Early Signs of Dengue: How to Identify Them

Dengue is a viral infection spread by infected Aedes mosquitoes. It commonly causes high fever, headache, body pain, joint pain, and sometimes a skin rash. Most people recover with rest and fluids, but severe dengue can cause serious complications.

Dengue is a viral infection spread by the bite of an infected Aedes mosquito. There are four related dengue virus types, and infection with one does not protect you from the others.

The first sign of dengue is usually a sudden high fever, along with a severe headache, pain behind the eyes, and aching muscles and joints. Nausea, vomiting, a blotchy rash and swollen glands often follow within a day or two.

The fever rises quickly rather than gradually, and is usually high grade. Many people also notice a flushed face and reddened skin in the first day or two, before any rash appears.

About one in four people who are infected with dengue actually fall ill. The rest have no symptoms at all, or feel only mildly unwell. This is why so many infections go unnoticed.

The most commonly reported early symptoms are:

• High fever, often 40°C (104°F) or close to it
• Severe headache
• Pain behind the eyes
• Muscle, joint and bone pain, which is why dengue is sometimes called break-bone fever
• Nausea and vomiting
• Swollen glands
• A blotchy rash of flat or slightly raised spots, which can cover a large area of the body

Fever in dengue usually lasts 2 to 7 days. Most people recover in 1 to 2 weeks, though tiredness can linger for several weeks afterwards.

Dengue is a moving illness. It is not one steady set of symptoms, and the riskiest part of the illness is often not the part with the highest fever.

• Febrile phase: Day 1 up to about day 7 of fever; What you may notice: Sudden high fever, headache, pain behind the eyes, body and joint aches, nausea, vomiting, flushed face. A blotchy rash often appears after day 3 or 4

• Critical phase: Usually after day 3 or 4 of fever, lasting about 24 to 48 hours; What you may notice: Fever starts to settle, but the person may feel worse. This is the riskiest window

• Recovery phase:When it happens: After the critical phase, lasting about 2 to 3 days; What you may notice: Appetite returns, an itchy red rash may appear, and weakness slowly eases over the next week or two

The single most important thing to understand is the critical phase. The fever drops, and many people take that as a sign that they are getting better. In dengue, the opposite can be true. Plasma can leak out of the blood vessels during this window, which is when bleeding, a sharp drop in blood pressure and shock can develop.

Between 5 and 10 in every 100 people with dengue move into this critical phase. It is more common in people who have had dengue before.

Dengue is hard to spot early because the first few days look like a lot of other illnesses. A few things make it easy to get wrong:

• The rash may not be there yet. When it does appear, it usually comes after the third or fourth day of fever, over the face, neck, chest and abdomen.
• It can look exactly like flu. Headache, body ache and eye pain also happen in flu, viral fevers, typhoid, malaria and chikungunya.
• Early blood tests can be normal. A normal blood count in the first 72 hours does not rule dengue out.
• Children may show different signs. Infants and young children often have a vague fever without the classic aches.

Research in primary-care patients found that in the first 72 hours of fever, the features that point more towards dengue than another fever are nausea or vomiting, dizziness on standing up, and a lower than normal white blood cell count. These are clues, not a diagnosis, and a normal white cell count early on does not rule dengue out. A family member or neighbour with dengue, or recent time spent in an area where dengue is common, is an important clue that people often forget to mention to their doctor.

Warning signs usually appear as the fever is coming down, often between day 3 and day 7 of the illness, or about 24 to 48 hours after the fever breaks. They need urgent medical care, not a wait-and-see approach.

Get medical help immediately if you or someone in your home has:

• Severe tummy pain or tenderness
• Repeated vomiting, three or more times in 24 hours
• Bleeding gums, nose bleeds, blood in vomit or stools, unusually heavy periods, or blood in the urine
• Black, tarry stools
• Red or purple spots, or new bruising, under the skin
• Extreme tiredness, restlessness or irritability, or a sudden change in behaviour
• Dizziness or fainting when standing up
• Cold, clammy hands and feet, or pale and mottled skin
• Fast or difficult breathing
• Passing very little urine, or being unable to drink
• Extreme thirst
• Fluid collecting in the belly or chest, which your doctor may find on examination
• An enlarged liver, which your doctor will check for

One item on this list is a change your doctor will see on a blood report rather than something you can check yourself: a rising haematocrit alongside a fast fall in platelets. That is one reason your doctor may repeat your blood count from day 3 onwards.

See a doctor the same day if you have fever along with headache, body ache or nausea and you live in, or have recently travelled to, an area where dengue is common. Do not wait to see whether it settles, and do not try to diagnose yourself.

Dengue cannot be confirmed by symptoms alone. The tests used, and when they work, are:

1. NS1 antigen test, day 1 to day 5 of illness. This detects a protein the virus releases in the first few days, while it is still in the blood, which is why the NS1 test is the one to ask for early.
2. IgM antibody test, after day 5 of illness. The body's antibody response takes about a week to become detectable, so this test is used later in the illness.
3. Complete blood count, repeated. A falling white blood cell count is often the earliest change, followed by falling platelets. A rising haematocrit suggests fluid is leaking from the blood vessels.

In India, rapid diagnostic tests are treated as giving only a probable result, because their sensitivity and specificity are limited. Confirmation in the public laboratory network is done using NS1 or IgM by ELISA.

Fever lasting more than three days, or any warning sign at all, is a reason to be seen on the same day rather than at a routine appointment.

Most people with dengue get better with rest and fluids, but the first week needs watching. There is no antiviral medicine that treats dengue; care is supportive.

• Drink plenty of fluids through the day, in small sips if you feel sick. Water, ORS, coconut water, soups and juices all count.
• Rest. Do not push through work or exercise.
• Keep an eye on how much urine you pass. Passing normal amounts of pale urine is a good sign.
• Paracetamol is the only fever and pain medicine used in dengue. The dose is 10 mg per kg of body weight (10-15 mg/kg for children), given no more often than every 6 hours, and no more than 4 g in 24 hours for adults. Check the total across every product you are taking.
• Do not take ibuprofen, aspirin, diclofenac, naproxen or any other anti-inflammatory painkiller. These can cause bleeding problems in dengue.
• Check the label of any cold, flu or pain combination you already have at home. Many contain paracetamol, and some contain aspirin.
• Do not start antibiotics or steroids on your own.
• Watch closely for warning signs, even after the fever settles.
• Keep your follow-up blood tests as advised by your doctor.

Paracetamol does not lower the platelet count or the risk of severe dengue, so it is a comfort measure, not a treatment. Your doctor will confirm the amount that is right for you.

If you cannot keep fluids down, or if you are passing very little urine, that alone is a reason to go to hospital.

Most people with dengue recover fully. Some groups are at higher risk of the severe form and need closer monitoring from day 3 onwards:

• Babies and young children
• Older adults
• Pregnant women
• Anyone who has had dengue before, since a second infection with a different dengue virus type carries a higher risk
• People with diabetes, high blood pressure, heart disease or kidney disease
• People with chronic liver disease or peptic ulcer disease
• People taking long-term steroids or regular anti-inflammatory painkillers
• People with asthma or another chronic lung disease
• People who are obese

If you fall into any of these groups and you develop a fever in an area where dengue is common, mention it when you see a doctor. It changes how closely you are watched.

Dengue cases in India peak between July and November, in the months after the monsoon. Cases are reported from every state and union territory except Ladakh, and southern and western states often report cases through the year rather than in one season.

The mosquito that spreads dengue, Aedes aegypti, bites during the day, most often in the early morning and early evening. That means mosquito nets used only at night offer less protection than people expect.

Because so many infections are mild or silent, the number of people carrying the virus is much higher than the reported case count. During and just after the monsoon, a fever with body ache deserves more attention than it would in a cooler month.

• Use a mosquito repellent that contains DEET, picaridin or IR3535, reapplied as the label directs.
• Wear clothes that cover your arms and legs, particularly in the early morning and early evening.
• Use window screens, and sleep under a net for daytime naps as well as at night.
• Use coils or vaporisers in rooms where mosquitoes get in.
• Cover, empty and scrub water containers, coolers, flower pots, buckets and drums once a week. Aedes aegypti breeds in clean water close to homes.
• Clear stored junk, tyres and coconut shells where rainwater collects.
• If you already have dengue, stay under a mosquito net during the day for the first week of illness so that mosquitoes do not pick up the virus from you and pass it on.

No dengue vaccine is licensed or available in India at present, so there is no dengue vaccine to ask your doctor for here. Vaccines licensed in some other countries are approved only for narrow groups, and the criteria differ from country to country: one is offered only to children aged 6 to 16 years in high-transmission areas, and another only to people who have had dengue before and are travelling to a country where it is common. Travellers should get advice from a travel clinic. For most people, prevention rests on avoiding mosquito bites and reducing breeding sites around the home.