Chikungunya Disease Outbreak on Reunion Island
A rapid increase in the number of chikungunya cases has been reported on the island of Reunion since late February 2025. The current outbreak started in August 2024 and more than 5,000 cases have been notified to the middle of March 2025.
CDC has issued an advisory on the current outbreak.
Chikungunya cases are increasing in other Countries
Other international destinations are also reporting outbreaks.
According to Eurosurveillance the highest number of recent cases have been reported in the Americas with more than 31,000 cases in Brazil and smaller numbers in Argentina, Bolivia and Paraguay. Chikungunya is not a benign disease. Fourteen chikungunya-related deaths have been reported in Brazil.
Eurosurveillance has provided a very useful map of destination specific case reports over a 12-month period (March 2024 to February 2025).
The disease is likely to be present in many locations where diagnostic tests are unavailable.
Understanding Chikungunya - causes and transmission
Chikungunya is a viral disease, transmitted to humans by mosquitoes. The Chikungunya virus is mostly transmitted by the bite of a female Aedes mosquito. This is the same species responsible for transmission of both dengue fever and zika.
These mosquitos mostly bite during the day but can also bite at night. Their habitat relates strongly to urbanisation with eggs being laid in small vessels containing water: bowls, buckets, dishes, and vases. Water in canoes and small ponds also provides good breeding sites. Breeding sites are found inside and outside dwellings.
Mosquito bite prevention is your best defence
The best form of prevention for Chikungunya is mosquito bite protection. This includes clothing and repellents. It is also important to be aware of the biting habits of the transmitting mosquito.
It bites mostly during daylight hours with peak activity around dawn and dusk.
Choosing the Right Repellent
DEET - Effectiveness and Precautions
The repellent of choice should contain DEET (N, N-diethyl-meta-toluamide). The higher the concentration of DEET, the longer the duration of protection. However, it should be noted that the general consensus is that there is no added benefit beyond 50% DEET concentration. DEET is toxic when ingested and may cause skin irritation in some people. If you have not used a DEET product before, or you have sensitive skin, it is advisable to test on a small area of skin before applying to larger areas of the body. DEET has been used over a long period of time, and by many millions of people with few reported serious side effects. Despite this, a few precautions should be undertaken:
- Apply DEET lightly to exposed areas only
- Where possible, wash off on returning indoors
- Do not apply to open cuts or sores
- Do not use aerosol applications to the face directly. Apply to the hands and then rub on the face avoiding the eyes and mouth
- Do not allow children <10 years to apply themselves. Weaker DEET formulations are available for children (10% DEET concentration)
- If sunscreens are to be used with repellents, then the sunscreen should be applied first. Wait 20 minutes before applying repellent
| CONCENTRATION OF DEET | APPROX. PROTECTION TIME |
|---|---|
| 30 % | 8 hours |
| 8 hours | 5 hours |
| 10 % (recommended for children) | 3 hours |
| 5 % | 2 hours |
Picaridin - a new alternative
Picaridin, also known as Icaridin (1-piperidinecarboxylic acid 2-(2-hydroxyethyl)-1-methylpropylester), is a new alternative to DEET, and is a non-toxic, non-penetrative solution that is environmentally friendly and suitable for anyone 2 years and above. The recommended level of Picaridin is 20-25% and lasts for around 4-6 hours before the need to reapply. A 20% concentration of Picaridin is thought to be as effective as 20-30% of DEET.
A new vaccine for Chikungunya approved in the United States.
A vaccine was approved by the Food and Drug Administration (FDA) in the United States in late 2023. It is manufactured by Valneva and called IXCHIQ. It is a live attenuated (weakened) vaccine providing good protection against all strains of the virus.
The vaccine is licensed for use in those over 18 years. According to CDC, it might be considered for use in travellers at high risk of exposure or those who might be at risk of serious disease.
Where is the vaccine available?
- United States: Approved
- Canada: Approved
- Europe: Approved (July 2024)
- Australia: Not available
The length of protection is currently unknown.
CDC provides a fact sheet regarding the use of the new Chikungunya vaccine.
