Quick answer
Dengue is present in Sri Lanka all year, but cases usually rise a few weeks after heavy rain: roughly June and July after the southwest monsoon onset, and roughly November to January after the second inter-monsoon and northeast monsoon. Most cases are in towns, especially Colombo and the Western Province. The dengue mosquito bites mainly by day, around dawn and late afternoon, so daytime repellent and covering up matter. Sri Lanka has been free of local malaria since 2016.
Key takeaways
- Dengue is present all year, but cases usually rise a few weeks after heavy rain.
- The two peaks are roughly June to July and November to January.
- Most cases are in urban areas, especially Colombo and the Western Province.
- The Aedes mosquito bites mainly during the day, around dawn and late afternoon.
- Sri Lanka was certified free of malaria by the World Health Organization in 2016.
What dengue is
Dengue is a viral infection spread by Aedes mosquitoes, mainly Aedes aegypti and Aedes albopictus. It causes sudden high fever, severe headache, pain behind the eyes, joint and muscle pain and sometimes a rash. Most people recover within a week or two, but a small proportion develop severe dengue, which needs hospital care.
There is no specific treatment, so prevention matters most. Vaccines exist in some countries, but their use for travellers depends on age and previous infection, so a travel clinic is the right place to ask. Paracetamol, rather than aspirin or ibuprofen, is the usual advice for fever while dengue is possible.
This page is general information, not medical advice. Anyone with a high fever in Sri Lanka or after returning home should see a doctor and mention the trip.
When the risk rises
The Aedes mosquito breeds in small pools of clean standing water, such as blocked gutters, discarded containers, plant pots and old tyres. Heavy rain fills these sites, and a few weeks later mosquito numbers and dengue cases rise.
That gives two seasonal peaks. The first follows the southwest monsoon onset in late May, with cases usually highest in June and July, especially in the Western, Southern and Sabaragamuwa provinces. The second follows the second inter-monsoon and the northeast monsoon, with cases usually rising from November to January, including in the east and north.
The pattern varies year to year, and outbreaks can happen outside these windows. The Ministry of Health's epidemiology unit publishes weekly case counts by district.
- →First peak: roughly June to July.
- →Second peak: roughly November to January.
- →Lowest: usually the drier months of February to April.
Where it is most common
Dengue is mainly an urban and suburban illness. The Colombo, Gampaha and Kalutara districts in the Western Province usually report the most cases, followed by other towns such as Kandy, Galle, Jaffna, Batticaloa and Trincomalee in their rainy seasons.
Remote parks, tea estates and high hill country areas see fewer cases, partly because there are fewer people and partly because the mosquito is less common at altitude. The risk for a visitor is concentrated in time spent in towns and in gardens around guesthouses.
- →Highest: Colombo, Gampaha, Kalutara.
- →Seasonal: Kandy, Galle, Jaffna, Batticaloa, Trincomalee.
- →Lower: high hills and remote parks.
Avoiding bites
The Aedes mosquito is a day biter, most active for a couple of hours after sunrise and before sunset, and it often bites around the ankles and indoors. That is different from the night-biting mosquitoes many travellers think of, so bed nets alone are not enough.
The most effective habits are simple: use a repellent containing DEET, picaridin or oil of lemon eucalyptus on exposed skin during the day, reapply after swimming or sweating, wear long, light clothing at dawn and dusk, and choose rooms with screens or air conditioning. Hotels in Sri Lanka usually manage standing water around their grounds.
- →Repellent during the day, not just at night.
- →Long, light clothing at dawn and late afternoon.
- →Rooms with screens or air conditioning.
Planning around dengue
There is no need to avoid Sri Lanka because of dengue. The risk to a short-stay visitor who uses repellent is low. Travellers visiting in June and July or November to January should simply take more care in towns, and anyone with a fever during or after the trip should see a doctor.
Lankan Stays & Trails chooses hotels with screened or air-conditioned rooms and well-kept grounds, and drivers know where the nearest good clinic or hospital is on every route.
Frequently asked questions
When is dengue season in Sri Lanka?
Dengue is present all year, but cases usually rise a few weeks after heavy rain: roughly June to July after the southwest monsoon onset, and roughly November to January after the second inter-monsoon and northeast monsoon. The drier months of February to April usually have the fewest cases.
Is dengue a risk for tourists in Sri Lanka?
The risk is real but low for short-stay visitors who use repellent during the day and cover up at dawn and dusk. Most cases are in towns, especially in the Western Province. Anyone with a high fever during or after a trip should see a doctor.
Which mosquito spreads dengue and when does it bite?
Dengue is spread by Aedes mosquitoes, mainly Aedes aegypti and Aedes albopictus. They bite mainly by day, especially for a couple of hours after sunrise and before sunset, often around the ankles and indoors. Daytime repellent matters more than bed nets.
Is there malaria in Sri Lanka?
No. Sri Lanka was certified free of malaria by the World Health Organization in 2016, and there has been no local transmission since. Antimalarial medication is not usually needed. Dengue and other mosquito-borne illnesses are still present, so bite prevention remains important.
Where in Sri Lanka is dengue most common?
Dengue is most common in towns, especially the Colombo, Gampaha and Kalutara districts in the Western Province. Other towns such as Kandy, Galle, Jaffna and Batticaloa see seasonal rises. High hill country and remote parks have fewer cases.
What repellent works against dengue mosquitoes?
Repellents containing DEET, picaridin or oil of lemon eucalyptus work against Aedes mosquitoes. Apply them to exposed skin during the day, not just in the evening, and reapply after swimming or heavy sweating. Light, long clothing adds protection at dawn and dusk.
How does Lankan Stays & Trails reduce dengue risk for guests?
Hotels are chosen with screened or air-conditioned rooms and well-kept grounds, and guests are reminded to use daytime repellent in the rainy months. Drivers know the nearest good clinic or hospital on every route, in case anyone develops a fever.