Dengue Fever: When And How To Get Tested?
Dengue fever is a viral infection transmitted to humans by mosquitoes that live in tropical and subtropical climates and carry the virus. Blood testing detects the dengue virus or antibodies produced in response to dengue infection.
Dengue is a mosquito-borne viral infection which can cause a severe flu-like illness. The infection spreads through the bite of infected Aedes mosquitoes (Ae. aegypti or Ae. albopictus). There are 4 Dengue virus strains (DEN 1, DEN2, DEN3, and DEN4) commonly associated with dengue infection. Among these, DEN 2 is more commonly associated with outbreaks.
As there has been a sudden rise in the cases of Dengue infection these days, here is a quick guide to know the symptoms and to prevent transmission of the virus. This guide will also help to identify what and when to get tested if you suspect dengue-like symptoms.
What causes dengue fever?
Dengue fever is caused by one of four dengue viruses. When a mosquito infected with the dengue virus bites you, the virus can enter your blood and make copies of itself. The virus itself and your immune system’s response can make you feel sick.
The virus can destroy parts of your blood that form clots and give structure to your blood vessels. This, along with certain chemicals that your immune system creates, can make your blood leak out of your vessels and cause internal bleeding. This leads to the life-threatening symptoms of severe dengue.
Signs & Symptoms Of Dengue
The symptoms of dengue usually appear 4-10 days after being bitten by an infected mosquito. The most common symptoms associated with dengue fever may include:
– Fever as high as 104℉ or 40℃
– Severe headache
– Eye pain, typically behind the eyes (Retro-orbital pain)
– Muscle, bone, or joint pain
– Rash
– Nausea and vomiting
– Loose motions
– Decreased appetite
– Weakness
– Swollen glands
When is it ordered?
Testing may be ordered when individuals have signs and symptoms associated with dengue following travel to tropical locations where the dengue virus is present. Some of the main signs and symptoms include:
- Sudden high fever (104°F or 40°C)
- Severe headache or pain behind the eyes
- Joint, muscle and/or bone pain
- Gum and nose bleeds
- Easy bruising
- Low white blood cell count
Molecular testing is ordered within one week of the onset of symptoms to detect an acute infection, while antibody testing may be ordered more than 4 days after symptoms appear. If antibody testing is performed, an additional blood sample may be collected after two weeks of symptoms to determine if the antibody level is rising.
How To Diagnose Dengue?
A blood test is generally advised if a person is down with fever, muscle pain, and weakness or has any other symptoms of dengue. A lab test is the only way to confirm dengue infection. However, the type of Dengue test may depend on the time of infection and the appearance of the symptoms of dengue fever. Therefore, before you consider a blood test for dengue, you must know about the different types of blood tests available.
Dengue testing is divided into 2 categories:
- A) Direct Tests: Tests identifying the virus by antigen / genetic signature. These include a nonstructural protein 1 (NS1) antigen test done through ELISA, and a dengue PCR test done using RT-PCR technique. These tests are 99-100% specific with the latter having higher sensitivity.
- B) Indirect Tests: Tests related to the body’s response against the virus. These include IgM and IgG antibodies against Dengue virus measured by ELISA technique.
Here is a quick read which can guide you about the different tests suggested to identify dengue infection.
- A) Direct Tests
Dengue RT-PCR test
This test is also used to detect dengue virus in the early course (first 5 to 7 days) of the infection. It detects the viral genome (the genetic material of the virus) in the blood. This test is around 90% sensitive and 95% specific against the infection. This is the most sensitive and specific test suggested to be taken in the initial phase of the infection.
The dengue PCR test should be done within 5 days after the symptoms start to appear.
