Chikungunya epidemic on Reunion Island
After the first outbreak between March and June 2005, the chikungunya epidemic struck Reunion Island again in October 2005, before peaking in February 2006. Over the whole of this period, the French Institute for Public Health Surveillance (InVS) estimated that a total of 266,000 people presented a clinical form of the disease at some point in time. On top of the unprecedented scope of this epidemic, severe clinical forms (meningoencephalitis, encephalopathy and fulminant hepatitis) were described for this disease for the first time. Until then, it was only known for causing a syndrome similar to dengue fever of generally benign evolution, presenting as a fever, a skin rash or persistent arthralgia. 246 people were hospitalised in intensive care and some forty cases of materno-neonatal transmissions with biological confirmation were found; 254 death certificates mentioning chikungunya were listed on Reunion Island through 2006.
The explosive nature of the epidemic on Reunion Island from the start of the 2005-2006 rainy season and the associated morbidity and mortality rates have plunged the département into a health crisis with severe socio-economic consequences. 
Work conducted by the Agency
In this context, the French Ministry of Health and Solidarities and the French Overseas Ministry wanted a support mission to be created with the following objectives: 
Identify the reasons, including possible shortcomings in prevention, which allowed the epidemic to spread; Establish epidemiological forecasts and assess the risks of an epidemic and possibilities for eradication; Determine the means and assess the appropriateness of vector control methods set up, including in terms of communication, as well as the contribution of local authorities and recommend improvements; Assist the various local players where needed in their preparation to transfer vector control activities to the county council under the best conditions.
This joint IGAS/Afsset/IRD/InVS mission concluded that, without a vaccine or etiological treatment, the main means of controlling the chikungunya epidemic on Reunion Island is vector control, the measures of which aim to reduce the density of the Aedes albopictus vector; these mosquito control operations must also be accompanied by personal protection measures to protect the general population from mosquito bites.
Mosquito larvae control was conducted: initially using temephos-based biocidal products, then with Bti-based products.
Adult mosquito control was conducted: initially using fenitrothion-based biocidal products, then very rapidly with deltamethrine-based products. 
As part of a global strategy to assess the epidemic control methods, Afsset received solicited requests on several occasions: Solicited request of 26 January 2006, on the assessment of dangers and risks of temephos for humans and the environment with regard to an essential use application submitted to the European Commission; Solicited request of 10 February 2006, on the comparative assessment of adulticide vector control products and complementary application of 24 August 2006 to assess the potential substrates; Solicited request of 22 August 2006, on the assessment of risks associated with the use of insecticide products for impregnating mosquito nets and clothing; Solicited request of 24 August 2006 on the comparative assessment of larvicide products used for vector control.
Current situation of vector diseases
The InVS announced that chikungunya on Reunion Island and in Mayotte had entered the inter-epidemic phase in April 2007. Circulation of the virus had diminished significantly from July 2006. Today it is only very sporadic on the islands of the Indian Ocean. Moreover, with the onset of winter in the south, the density of mosquitoes carrying the disease reduced further.
The risk on these islands of the Indian Ocean therefore seems to have passed, at least for now. In May 2007, the French Ministry of Health and Solidarities announced that “an epidemic resurgence of chikungunya is no longer imminent” on Reunion Island and in Mayotte. However, the ministries concerned added that “these regions, situated in the tropics, are still exposed to the risk of diseases spread by mosquitoes. Malaria is particularly present in Mayotte and French Guiana and dengue fever in the French départements of America”. Accordingly, the InVS states that 792 and 756 malaria cases were notified in Mayotte in 2003 and 2004 respectively, which represents an annual incidence of around 5%.
It should also be recalled that a considerable proportion of the population is not immunised (almost two thirds according to the work conducted by InVS) which means that a resurgence of the chikungunya virus is still possible on these islands. The assessment of the effectiveness and associated risks of vector control operations, as well as that of personal protection devices, is still as relevant as ever. 
Find out more about: Larvicide substitutes 
Temephos (larvicide) Adulticide substitutes Fenitrothion/deltamethrine (adulticide) Mosquito nets and impregnated fabrics
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