Dengue fever
Dengue is caught in one way only, from the bite of a mosquito; it does not pass from person to person.
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Medicines commonly prescribed for Dengue fever
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: TABLET, 650 mg paracetamolActive substance: paracetamolManufacturer: Laboratorios Cinfa S.A.Prescription requiredDosage form: INJECTABLE PERFUSION, 10 mg paracetamol/mlActive substance: paracetamolManufacturer: Altan Pharmaceuticals SaPrescription requiredDosage form: EFFERVESCENT TABLET, 1 g paracetamolActive substance: paracetamolManufacturer: Neuraxpharm Spain S.L.Prescription required
Dengue is caught in one way only, from the bite of a mosquito; it does not pass from person to person. Most people go through it like a very heavy bout of flu: a week of high fever, aching that seems to reach into the bones, a rash, and then a slow return of energy. But dengue should never be judged by its first few days. The dangerous moment does not come at the height of the fever, but just as the fever falls and everything appears to be improving.
Where people catch it
The virus is carried by mosquitoes of the Aedes group, and they have a habit that defeats the usual precautions: they bite in daylight, most eagerly in the hours after sunrise and before sunset. A net over the bed at night is not enough, because at night these mosquitoes are not the ones flying.
Dengue is commonest in the tropics and subtropics:
- southern and south-eastern Asia and the Indian subcontinent;
- Central and South America and the Caribbean islands;
- tropical Africa;
- the Pacific and Indian Ocean islands, and the southern edge of North America.
Europe deserves a separate mention, because the picture has changed. The Asian tiger mosquito has settled along the Mediterranean coast, and with it have come infections in people who never left home. Small outbreaks have been recorded in France, Italy, Spain, Croatia, Portugal and Madeira, and the season runs from late spring into November, which is exactly the holiday season. That is no reason to give up a summer in southern Europe, but it is a reason not to shrug off a fever that starts after a few August days by the sea.
Dengue does not travel by coughing, kissing or shared cutlery, though the virus stays in the blood for a while, which is why blood donation is deferred after a trip to an affected area; the length of that deferral differs from country to country.
How the illness starts
Symptoms appear four to ten days after the bite, rarely later. If more than two weeks have passed since you came home and you still feel well, the incubation period is over and you can put dengue out of your mind.
A great many infections go unnoticed and are only discovered later in a blood test. When symptoms do come, they arrive within hours:
- a high temperature from the outset, often close to forty degrees, with no runny nose or cough;
- a severe headache, usually across the forehead;
- a dull ache behind the eyes that worsens when you move them;
- pain in muscles, joints and bones so marked that the illness earned the old nickname of breakbone fever;
- nausea, vomiting, stomach pain and loss of appetite;
- swollen glands in the neck;
- a rash: the face and neck flush first, as if sunburnt, and towards the end of the first week small flat spots appear on the trunk and limbs with islands of untouched skin between them; they may itch and flake as they fade.
Dengue cannot be told apart from flu, malaria or a gut infection by how it feels; that needs a blood test. So any fever that begins during a trip to the tropics, or in the month after returning, means seeing a doctor the same day. The reason is not only dengue: malaria hides behind exactly the same picture, it can kill within days, and it is ruled out first. Always say where you have been and when, because without that sentence the right tests are simply not ordered.
The dangerous days begin when the fever falls
For most people it is all over within a week. In a minority, somewhere between the third and seventh day, precisely when the fever settles and a deceptive sense of relief arrives, the illness turns towards its severe form. The walls of the small blood vessels begin to leak the fluid part of the blood into the tissues, the circulating volume drops and blood pressure with it; at the same time the platelet count falls and a tendency to bleed appears. Here the counting is in hours, not days.
Warning signs during those hours:
- severe, unrelenting abdominal pain;
- vomiting that repeats again and again and makes drinking impossible;
- bleeding from the gums or nose, bruises with no injury behind them, unusually heavy menstrual bleeding;
- blood in the vomit, or black tarry stools;
- fast breathing or a sense of not getting enough air;
- weakness so profound that standing up is hard;
- restlessness and agitation, or the opposite, drowsiness and slowed responses;
- cold clammy hands and feet with pale skin;
- no urine passed for several hours.
Here is a fact few people know: severe dengue is usually the second one, not the first. The virus comes in four varieties, and having had the illness leaves lifelong protection only against the variety you had. Meeting a different one, the old antibodies do not protect but instead help the virus into the cells. So the reasoning that runs «I have had dengue already, it holds no fear for me» works exactly the other way round. Risk is also higher in young children, older people, pregnant women, anyone with weakened immunity, and people living with diabetes, asthma, high blood pressure, kidney disease or a bleeding disorder.
When to call an ambulance
Call an ambulance (across Europe the single number is 112) or go straight to the emergency department if someone with a fever after travel develops any of the signs listed above: abdominal pain, repeated vomiting, any bleeding, confusion, cold limbs, breathlessness or a faint. Nobody drives in that state.
Take the list of medicines you use, mentioning blood thinners without fail, and name the countries you visited with dates. Severe dengue responds well to treatment when the patient reaches hospital in time; all of its danger lies in delay.
What helps and what must be avoided
No medicine kills the dengue virus, so treatment means supporting the body while it deals with the infection itself:
- rest, with no work and no exertion for as long as the fever lasts;
- plenty of fluid in small sips: water, oral rehydration solution, broth; pale urine is a simple check at home;
- paracetamol for fever and pain, in the usual doses given on the packet.
What must not be done with dengue, or with dengue suspected, is to take ibuprofen, diclofenac or other anti-inflammatory painkillers, or aspirin. All of them interfere with the platelets and irritate the stomach lining, and dengue already raises the risk of bleeding. This applies at every age; children and teenagers are not given aspirin whether dengue is involved or not. If you take one of these drugs or a blood thinner regularly, do not stop it on your own initiative, but ring your doctor first. Intramuscular injections are also avoided, since they leave large painful bruises.
The severe form is treated in hospital with fluids to replace what has leaked out of the circulation, frequent checks of blood counts and blood pressure and, if needed, transfusion of blood components. Antibiotics have no effect on viruses and are of no use here.
Recovery is rarely quick. For a couple of weeks afterwards there is tiredness, poor concentration, little appetite and low mood, and hair may shed more than usual. That is part of convalescence rather than a complication, but it is not the moment to go back to sport.
Avoiding bites on the trip
The vaccine is not available to everyone in every situation, whereas protection from bites works on any journey. Aedes lives alongside people, in towns and cities, and bites in daylight, so protection has to last the whole of the daylight day.
- Put a repellent containing DEET or icaridin on exposed skin and reapply as the label says; if you use sunscreen, the sunscreen goes on first and the repellent over it.
- Wear loose, light-coloured clothing with long sleeves and long trousers; clothing and gear can be treated with permethrin products, which are never applied to skin.
- Choose accommodation with screened windows or air conditioning, and check the mesh for holes.
- Sleep under an insecticide-treated net, daytime naps included.
- Tip out standing water around the house: saucers under flowerpots, buckets, old tyres, blocked gutters, paddling pools. Aedes breeds in clean still water, often a couple of metres from your door.
Someone who is ill should also stay under a net for the first week: a mosquito that bites them carries the virus onwards.
The dengue vaccine
A dengue vaccine exists and is licensed in Europe, but it is not one of the jabs given to everyone before a holiday. What matters to know:
- the course is two doses about three months apart, so a travel clinic has to be visited well ahead, not the week before the flight;
- it is a live attenuated vaccine, so it is not given in pregnancy, during breastfeeding, or to people whose immunity is seriously weakened;
- who is advised to have it depends on whether you have had dengue before and on where and how long you are going; national advice differs between countries;
- it is not part of the routine schedule and is usually paid for privately;
- protection is not complete, so the vaccine does not release you from repellents and nets.
The sensible approach is to sit down with a doctor a month or two before a long trip and go through the whole set: dengue, hepatitis A, typhoid, rabies and malaria prevention.
Online consultation
Before a trip, a remote appointment is a good way to work out what you personally need, given your own conditions and route: which vaccines there is still time for, whether malaria prophylaxis is required, what belongs in the travel kit. During the trip and after coming home, the doctor goes through the fever with you, when it started, where you have been, what else is happening, and says which tests to arrange today and whether there is reason to go to hospital straight away. Another common subject is the tiredness that drags on after the infection and when it is safe to train again. The warning signs listed above are not assessed through a screen: those mean calling an ambulance.
This material is for information only and does not replace medical advice.
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