Outbreak of Chikungunya Virus on the French Island Territory of Réunion

The Public Health Agency of Canada continues to monitor a significant ongoing outbreak of chikungunya virus - a mosquito-borne disease - on the French Island Territory of Réunion, located in the south western region of the Indian Ocean.

Between March 28, 2005 and February 26, 2006 a total of 2849 cases of chikungunya infection have been confirmed and notified through Réunion's surveillance network. Authorities estimate that close to 186 000 people may have become infected with the virus since March 2005.

In early 2005, a large outbreak of chikungunya occurred in the Comoros islands located off the east coast of Africa. From there, the virus circulated to other islands in the Indian Ocean and cases have been reported in Mayotte, Mauritius, Seychelles, and Réunion.

As of January 2006, transmission activity continues to occur and cases are being reported on the islands of Mayotte (2264 cases), Mauritius (2553 cases), and Seychelles (4650 cases).

French health authorities and a team from the World Health Organization (WHO) are collaborating closely with local authorities and medical practitioners to control the outbreak. Intensive measures to interrupt transmission, including increased surveillance and mosquito-control measures, continue to be implemented.

Source: Eurosurveillance, Institut de veille sanitaire (France)

Chikungunya virus is most commonly transmitted to humans through the bite of an infected mosquito, specifically mosquitoes of the Aedes genus, which usually bite during daylight hours.

Symptoms of infection, which generally last three to seven days, include the sudden onset of fever, chills, headache, nausea, vomiting, severe joint pain (arthralgias), and rash. Although rare, the infection can result in meningoencephalitis (swelling of the brain), especially in newborns and those with pre-existing medical conditions. Pregnant women can pass the virus to their fetus. Residual arthritis, with morning stiffness, swelling, and pain on movement, may persist for weeks or months after recovery. Severe cases of chikungunya can occur in the elderly, in the very young (newborns), and in those who are immunocompromised. C hikungunya outbreaks typically result in several hundreds or thousands of cases but deaths are rarely encountered.

Chikungunya v irus is most likely of African origin. Recent outbreaks have occurred in Sub-Saharan Africa, India, South-east Asia, and the Philippines.

There is no vaccine that protects against chikungunya virus. Treatment for chikungunya typically involves treating the symptoms and includes bed-rest and the use of non-aspirin analgesics during the phase of illness where the symptoms are most severe. Using protective measures to prevent being bitten by an infected mosquito remains the only means to reduce the risk of exposure.

Recommendations

The Public Health Agency of Canada reminds travellers to tropical and subtropical areas of the world that they may be at risk for contracting mosquito-borne diseases, such as malaria, dengue, Japanese encephalitis, yellow fever, and other less common diseases like chikungunya. Travellers are strongly encouraged to consult their personal physician or a travel medicine practitioner to discuss their individual risk of exposure to such diseases.

Personal Measures to Avoid Mosquitoes

The Public Health Agency of Canada strongly recommends that travellers take the following personal precautions to reduce the risk of exposure to mosquitoes:

• remain in well-screened or completely enclosed, air-conditioned areas;
• wear light-coloured clothing with full-length pant legs and sleeves; and
• use insect repellent on exposed skin.

The use of insect repellent on exposed skin is strongly recommended. Of the insect repellents registered in Canada, those containing 'N, N diethyl-m-toluamide' (DEET) are the most effective. There are specific things you should know about DEET, especially regarding its use on young children.

• Use DEET-based products as repellents on exposed skin. The higher the concentration of DEET in the repellent formulation, the longer the duration of protection. However, this relation reaches a plateau at about 30% to 35%. DEET formulations that are "extended duration" (ED), such as polymers, are generally considered to provide longer protection times, and may be associated with less DEET absorption. Formulations over 30% are not currently available in Canada, although they are available internationally, including in the United States. It should be noted, however, that products sold outside Canada have not been evaluated by Health Canada. Most repellents containing "natural" products are effective for shorter durations than DEET and for this reason are not considered the preferred products for protecting against mosquito bites.
• Regulatory agencies in western nations may differ regarding the recommended maximum concentration and application rates of DEET, especially for children. The Committee to Advise on Tropical Medicine and Travel (CATMAT) is satisfied that, for travel outside of Canada where the risk of malaria outweighs the risk of any important adverse reaction to DEET, the threshold for use of DEET should be low.
• CATMAT recommends that concentrations of DEET up to 35% can be used by any age group.
• For children, alternative personal protective measures, such as mosquito nets treated with insecticide, should be the first line of defense, especially for infants less than 6 months of age. Portable mosquito nets, including self-standing nets, placed over a car seat, a crib, playpen, or stroller help protect against mosquitoes. However, as a complement to the other methods of protection, the judicious use of DEET should be considered for children of any age. Recent medical literature from Canada suggests that DEET does not pose a significant or substantial extra risk to infants and children.
• DEET/sunscreen combination products are not generally recommended, because DEET can decrease the efficacy of sunscreens. As well, sunscreens should be used liberally and often while DEET should be used sparingly and only as often as required. If application of both is necessary, the Canadian Dermatology Association recommends that the sunscreen be applied first and allowed to penetrate the skin for 20 minutes, prior to applying DEET.

The Public Health Agency of Canada's Committee to Advise on Tropical Medicine and Travel (CATMAT) produces evidence based statements and guidelines. For additional information on Arthropod Bite Prevention visit CATMAT's Statement on Personal Protective Measures to Prevent Arthropod Bites.

As a reminder...

The Public Health Agency of Canada routinely recommends that Canadian international travellers consult their personal physician or a travel clinic four to six weeks prior to international travel, regardless of destination, for an individual risk assessment to determine their individual health risks and their need for vaccination, preventative medication, and personal protective measures.

The Public Health Agency of Canada recommends, as well, that travellers who become sick or feel unwell on their return to Canada should seek a medical assessment with their personal physician. Travellers should inform their physician, without being asked, that they have been travelling or living outside of Canada, and where they have been.

Additional information from the Public Health Agency of Canada:

• More information about arthropod bite prevention;
• More information about Canadian recommendations for the prevention and treatment of malaria among international travellers;
• More information about dengue;
• For information about yellow fever.