Dengue: The World's Fastest-Spreading Travel Disease

Dengue is now the mosquito-borne virus most likely to interrupt a tropical trip. It has been detected in around 129 countries, cases hit a global record in 2024, and unlike malaria — which is retreating in many places — dengue is expanding into new regions and cities. For travellers, it is a genuinely important risk across Southeast Asia, South Asia, Latin America, the Caribbean, the Pacific and increasingly parts of Africa.

The good news is that for most travellers dengue is unpleasant but self-limiting, and the protection that works is simple and the same everywhere. This guide explains how dengue spreads, why the mosquito behind it changes how you protect yourself, what makes a second infection more dangerous, and where the newer vaccine does and doesn't fit. It's based on CDC, WHO and UK NaTHNaC guidance.

How dengue spreads — and why timing matters

Dengue is caused by a virus with four related types (serotypes 1 to 4), spread by Aedes mosquitoes — chiefly Aedes aegypti. The single most useful fact for a traveller is behavioural: the Aedes mosquito bites mainly during daylight hours, with peaks around dawn and dusk, and it thrives in urban and suburban areas, breeding in tiny pools of standing water like plant saucers, tyres and gutters.

This is the opposite of the malaria mosquito, which bites at night. It's why "just use a bed net" is not enough for dengue, and why the practical rule in dengue areas is to protect yourself all day, not only in the evening.

Dengue activity rises in the rainy season in most destinations, but in many places it is a year-round risk. Our destination guides note the local picture — for example it runs year-round across Vietnam, Thailand, Bali and much of South America.

What it feels like

Many infections are mild or even symptom-free. When symptoms do appear, classic dengue brings a sudden high fever with severe headache, pain behind the eyes, marked muscle and joint aches (its old nickname, "breakbone fever," is well earned), nausea and a rash. Symptoms usually start 4 to 10 days after the bite and last about a week.

There is no specific antiviral treatment. Care is supportive: rest, fluids and paracetamol for fever and pain. One important caution — avoid aspirin and ibuprofen-type anti-inflammatories (NSAIDs) if dengue is suspected, because they increase bleeding risk. If you develop a fever in or after travel to a dengue area, this is worth telling any doctor who sees you.

Why a second infection is the dangerous one

This is the part that makes dengue different from most travel infections. Recovering from one serotype gives lifelong immunity to that type — but only partial, temporary protection against the other three. A later infection with a different serotype carries a higher risk of severe dengue, through a process where the earlier antibodies actually help the new virus. This "antibody-dependent enhancement" is also the reason the dengue vaccines are handled so cautiously (more below).

Warning signs of severe dengue typically appear as the fever starts to drop, roughly 3 to 7 days in, and are a medical emergency: severe abdominal pain, persistent vomiting, bleeding from the gums or nose, blood in vomit or stool, rapid breathing, extreme fatigue or restlessness. Anyone with these signs needs urgent hospital care. Severe dengue is rare in travellers overall but genuinely dangerous when it occurs.

Prevention is the whole strategy

Because there's no widely recommended vaccine for the average traveller, bite prevention is your dengue plan. The measures are straightforward and, helpfully, also protect against Zika, chikungunya and — at night — malaria:

• Use a repellent containing DEET or picaridin on exposed skin, and reapply as directed.
• Wear long, loose, light-coloured clothing; treat clothing with permethrin for higher-risk or rural trips.
• Be especially vigilant in daylight, particularly early morning and late afternoon, and in shaded urban spaces.
• Use air-conditioning or screened rooms where you can, and a bed net if your room isn't sealed.
• Reduce standing water around your accommodation where practical.

Because the Aedes mosquito is a daytime biter, the discipline is different from malaria — you can't simply relax during the day. Our mosquito bite prevention guide covers repellents and clothing in detail.

The vaccines — who they're actually for

Dengue vaccines exist, but for most travellers they are not part of the plan, and it's worth understanding why.

Qdenga (TAK-003) is the current vaccine, given as two doses three months apart. The World Health Organization recommends it mainly for children aged 6 to 16 living in areas with high dengue transmission — that is, for residents of endemic regions, not typical visitors.

For travellers, guidance from bodies including the UK's JCVI and several European committees is more restrictive: Qdenga may be considered for people (broadly aged 4 and older) who have had a previous, laboratory-confirmed dengue infection and are travelling to a risk area or living there long-term. It is not advised for people who have never had dengue (the "dengue-naïve," which describes most first-time and short-term travellers), because of that same enhanced-risk concern on a later infection.

The older vaccine, Dengvaxia, has effectively been withdrawn — its manufacturer discontinued production and remaining doses are only being used to complete series already started.

The practical takeaway: if you're a frequent traveller, expatriate, or someone with a confirmed past dengue infection heading somewhere with heavy transmission, ask a travel-health specialist whether Qdenga is appropriate. If you're taking a two-week trip and have never had dengue, your protection is bite prevention, not a vaccine.

The bottom line

Dengue is common, spreading, and best thought of as a day-and-night bite-prevention problem rather than a vaccine problem. Know the warning signs of severe dengue, use paracetamol rather than NSAIDs if you suspect it, and treat repellent and covered skin as non-negotiable in the tropics. The vaccine is a targeted tool for a specific group — mostly residents and previously-infected frequent travellers — not a routine traveller's shot.

See what applies at your destination on the interactive travel vaccine map, and pair this with our guides to mosquito bite prevention and when to see a travel doctor.

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This guide is general information based on CDC, WHO and NaTHNaC/TravelHealthPro guidance and is not a substitute for personalised medical advice. Vaccine recommendations vary by country and individual history — consult a travel-health professional before you travel.