Dengue: the fever with a dangerous second phase

What it is, in plain words

Dengue is a viral infection spread by day-biting Aedes mosquitoes. Most infections are mild. The critical period is not when the fever peaks but when it drops, around day three to seven, because plasma can then leak out of the blood vessels and platelets fall.

Signs to look out for

• Sudden high fever with severe headache and pain behind the eyes
• Intense muscle and joint pain, which gave it the name breakbone fever
• Nausea, vomiting, and a widespread red rash
• Mild bleeding: nose, gums, easy bruising
• Warning signs as fever settles: severe abdominal pain, persistent vomiting, restlessness, cold clammy skin, bleeding

Why it happens

Four virus types circulate. A second infection with a different type carries a higher risk of severe dengue, which is why residents of endemic areas and repeat travellers need particular care.

How doctors confirm it

NS1 antigen and PCR confirm early infection; IgM antibodies become useful later. Daily full blood count monitors falling platelets and rising haematocrit, the marker of plasma leakage.

Treatments and solutions

• Paracetamol only for fever and pain, and strict avoidance of aspirin and anti-inflammatory drugs, which increase bleeding
• Generous oral fluids, with monitoring of urine output
• Daily medical review during the critical phase in anyone with risk factors
• Hospital admission and carefully titrated intravenous fluids for warning signs
• Mosquito bite prevention during illness, so household mosquitoes do not transmit it further

Living with it day to day

Prevention is bite avoidance during the day: repellents, long sleeves, screens and removing standing water around the home. A vaccine exists for specific situations and previous infection status.

When to seek medical help

Return to hospital immediately if severe abdominal pain, repeated vomiting, bleeding, extreme lethargy or cold extremities appear as the fever falls.

This article explains general health information in simple language. It does not replace advice from your own doctor.