Every monsoon, fever cases rise sharply across India. Dengue, malaria and chikungunya are among the most common concerns, but in the first few days they can look very similar.

High fever, chills, weaknesses, headache, body pain and joint pain can occur in all three. This is why symptoms alone are often not enough to make the diagnosis.

The important point is not to wait for several days before testing. The test simply needs to be chosen according to the day of fever.

Dengue: NS1, PCR or IgM?

During the first week of illness, dengue is best detected using the NS1 antigen test or dengue RT-PCR.

PCR detects the genetic material of the virus and is particularly useful early in the illness. NS1 also detects an active infection and is commonly used during the acute phase.

The Dengue IgM antibody test becomes more useful after about five to seven days, once the body has had time to produce antibodies.

An IgM test done too early may be negative even when the patient has dengue. Similarly, a negative NS1 or PCR result later in the illness may not completely exclude it.

A complete blood count is useful for monitoring platelets, white-cell counts and haematocrit, but platelet count alone cannot diagnose dengue.

Patients should not panic solely because platelets are falling. The overall clinical condition, hydration, bleeding, blood pressure and haematocrit are equally important. A rising Immature Platelet Fraction (IPF) may suggest bone-marrow platelet recovery but should not be used alone for clinical decisions.

Aspirin, ibuprofen and similar painkillers should be avoided when dengue is suspected because they can increase the risk of bleeding. Paracetamol is generally preferred.

Chikungunya: PCR Is Best Early

Chikungunya typically causes severe joint pain, sometimes with stiffness or swelling. In some patients, the joint pain can continue for weeks or even months.

During the first week of illness, Chikungunya RT-PCR is the most useful test because it directly detects the virus.

After approximately one week, the Chikungunya IgM antibody test becomes more useful.

Again, timing matters. An antibody test done very early may be falsely negative, while an IgM result may remain positive for some time after the acute infection has passed.

Malaria: Test Immediately

Malaria should be tested for as soon as it is suspected.

The usual first-line tests are a peripheral blood smear and a rapid malaria antigen test. A blood smear can also help identify the malaria species and estimate the parasite load.

One negative test does not always rule out malaria. Parasite levels may be low or fluctuate, particularly early in the illness. If the patient continues to have fever with chills and malaria remains strongly suspected, the smear may need to be repeated.

Malaria PCR can be useful for detecting low parasite levels or confirming the exact species, but it should not delay immediate smear or antigen testing in an acutely ill patient.

Do Not Start Treatment Based Only on Symptoms

Malaria requires specific antimalarial medicines. Dengue and chikungunya are viral infections and are mainly managed with hydration, fever control and monitoring.

Self-medicating with leftover antibiotics does not treat dengue or chikungunya.

Unnecessary antibiotics may cause side effects, affect the kidneys or liver and contribute to antibiotic resistance.

Similarly, patients should not start antimalarial medicines simply because they have fever and chills. Laboratory confirmation is important wherever possible.

Who Should Not Wait?

Some patients can deteriorate faster and require earlier medical assessment.

This includes infants, young children, pregnant women, elderly patients and people with diabetes, kidney disease, heart disease, cancer or reduced immunity.

Older patients may not always develop a very high fever. Sudden confusion, weakness, poor appetite, drowsiness or reduced urine output may be the main warning signs.

Urgent medical attention is required if there is persistent vomiting, severe abdominal pain, bleeding, breathlessness, fainting, confusion, seizures, reduced urine output or sudden worsening as the fever begins to settle.

The Role of PCR-Based Fever Testing

PCR testing is particularly valuable during the early stage of infection, when antibodies may not yet be detectable.

It can also help when several infections appear possible, routine tests are negative despite strong clinical suspicion, or mixed infections need to be ruled out.

The key message is simple: do not diagnose monsoon fever from symptoms alone. Test early, choose the correct test for the correct day, and interpret the result along with the patient's clinical condition.

Key Takeaways

  • Dengue: NS1 antigen or RT-PCR is most useful in the first week; IgM becomes more useful from about day 5-7. Monitor the patient, haematocrit and platelet trend; IPF is supportive, not a standalone decision tool.
  • Chikungunya: RT-PCR is most useful in the first week and IgM later. Severe joint pain may continue even after the fever resolves.
  • Malaria: Test immediately with a peripheral smear and/or rapid antigen test. Repeat the smear if suspicion persists; PCR is supplementary and should not delay initial testing.

(Dr Ajay Phadke, Director, Strategic Business Development, Agilus Diagnostics)



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