Nicknamed “break-bone fever” for its severe muscle aches and fevers, dengue is the fastest-spreading, mosquito-borne disease in the world. The World Health Organization (WHO) estimates 50 – 100 million people are infected annually, with half a million hospitalized with Dengue Hemorrhagic Fever (DHF). Seasoned travelers will be familiar with Dengue, as the disease is prolific in tropical and subtropical countries in Asia and Latin America.
Part of the Flavivirus group, dengue is divided into four serotypes, numbered 1 – 4. When a person is infected with dengue for the first time, the patient suffers the typical “dengue-like” symptoms. All four strains can be present in the same geographic area, at the same time.
The real risk begins when the same person gets infected again, with a different strain of dengue. This is what leads to a more severe illness and progression to DHF, where mortality rates can reach 50%. The third time a person gets Dengue… well, you get the picture. Unfortunately, the first Dengue infection frequently goes unnoticed or is attributed to an “influenza-like” virus.
Symptoms of Dengue include muscular aches and pains, fevers, headache, nausea, vomiting and often is accompanied by a fine petechial or “pinpoint” rash. Severe cases can progress to DHF where the victim suffers from massive bleeding, frequently from IV sites, gums, and rectum. People generally progress to DHF when they have been previously infected by Dengue, earlier in their life.
Basically, the more times you get Dengue, the greater your risk of death. The concept that multiple, subsequent infections of Dengue lead to a worse disease is exactly the difficulty vaccine researchers are dealing with.
Researchers are still not sure what causes the second infection of Dengue to be more severe, but it appears confusion of the immune system is to blame. When the body encounters something foreign and deemed a threat, like a virus, it produces antibodies to attack the invader. These antibodies often travel with white blood cells riding alongside, ready to attack the virus, bacteria, etc.
When Dengue Virus is first encountered by the immune system, this is exactly what happens and the body generally defends itself well. A few copies of the successful antibody are then stored, in case the body runs into that same virus again. When the second and different strain of Dengue is encountered, the antibodies and white blood cells go to attack. However, this new virus is just a little bit different, and the antibody has trouble attaching properly. Unfortunately, the antibody can attach just well enough to allow the virus access to its white blood cell passenger, introducing the virus to a whole new type of cell and a great opportunity to rapidly reproduce.
Treatment for Dengue Fever is based upon the symptoms and making the patient comfortable. If doctors vaccinate a person against dengue, are they increasing the patient’s chances of going right to DHF and skipping their first infection? This is why researchers are not yet producing a vaccine for the public, yet.
A vaccine was developed in 2015, and the Philippines rolled out a Dengue vaccination program in 2016, however, there are still issues to overcome with the vaccine in terms of side effects. The vaccine’s manufacturer publicly warned government health authorities across the world that the vaccine would induce severe hemorrhagic for anyone who was immunized and had not contracted Dengue previously. The Philippines government then ceased the program.
Presently, there is no publicly available safe vaccine so mosquito control and bite prevention are the only methods to prevent dengue.
The WHO estimates that there are 2.5 billion people living in areas at risk. That’s approximately 40% of the world’s population. In 1970, there were only nine countries with Dengue Fever, and that list has grown to more than 100 countries. With the Aedes mosquito acting as the vector or carrying agent, it’s easy to see the explosive growth the mosquito species has had and its success in spreading the disease.
Researchers are attempting to link increased global temperatures and rainfall with the increased dengue activity. The idea that warmer weather leads to increased mosquitoes and mosquito breeding grounds are nothing new, especially combined with standing water which allows the mosquitoes to have an ideal breeding ground.
The best way to avoid Dengue Fever is to not get bitten by mosquitoes. Use a multi-step approach of using a mosquito net, if sleeping outdoors or with open windows, applying insect repellent to the skin, and wearing permeation-treated clothing and long sleeves and pants when outdoors.
Avoid areas with standing water such as upturned canisters, flower pots, tires that may contain water and lakes or large puddles. Public health campaigns focus on the destruction of these standing water breeding grounds and implementing proper water storage options to at least try to eliminate or decrease the Aedes mosquito population.
Travelers headed to areas with Dengue Fever activity should travel prepared. Caution should also be used when looking at the time of year, especially during rainy seasons. Dengue is not be going away anytime soon and savvy travelers need to be aware of it and start getting used to taking proper precautions.