What is it?
Dengue fever is a disease caused by the dengue virus. It is transmitted through mosquito bite.
Symptoms begin a few days after infection, and they include a high fever, headache, vomiting, pain in muscles and joints, and a skin rash. The affected usually recover within a couple of days. Sometimes, however, dengue fever can develop into the life-threatening dengue hemorrhagic fever or dengue shock syndrome.
Each year 50 – 528 million people are infected with dengue fever, and 10 000 – 20 000 people die of it. It is mainly seen around the equator.
What causes it?
When a mosquito sucks the blood of a human infected with the dengue virus, it becomes infected too. After a while the viruses spread to the mosquito’s saliva, and from there on the mosquito can infect another humans through biting them.
What happens during it?
Viruses are essentially just protein shells filled with genetic information. They reproduce by entering a cell, and through the instructions in their genes making the cell a virus factory. When enough new viruses have been produced and they have left to infect new cells, the original cell dies.
When the dengue virus first enters the body, they start reproducing inside white blood cells while they circulate around the body. The white blood cells aren’t oblivious to this – they start producing lots of molecules such as cytokines and interferons, and the body’s reaction to these molecules are mostly what causes the fever and the pain.
In most cases this is how bad the disease ever gets. Sometimes, however, the reproduction of the viruses can get out of hand. Other organs, like the liver and the bone marrow, can be affected. During infection it is a normal reaction of the body to enlarge the holes in small blood vessels to allow white cells to get to the tissues to destroy microbes. In severe cases of dengue fever this process can go wrong – too much fluid from blood starts leaking away from the vessels, which can cause the blood pressure to drop to dangerously low levels. This can, in turn, mean that the heart is unable to pump enough blood to vital organs. The bone marrow produces platelets that are tiny cells essential to blood clotting. If the viruses infect the bone marrow, the marrow isn’t able to produce enough platelets to keep the blood clotting as it’s supposed to. This can cause life-threatening complications such as internal bleeding.
How can it be treated?
It is very important to prevent mosquito bites in order to avoid dengue fever. This can be done through wearing covering clothing, sleeping under mosquito nets, and using insect repellent. The authorities of the countries where dengue fever is prevalent should also focus on things like removing the habitats of the mosquito in question. A new vaccine is likely to come available in some countries, although it is not as effective as had been hoped.
In standard cases the treatment focuses on supporting the body’s fight against the virus. It is important to ensure that the patients get enough fluid. Normally they can just drink it, but in more severe cases the fluids might have to be given straight to the vein.