Dengue warning signs: when a fever needs urgent care

Dengue is common and usually mild

Dengue is a viral infection spread by day-biting mosquitoes. The World Health Organization states that about half of the world's population is now at risk, with an estimated 100 to 400 million infections each year. Most cases occur in urban and semi-urban areas of tropical and subtropical climates. Many infections cause no symptoms at all, and most of the rest are mild. That is the reassuring part. The virus can occasionally cause severe disease and death, so knowing the warning signs matters. Severe dengue is a small share of cases, but it can move quickly. The aim of this article is calm preparation, not alarm. Read it before you travel, and keep it to hand if someone in your household falls ill with a fever after time in a dengue area.

What early dengue feels like

When symptoms appear, dengue can look like flu. The NHS explains that they usually start 4 to 10 days after the bite of an infected mosquito. Common features include a high temperature, a severe headache, pain behind the eyes, muscle and joint pain, feeling or being sick, swollen glands and a blotchy rash. The Pan American Health Organization describes a sudden high fever lasting 2 to 7 days, with facial flushing and body pain. These early days are unpleasant but not usually dangerous. The critical point is not how bad the fever feels. It is what happens as the fever begins to fall. Keep noting the day the illness started, because timing guides decisions later.

The phase that matters most

Severe dengue tends to appear as the fever subsides, not at its peak. The World Health Organization notes that the symptoms of severe dengue often come after the fever has gone away. The Pan American Health Organization calls this the critical phase, beginning near the disappearance of fever, when plasma leakage, shock, severe bleeding or organ impairment can develop. Plasma leakage means fluid escaping from blood vessels into surrounding tissue, which can lower blood pressure. The NHS makes the same point: a few people develop severe dengue a few days after they first felt ill, and the temperature may start returning to normal before more serious symptoms appear. So a falling temperature is not automatically good news. Watch the person closely for the next day or two.

Warning signs that need urgent care

Both public health bodies list clear red flags. The World Health Organization names severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums or nose, fatigue, restlessness, blood in vomit or stool, being very thirsty, pale and cold skin, and feeling weak. The NHS gives a closely matching list: severe tummy pain, repeated vomiting, fast breathing, bleeding gums or nose, extreme tiredness, restlessness, and blood in vomit or stool. The Pan American Health Organization says recognition of these warning signs is essential to avoid progression to severe dengue, and that anyone with a warning sign should go immediately to the nearest health facility. Do not wait to see whether things improve overnight. Seek care the same day, and say clearly when the illness began and where you have travelled.

How to care for a mild case at home

For an uncomplicated case, the basics are rest and fluids. The World Health Organization advises rest, plenty of liquids and watching for severe symptoms. The Pan American Health Organization recommends drinking plenty of fluids, preferably oral rehydration salts, which replace water and salts lost through fever and vomiting. For pain and fever, the World Health Organization says paracetamol, also called acetaminophen, can be used. It states that non-steroidal anti-inflammatory medicines such as ibuprofen and aspirin should be avoided because they can increase the risk of bleeding. The NHS gives the same advice, noting that ibuprofen and aspirin can cause bleeding problems. Check the labels of any cold or flu remedies you take, since some contain these medicines. The Pan American Health Organization also advises against self-medicating.

How clinics sort dengue cases

Health workers use a classification to decide who needs close watching. The World Health Organization's 2009 scheme sorts patients into dengue without warning signs, dengue with warning signs and severe dengue. A systematic review in a peer-reviewed tropical medicine journal compared this with the older 1997 scheme across 12 studies, four of them prospective. For the 2009 classification, sensitivity for severe dengue ranged from 59 to 98 percent, reaching 88 and 98 percent in the prospective studies, against 24.8 to 89.9 percent for the 1997 scheme. The authors judged the 2009 classification easy to apply and advantageous for clinical use. They noted that further validation of the warning signs themselves was still needed. The review also warned that monitoring more non-severe cases is a possible cost of the newer scheme, and that the three severe dengue criteria are severe plasma leakage, severe bleeding and severe organ manifestation.

Prevention and planning ahead

Prevention rests on avoiding mosquito bites, and the dengue mosquito also bites by day, so daytime cover matters as much as evening habits. Long-lasting insecticide-treated nets offer the best protection for a sleeping person. An untreated net is only a physical barrier while it stays intact and tucked in; it fails at the first tear, gap, or limb resting against the mesh. Skin repellents such as DEET and picaridin work for a few hours and need reapplying. No method removes the risk entirely. Before travelling to a dengue area, learn the warning signs and note the nearest clinic. After returning, mention your travel history to any doctor you see for a fever. The Foundation publishes this guidance to inform, never to sell.

Sources

• Dengue and severe dengue: World Health Organization
• Dengue: National Health Service (England)
• Dengue: Pan American Health Organization
• Comparing the usefulness of the 1997 and 2009 WHO dengue case classification: a systematic literature review: The American Journal of Tropical Medicine and Hygiene, indexed by PubMed