Health officials in Tamil Nadu's four northern districts, Vellore, Ranipet, Tiruvannamalai and Tirupattur, have stepped up surveillance after a rise in dengue cases. Ranipet has recorded 59 cases since September 1, the highest among the four districts, including 14 fresh cases between September 14 and 20. Officials said the district has recently been seeing two to four cases a day, however, the increase is not considered unusual for the monsoon period. Vellore has reported 10 cases this month, after 15 in August. Tiruvannamalai has reported around 22 cases and Tirupattur around 38 cases.

These numbers have prompted continued monitoring, inspections and mosquito-control measures. In Vellore, college hostels are being inspected, while fogging, domestic breeding checks and chlorination are being carried out. According to a report in The New Indian Express, Vellore DHO Dr M Vijay Chandran said, "Since most of our neighbouring districts, including Tiruvannamalai, Tirupattur, and Kancheepuram, are reporting a high number of dengue cases, we are also maintaining strict vigil. We have started inspection of college hostels. Intensive fogging by domestic breeding checkers and chlorination are being carried out. Further, we are monitoring all kinds of fever and segregating patients with dengue, leptospirosis, scrub typhus, and chikungunya."

Health officials have urged people not to panic but to seek medical evaluation early rather than simply taking medicines to bring down fever.

Why Can Dengue Become Dangerous After Fever Drops?

Dengue causes a very high fever. Along with that, the patient may also have headache, pain behind the eyes, muscle and joint pain, nausea, vomiting and sometimes a rash. However, the illness does not always get better when the temperature falls.

The World Health Organization (WHO) says that the critical phase usually happens when the fever comes down, often between days 3 and 7. This critical period can last about 24-48 hours. This happens because some patients can develop increased leakage from small blood vessels, known as capillary or plasma leakage. As plasma moves out of the bloodstream, the circulating blood volume can fall. In severe cases, this can lead to shock, fluid accumulation, bleeding or organ problems. The Centres for Disease Control and Prevention (CDC) says that severe dengue can develop within hours after the fever disappears. Therefore, when the fever comes down, one should not take it as proof that the danger has passed.

What Warning Signs Should You Watch For?

The 24-48 hours after the fever goes away are particularly important. Urgent medical attention is extremely important if a person with suspected or confirmed dengue develops:

  • Severe or persistent abdominal pain or tenderness
  • Repeated vomiting, particularly three or more times in 24 hours
  • Bleeding from the nose or gums
  • Blood in vomit or stool
  • Extreme tiredness, restlessness or irritability
  • Rapid breathing or difficulty breathing
  • Pale, cold or clammy skin
  • Extreme thirst or weakness

These signs can indicate that the disease has progressed towards severe dengue and needs prompt medical assessment.

Why Is Early Monitoring Important

Dengue symptoms can overlap with several other infections that cause fever. A blood test may be used to confirm dengue, depending on the stage of illness and clinical assessment.

Doctors may also monitor your blood counts, platelet levels and other parameters over time. A falling platelet count can occur in patients affected with dengue, but platelet numbers alone do not determine whether a patient will develop severe dengue. Changes in the patient's overall condition, signs of bleeding, blood pressure, hydration and evidence of plasma leakage are also important.

What To Do When Fever Lowers?

A patient should continue following medical advice even after their temperature returns to normal. Consuming adequate fluid is important, and patients should continue to be at rest. For fever and pain, paracetamol is generally recommended; aspirin and ibuprofen should be avoided in suspected dengue because they can increase bleeding risk.

Most people with dengue recover, but some can deteriorate rapidly during the critical phase. Families should therefore keep a close watch on symptoms for at least the first couple of days after the fever subsides.

Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.