Synopsis
Distinguish the major Aedes-borne viral syndromes, detect dengue capillary leak before shock, investigate infection by illness timing, and protect pregnancies and future pregnancies from Zika exposure.
- Dengue, chikungunya and Zika are transmitted by day-biting Aedes mosquitoes and overlap geographically and clinically.
- Dengue commonly causes abrupt high fever, severe headache, retro-orbital pain, myalgia, nausea and rash; warning signs cluster near defervescence when capillary permeability rises.
- Chikungunya is distinguished by abrupt fever with prominent, often symmetric and disabling polyarthralgia; joint symptoms can persist for months or years.
- Zika is often asymptomatic or mild with pruritic rash, non-purulent conjunctivitis and arthralgia, but infection in pregnancy can cause congenital Zika syndrome and pregnancy loss.
- First-line acute assessment includes malaria films, FBC and haematocrit, renal and liver profiles, observations, hydration and a dated travel and symptom history.
- Confirm acute infection with pathogen-specific PCR or dengue NS1 during the early viraemic window; serology is later and flavivirus cross-reactivity can make interpretation difficult.
- Give paracetamol for fever or pain and avoid aspirin, ibuprofen and other NSAIDs until dengue has been excluded and bleeding risk has resolved.
- Dengue shock needs small, carefully reassessed isotonic crystalloid steps rather than unmonitored large-volume resuscitation because leaked fluid can produce pulmonary oedema.
- After a woman travels alone to a Zika-risk area, avoid conception for two months; if a male partner travelled alone or the couple travelled, use the current three-month precaution.
- Mosquito bite avoidance during illness reduces onward transmission where competent vectors occur; UK laboratories report confirmed dengue, chikungunya and Zika organisms under current notification rules.
Key red flags
Deterioration as fever settles, usually during illness days three to seven, is characteristic of the dengue critical phase and must not be mistaken for recovery.
Narrow pulse pressure, delayed capillary refill, cool extremities, tachycardia, oliguria or altered mental state can precede overt hypotension in dengue shock.
A rising haematocrit with rapidly falling platelets suggests plasma leakage; a falling haematocrit in an unstable patient may instead indicate bleeding.
Pregnancy with possible Zika exposure or infection needs prompt fetal-medicine and virology advice because maternal illness may be mild while fetal consequences are substantial.
Encephalopathy, myocarditis, hepatitis, renal injury, major haemorrhage or respiratory compromise warrants monitored specialist care regardless of the presumed arbovirus.
Fever after tropical travel still requires urgent malaria testing; an Aedes exposure history or rash does not safely exclude malaria.
Severe abdominal pain, repeated vomiting, mucosal bleeding, lethargy, restlessness, liver enlargement or fluid accumulation emerging near defervescence predicts deterioration.
Tachycardia, cool peripheries, delayed refill and narrowing pulse pressure may appear while systolic pressure remains normal; waiting for hypotension is unsafe.
Investigation priorities
Identify malaria, physiological instability and common organ complications before arbovirus confirmation.
Management branches
A traveller returns from an Aedes-risk area with fever, rash, arthralgia or conjunctivitis.
- Record destinations, dates, outbreak exposure, mosquito bites, day of illness, pregnancy possibility, sexual partner travel and previous flavivirus infection or vaccination.
- Use ABCDE, obtain urgent malaria testing and baseline haematocrit, platelets, renal and liver profiles; screen separately for high-consequence infection when epidemiology requires it.
- Select early PCR or antigen and later serology according to symptom onset, discussing pregnancy and uncertain results with virology or RIPL.
- Give explicit return instructions for defervescence, abdominal pain, vomiting, bleeding, reduced urine, breathlessness, faintness, weakness or confusion.