By Dr Eddy Bajrovic*
Some of the most popular overseas holiday destinations with Australian travellers have made the list of Top 10 dengue fever countries.
Compiled for the first time from maps showing global vulnerability to dengue, the 10 countries with the highest incidence include:
1. Brazil
2. Indonesia
3. Vietnam
4. Mexico
5. Venezuela
6. Thailand
7. Philippines
8. Colombia
9. Malaysia
10. Honduras
The dengue maps were developed by the United Nations University’s Institute for Water, Environment and Health in Canada to illustrate the dynamic seasonal expansion and contraction in rates at four times during the year – January, April, July, and October.
While dengue is not yet firmly entrenched in every vulnerable region, the maps show where it could become a consistent danger, including Australia’s north.
Growing worldwide travel risk
Spread by Aedes aegypti and Aedes albopictus mosquitoes, dengue is the world’s fastest growing vector-borne disease.
The virus occurs in 128 countries and around 390 million people are infected annually. Of these, an estimated 250,000–500,000 will become severely ill, while an average 20,000 will die, according to the WHO.
Dengue is now a significant risk for many Australians visiting tropical and sub-tropical destinations. Last year 1720 returned travellers and overseas visitors ‘imported’ dengue into Australia, while 1064 have fallen victim in the first half of 2015 – mainly after visiting Asian countries.
These travel-linked cases create the very real prospect that the disease could become entrenched in North Queensland and other places where the transmitting mosquitoes are found.
Rising temperatures open new frontiers
While the new dengue maps confirm the consistent exposure to dengue of countries on or near the equator, it’s also become clear that global warming will see dengue spread to new regions.
Conditions in West and Central Africa, which already bear the heaviest global burden of malaria, will become particularly favourable for dengue.
In addition, large parts of Europe and the Andes regions of the Americas – areas which today remain too cold for Aedes mosquitoes to survive winter – will also face a ‘serious threat’ from dengue in decades to come, the experts say.
Chikungunya, Zika also spreading
If the dengue juggernaut isn’t enough, Chikungunya and Zika, two other viruses spread by Aedes mosquitoes, are also causing alarm as they spread across two regions: the Caribbean and the Americas, and the Pacific.
In the Americas, more than 1.5 million cases of Chikungunya have been recorded in the last 19 months, while a handful of Pacific countries have seen tens of thousands of cases.
There were just 108 traveller-imported Chikungunya cases in Australia in 2014, but rates have been steadily increasing in recent years. Already this year there have been 73 infections.
(Media reports indicate only a few cases of Zika virus in Australia: It’s still so ‘new’ that it is not yet a notifiable disease here.)
Dodging insect diseases
It takes just one bite from an infected mosquito to get any of the mosquito-borne diseases and avoiding bites is difficult – especially in a tropical or sub-tropical country.
Because there are no vaccines or prevention medication for dengue, Chikungunya or Zika, prevention is all about knowing where the Aedes mosquitoes are found, when they are most active, and reducing the number of bites you get.
So, it’s important to:
CHOOSE A REPELLENT THAT WORKS: DEET is still the gold standard when it comes of active ingredients in repellents and the higher the concentration, the longer the protection. However, unless you’ll be spending long periods exposed to mozzies, 40% DEET formulations providing 6 hours’ protection are sufficient. Products containing 20%-30% DEET protect for over 4 hours, while 10% formulations provide at least 2 hours of protection. Picaridin is also very effective and recommended by health authorities worldwide. A 20% Picaridin-based formulation will protect for around 4 hours. Finally, some oil of eucalyptus formulations last for up to 6 hours. (Low-dose DEET- or picaridin-based repellents are suitable for children as young as 3 months.) TIP – Check with your doctor before using any repellent on your child – especially if he/she has a skin condition – and don’t allow children to apply repellent themselves.
APPLY REPELLENT TO ALL EXPOSED SKIN: Only a thin coating of repellent should be applied to exposed skin, avoiding the eyes, mouth, wounds, or rashes. TIP – It’s a good idea to wash repellent off kids when it’s no longer needed.
SEEK AND DESTROY MOZZIES: The good news is that mosquitoes don’t fly far for food; the bad news is that they can breed in a very tiny amount of water. Because human blood is their favourite, they are typically found close to where people live. TIP – On arrival, turn over or get rid of any container on the balcony or garden that could be a potential breeding site and check the screens on windows and doors.
AVOID THE ‘RUSH HOUR’: While Aedes mosquitoes bite throughout the day, dawn, dusk, and early evening are when they’re most active. If coming indoors isn’t possible, change into lightweight long pants and long-sleeved shirts, plus shoes and socks, and freshen up repellent on exposed skin. This is particularly important for kids, who are an easy target. TIP – Protect babies by covering their strollers with a lightweight gauze netting.
Finally, before you fly, check on the risk of mozzie diseases at your destination by calling Travelvax Australia’s travel health advisory service on 1300 360 164 (toll-free from landlines).
Our advisers will also tell you if malaria is a risk at your destination.
* Dr Bajrovic is the Medical Director of Travelvax Australia.