Dengue: the day the fever breaks is the dangerous one

Every year from about August through November, a version of the same conversation happens in this clinic several times a day. Someone has had a high fever for three days, body aches that feel as though they are coming from inside the bones, and a headache sitting behind the eyes. They want to know whether it is dengue, and they want to know what the platelet count is.

Both are fair questions, and neither is the one that decides how this ends. The question that matters is: what day of the illness is this, and what is happening now that the fever is settling?

How dengue actually runs

Dengue is not one illness that gets steadily worse and then steadily better. It runs in three phases, and the risk is not spread evenly across them.

1. Febrile phase, roughly days one to three. High fever, severe headache, pain behind the eyes, deep muscle and joint pain, sometimes a flushed rash. The patient feels dreadful. This phase looks the worst and is usually the least dangerous.
2. Critical phase, roughly days four to six, beginning as the fever comes down. In most people nothing happens and recovery simply starts. In a minority, small blood vessels begin leaking plasma for twenty-four to forty-eight hours. This is the phase in which dengue harms people.
3. Recovery phase, from about day seven. Appetite returns, energy comes back over a week or two, and an itchy rash on the palms and soles is common and harmless.

So a falling temperature on day four is not automatically good news. It is the signal to pay closer attention, not less.

“The families who get into trouble are almost never the ones who panicked on day two. They are the ones who relaxed on day five.”

What to watch for at home

The warning signs below are the ones the World Health Organization groups together for exactly this purpose. Any single one of them means the person should be assessed the same day, not tomorrow morning.

• Severe or constant abdominal pain, or pain when you press the upper right side of the belly
• Persistent vomiting — three or more episodes in an hour, or an inability to keep fluids down
• Bleeding from the gums or nose, blood in vomit or stool, or unusually heavy menstrual bleeding
• New restlessness, drowsiness or confusion, or a child who has gone quiet and floppy
• Passing much less urine than usual — for an adult, nothing for six to eight hours
• Cold, clammy hands and feet with a fast pulse, or feeling faint on standing

Fluids matter more than anything else you will do

Plasma leak is a volume problem, and volume is something a family can start correcting at home hours before anyone reaches a hospital. For an adult with dengue, aim for a steady intake through the day of oral rehydration solution, rice water, soup, lassi, coconut water or plain water — sipped continuously rather than drunk in large amounts at once, which usually comes straight back up.

The measure that tells you it is working is not how much went in. It is urine: pale, and passed at least every four to six hours. Dark urine, or long gaps between, means the intake is not keeping up.

Painkillers: paracetamol, and nothing else

Use paracetamol for the fever and the aches, at the dose printed for the person's weight, properly spaced. Do not use aspirin, ibuprofen, diclofenac, mefenamic acid, or any of the combination sachets sold for flu — they interfere with platelets and irritate the stomach lining at precisely the moment dengue is already making bleeding more likely.

This matters more than it sounds. A meaningful share of the dengue bleeding we see has been made worse by a painkiller bought over the counter by a family trying to help.

About the platelet count

Platelets fall in almost all dengue, and the fall is expected rather than alarming in itself. What we track is the trend across days, alongside the haematocrit — a rising haematocrit with a falling platelet count is the fingerprint of plasma leaving the circulation, and it is that combination, not a platelet number on its own, that tells us someone needs admission.

Platelet transfusion is not given to correct a number. It is given for bleeding, or at a threshold far lower than most people expect. If a transfusion is offered purely because a figure crossed a line, it is reasonable to ask for a second opinion first.

Stopping the next one

The mosquito that carries dengue bites in daylight, breeds in clean standing water, and rarely travels more than a couple of hundred metres in its life. That last fact is the useful one: if there is dengue in your house, the mosquito that caused it almost certainly bred within sight of your door.

• Empty and scrub — not merely tip out — water coolers, plant trays, pet bowls and buckets twice a week
• Cover overhead and underground tanks properly, including the gap around the inlet pipe
• Clear roof gutters, and any tyres, broken pots or plastic sheeting holding rainwater in the yard
• Use repellent on exposed skin in the morning and late afternoon, when this mosquito bites
• Keep someone with dengue under a net during the day for the first week, so the mosquito that bites them does not carry it to the rest of the household

If anyone at home has had a fever for more than two days in dengue season, come and be tested rather than waiting to see. A confirmed diagnosis on day two changes nothing about the treatment — but it means that on day five, when the fever settles, you already know what you are watching for.