposure to Dengue fever virus requires transmission by mosquito bites, the best prevention is to avoid mosquito bites.
Use insect repellent sprays containing DEET, Picaridin or oil of lemon eucalyptus as often as needed. Apply before going outdoors, even if you don’t see any mosquitoes. The Aedesaegypti is active during daylight hours, unlike most mosquitoes who are most active during earlier and later hours.