Dengue Fever: When And How To Get Tested?

In India, millions of people get dengue every year, especially during monsoon season. Since its symptoms—like fever, headache, and body pain—are similar to other illnesses, a blood test is the only way to confirm it. Doctors use different tests based on how long you’ve been sick. The NS1 Antigen and PCR tests detect the virus in the first few days, while the IgM and IgG antibody tests show if your body is fighting or has fought dengue before. A CBC test checks platelet count, which can drop in dengue cases. Early testing helps in proper treatment and prevents serious complications. If you have a fever, don’t ignore it—get to know how to interpret dengue test!
 

Understanding dengue

Dengue, or break-bone fever, is a mosquito-borne viral infection prevalent in tropical and subtropical regions. While many infected individuals remain asymptomatic, common symptoms include high fever, headache, body aches, nausea, and rash. Most patients recover within 1-2 weeks, but severe cases may require hospitalisation and can be fatal. Reducing mosquito exposure, particularly during daylight hours, can lower the risk of infection. Treatment primarily involves pain management, as no specific cure currently exists.
 

Aetiology

Four distinct dengue virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4) cause the disease. Infection occurs through the bite of a female Aedes aegypti mosquito carrying any of these serotypes. In rare instances, the Aedes albopictus (Stegomyia albopicta) mosquito may also transmit the virus.
 

Transmission

Dengue fever spreads from person to person via bites from Aedes aegypti mosquitoes. A healthy mosquito becomes infected by feeding on the blood of an infected individual and subsequently transmits the virus to others through subsequent blood meals. Infected individuals can transmit the disease to mosquitoes for 4-5 days (up to 7 days) following the onset of infection.
 

Aedes Aegypti Mosquito

• This dark mosquito features white bracelet-like markings on its legs and white spots on its body.
• The mosquito is not the primary cause of the disease but serves as a vector, transporting the virus between individuals.
• The incubation period spans 8 to 12 days, during which the virus multiplies in the mosquito's digestive system and settles in its salivary glands. The mosquito then becomes capable of transmitting the disease for the remainder of its life.
• Mosquito bites are most frequent in the early morning and before sunset.
• Each time a female mosquito requires nourishment, it may bite multiple individuals.
 

Incubation Period

The onset of symptoms occurs 4-10 days after an infected mosquito bite.

Symptoms

The illness presents as severe flu-like symptoms and is considered when fever exceeds 40° C, along with at least two of these indicators:
• Intense headache.
• Retroorbital pain.
• Muscle and joint discomfort.
• Queasiness.
• Emesis.
• Skin eruptions.

Symptom duration typically ranges from 2 to 7 days.
 

Identifying Dengue: Diagnostic Methods

A blood examination is typically recommended when an individual experiences fever, muscle soreness, fatigue, or other dengue-related symptoms. Laboratory analysis remains the sole definitive method for confirming a dengue infection. The specific test employed may vary based on the duration of the infection and the onset of dengue fever symptoms. Thus, it's crucial to understand the various blood tests available before pursuing dengue diagnostics.
 

Dengue detection methods fall into two main categories:

A) Direct detection: These tests identify the virus through its antigen or genetic material. They include the nonstructural protein 1 (NS1) antigen test using ELISA and the dengue PCR test utilising RT-PCR technology. Both tests boast 99-100% specificity, demonstrating higher sensitivity.

B) Indirect detection: These tests assess the body's immune response to the virus. They involve measuring IgM and IgG antibodies against the dengue virus using ELISA methodology.

Here’s a brief overview that can assist you in understanding the various tests recommended for diagnosing dengue infection.
 

A) Direct Tests

1. Dengue NS1 Antigen

This test is conducted during the early stages of infection, typically within the first five days after symptoms begin. The NS1 antigen is detectable from the first day of dengue infection and can remain present for 5-7 days. After this period, it starts to decrease in the body, which may lead to false-negative results.

2. Dengue RT-PCR test

This test also identifies the dengue virus in its early phase (within the first 5 to 7 days) of infection. It identifies the viral genome (the virus's genetic material) present in the blood. This test exhibits approximately 90% sensitivity and 95% specificity regarding the infection. It is considered the most sensitive and specific test recommended during the initial stages of disease. 

The dengue PCR test should be performed within five days after the onset of symptoms.
 

B) Indirect Tests

1. Immunoglobulin M (IgM) test for Dengue

This test identifies IgM (antibodies) in the bloodstream, which emerges in the early phase of the disease and indicates an acute or recent infection. A dengue antibody IgM test should be performed if dengue symptoms persist for more than five days. This test is generally conducted after the fourth day following the onset of symptoms since antibodies begin to develop after 4-5 days of infection. 

Note:- During the first week after symptoms appear, dengue PCR tests and NS1 antigen tests are advised.

A combination of NS1 antigen/PCR and IgM antibodies is recommended between the third and ninth days.

2. Immunoglobulin G (IgG) test for Dengue

This test is utilised to determine infection in the later stages of the disease, as the levels of IgG monitored in this test tend to rise gradually. Generally, IgG antibodies can be detected in low amounts starting around 14-21 days after infection, after which they progressively increase. These antibodies may remain in the bloodstream for about 90 days and, in some instances, may persist for a lifetime.

You can have an IgG antibody test for dengue after 14-21 days post-infection or even later since these antibodies linger in the blood for several months following infection. IgG antibodies indicate a previous infection, recovery from dengue, or post-vaccination against dengue.

3. Complete Blood Count (CBC)

Dengue is often linked to a reduced platelet count (normal platelet counts range from 1.5 to 4 lacs). Therefore, platelet counts must be monitored carefully and regularly once the fever subsides. 

If a patient tests positive for dengue-specific antigen, a decline in platelet count and a drop in total white blood cells (WBC) count may be evident. However, it is crucial to understand that the diagnosis of dengue does not rely solely on platelet counts.

The laboratory tests mentioned above can aid in diagnosing and confirming dengue fever. Nevertheless, some of these tests can overlook a diagnosis in specific individuals if conducted outside the specified timeframe of illness. While the Dengue RT-PCR test remains the most sensitive and specific for dengue, a combination of NS1 antigen and IgM can also be beneficial in identifying early infections.
 

Clinical Diagnosis

Residence or travel within the past 14 days to an endemic region, plus fever and two of the following:

Warning Indicators

• Severe, persistent abdominal discomfort or tenderness.
• Recurrent vomiting (≥3 episodes in 1 hr or ≥4 in 6 hrs).
• Accumulation of fluids (pleural effusion, ascites, or pericardial effusion).
• Bleeding from mucous membranes (gums, nose, vagina [metrorrhagia or hypermenorrhea], kidney [macroscopic hematuria]).
• Changes in mental state (irritability, drowsiness, Glasgow Coma Scale score <15).
• Enlarged liver (≥2cm below costal margin).
• Increasing hematocrit (in at least two consecutive measurements taken 6 hours apart).

Classification of Dengue Cases

No warning indicators

For patients exhibiting warning signs of severe dengue OR any of the following:
• Pregnancy.
• Acute renal failure.
• Coagulopathy.
• Dyspnea.
• Inability to tolerate oral fluids.
• Co-existing conditions and social risk on a case-by-case basis.
 

Severe Cases

For patients with any of the following:
• Shock or respiratory distress due to plasma leakage.
• Clinically significant bleeding.
• Severe organ impairment (myocarditis, hepatitis [ALT or AST>1000 IU] encephalitis).
 

Group A - Outpatient care.
Group B - Inpatient care.
Group C - Inpatient care.
 

Treatment

No specific medications exist for dengue fever, making prevention crucial. Infected individuals are advised to:
• Rest adequately.
• Maintain hydration.
• Use pain relievers.
• Avoid anticoagulants, such as Aspirin.
• Prevent mosquito bites to limit disease transmission.

Medical intervention and fluid replacement may help curb disease progression and save lives in severe cases.
 

Prevention

• Some countries have approved a vaccine for individuals aged 9-45 living in endemic areas.
• Controlling Aedes aegypti mosquitoes is key to preventing dengue fever.
• The most effective prevention involves avoiding mosquito bites by:

• Eliminating breeding sites, including indoor and outdoor water containers.
• Weekly maintenance of water storage units: covering, replacing, and cleaning, including flower vases.
• Applying insect repellent creams indoors and outdoors.
• Wearing long-sleeved clothing.
• Ensuring window screens are intact.
   

Dengue Management DO’s and DON’Ts

❌ AVOID using corticosteroids routinely. They are not commonly recommended and can increase the likelihood of gastrointestinal bleeding, high random blood sugar test, and immune system suppression.
❌ AVOID giving prophylactic platelet transfusions or transfusions for low platelet counts. Platelet transfusions do not lower the risk of severe bleeding and may lead to fluid overload and extended hospitalisation.
❌ AVOID administering half normal (0.45%) saline. It leaks into third spaces and can exacerbate ascites and pleural or pericardial effusions.
❌ AVOID assuming that intravenous (IV) fluids are essential. First, determine whether the patient can ingest fluids orally. Utilise only the minimal IV fluid needed to perfuse the patient adequately. Reduce the IV fluid rate as the hemodynamic status improves or urine output increases.

✅ DO inform outpatients when they should return. Educate them on warning signs, their timing, and the critical phase following defervescence.
✅ DO acknowledge the critical phase. This crucial phase commences with defervescence or a rising hematocrit and lasts 24-48 hours. During this stage, some patients may deteriorate within hours and will require close observation.
✅ DO meticulously monitor fluid intake, output, vital signs, and hematocrit levels. As detailed in the treatment algorithms, intake and output should be observed based on hemodynamic status and the severity of the clinical presentation.
✅ DO identify and address early shock. Early shock (also referred to as compensated or normotensive shock) is marked by a narrowing pulse pressure (systolic minus diastolic BP < 20 mmHg), an elevated heart rate, and delayed capillary refill or cool extremities.
✅ DO administer colloids (such as albumin) for refractory shock. If patients do not respond to 2–3 boluses of isotonic saline, they should receive colloids rather than additional saline instead.
✅ DO provide packed red blood cells (pRBCs) or whole blood for significant bleeding. If the hematocrit is declining with unstable vital signs or evident severe bleeding, blood should be transfused immediately.
 

Clinical Differentiation of Dengue, Zika, and Chikungunya

High Certainty:

• Dengue: Low platelet count, increasing hematocrit levels, decreased white blood cells.
• Chikungunya: Joint pain, skin itching.
• Zika: Skin rash, eye inflammation.
   

Moderate Certainty:

• Dengue: Reduced appetite, nausea, abdominal discomfort, shivering, bleeding tendencies.
• Chikungunya: Joint inflammation, muscle soreness, skin rash.
• Zika: Skin rash, eye inflammation.
   

Low Certainty:

• Dengue: Pain behind eyes, enlarged liver, altered taste, increased liver enzymes, positive tourniquet test.
• Chikungunya: Bleeding tendencies.
• Zika: Swollen lymph nodes, sore throat.
   

Impact of Climate on Dengue Transmission

Research increasingly demonstrates that elevated temperatures enhance mosquito breeding, accelerate larval development, and shorten the time required for mosquitoes to reach adulthood. Additionally, adult mosquitoes have been observed to feed more frequently in warmer conditions. The dengue virus multiplies more rapidly within their bodies, enabling them to infect new hosts more quickly. Warmer climates also allow mosquitoes to expand into previously cooler, non-endemic areas. Regions such as Shimla, Northern Himachal Pradesh, Jammu, and Kashmir have experienced an uptick in dengue cases. Elevated humidity facilitates mosquito survival and egg development, while excessive rainfall and flooding create ideal breeding conditions in stagnant water pools. Even drought can contribute to mosquito proliferation, as container water provides additional breeding sites.
 

Conclusion

Dengue remains a significant health concern, especially during monsoon season, and early detection is crucial for effective management. Since its symptoms can mimic other illnesses, timely and accurate testing is essential to confirm the infection and prevent complications. With TruePal’s at-home health checkup service, you can get tested for dengue from your home, ensuring quick diagnosis and peace of mind. No extended hospital waits, no hassle—just reliable results when you need them the most. If you’re experiencing symptoms, don’t delay—book your dengue test with TruePal today!
 

FAQs

1. What is a CBC test for dengue?

A CBC in dengue helps follow the course of the disease, but it will only be used to make missed or delayed diagnoses because it does not prove the presence of the dengue virus. It simply calls attention to variations in blood parameters that occur during an illness.

2. What are the seven warning signs of dengue?

• Warning Signs: Abdominal ache or tenderness.
• persistent vomiting.
• Clinical fluid buildup.
• Mucosal bleeding.
• Lethargic or restless.
• Liver enlargement exceeds 2 cm.
• Laboratory findings show that HCT is growing while platelet count is rapidly decreasing.

3. What is tested in dengue?

Laboratory diagnosis methods for verifying dengue virus infection may include virus detection, viral nucleic acid analysis, antigen or antibody testing, or a combination of these approaches. The virus can be found in serum, plasma, circulating blood cells, and other organs for 4-5 days after the sickness begins.