Dengue: Why It’s More Fatal the Second Time
Dengue is a mosquito-borne disease that is caused by a virus from the Flaviviridae family. It is popularly known as a breakdown fever and often leads to complete body shut down. Symptoms range from fever, rashes, joint, and muscle ache but it can become life-threatening, especially when left untreated.
However, if a person gets dengue for the second time, researchers claim the disease is most fatal during this stage. To understand the reason behind this, we must first understand (i) how the disease spreads and (ii) how the body reacts to it.
Transmission of Dengue
The disease spreads through an infected Aedes mosquito – a day-biting mosquito that feeds on multiple people, about 3-4 times in its lifetime thus giving it ample opportunities for the virus causing infection to be passed into the human host while the female mosquito is feeding.
The virus is called DENV and their genetic design is what makes the extent of infection and transmission so rapid. Once the virus enters the host cells, they immediately produce proteins on entering the body cells.
Upon entering the body, it takes the virus several days or a week to run its course and leave the body – passing it through the lymph nodes and bloodstream.
The virus stores and sustains itself in your white blood cells like the antibodies by binding itself into the white blood cell receptors and enters it. On entering, the virus uses the host’s antibody as a multiplication ground where it multiples in number and leaves the cell to infect other nearby cells and this process continues. Thus, the virus takes advantage of the host cell’s energy and metabolism.
Eventually, antibodies that bind to the antigen (DENV) will trigger an immune response to produce the required amount of antibodies to fight off the virus and that is how a person gets cured.
How the Body Reacts to Dengue Virus
Typically, antibodies have memories – once your immune system fights off a pathogenic disease, it remembers it for the future and the person becomes immune or unreactive to the disease during the next encounter. However, this is not the case for the dengue virus as the virus and many serotypes and mutation strains. Therefore, immunity to one serotype won’t protect you from the other.
In fact, if a person contracts the virus again by another serotype, the immunity to one serotype can enhance the infection and symptoms. This is why contracting dengue the second time is even more dangerous than the first.
Worse symptoms the second time, Credit: piqsel
What Happens the Second Time
Think of it as the immune system getting stimulated during the second disease; the memory that antibodies produced is not a great match to the mutated virus and does more harm than good.
This causes an out of control or undesired immune response that eventually causes hemorrhagic fever which could further progress to shock syndrome, a condition where the heart is unable to pump or contract efficiently.
The antibody may recognize the different serotype virus the second time but not well enough. As a result, it is unable to clear the virus from the system. Ironically, its attempt to bind and neutralize the virus does more harm. This is because the binding “lock and key” mechanism is not a perfect fit for the other serotype and the antibody is technically helping the virus to invade, spread and multiply in the immune system and body cells.