Madam, – The article by Dr Muiris Houston on globalisation helping the spread of exotic diseases (HEALTHplus, May 4th) raised an important issue with respect to the possible emergence of vector-borne diseases within the European Union.
However, the reason the Chikungunya virus (CHIKV) outbreak occurred in the Emilia Romagna region of Italy in September 2007 was not because mosquitoes “had adapted to a climate more temperate than their usual habitat” as the author suggests.
In the Italian scenario, a combination of several factors was responsible for this first European CHIKV outbreak. During an earlier outbreak in La Reunion spanning 2005-2006 the circulating strain of CHIKV underwent a mutation in its (RNA) genome resulting in a change in one its virus envelope proteins. It is this genetic change that allowed the virus to be transmitted by a species of mosquito that CHIKV is not naturally spread by, called Aedes albopictus, a mosquito species that relatively recently has thrived in parts of Italy.
The genetic mutation in the virus genome that allowed the transmission of CHIKV to expand its host range from Aedes aegypti (largely absent in Europe since the mid-20th century) to Aedes albopictus, combined with the presence of the latter in the local ecosystem in the Emilia Romagna region allowed this virus to be spread to 254 local inhabitants.
The fact that the patient returned from a zone that was having a largescale CHIKV endemic was also a major contributing factor. The number of people that could have been infected would have been considerably more if the local authorities had not sprayed insecticide in the immediate and surrounding areas within a few days of the first infection, and warned people to stay indoors at dusk.
It is all these factors, combined with increased global travel that give cause for concern regarding future outbreaks within Europe of other viruses, including Dengue and Yellow fever viruses. However, several preventive measures can be taken to reduce the risks of becoming infected.
In the lead-up to the holiday season, when families may be travelling to exotic destinations, several common-sense preventive measures should be taken to avoid becoming infected with a vector-borne disease such as Chikungunya. Chances of getting bitten by an infected mosquito are dramatically reduced by: removing any pools of stagnant water (buckets, pots, etc) around lodging areas where mosquitoes can breed; not being outside at dusk in an endemic region; wearing long sleeves if out; and using an appropriate mosquito repellent containing Deet. Having a mosquito net over beds and mosquito screens on doors and windows are also desirable where possible.
These are important and simple measures that Irish travellers should be aware of in advance of planning their holiday, especially if planning on an early spring 2011 trip to La Reunion, Mauritius, southern India, Indonesia, Sri Lanka or Madagascar, which are now considered Chikungunya endemic holiday destinations. – Yours, etc,