Dengue fever, Chikungunya fever, Zika fever…
Eh? Zika fever? Never heard of it!
That’s been the reaction from readers who recently saw the ‘new’ mosquito-borne disease mentioned in the list of global disease outbreaks we compile each week for travellers, the travel trade, and travel medical professionals.
Even travel doctors have been reaching for medical literature to research the little known virus.
Zika virus (ZIKV) is a flavivirus that is closely related to some more familiar mosquito-borne diseases such as dengue fever, yellow fever, West Nile, and Japanese encephalitis (JE). The virus causing Chikungunya is an alphavirus but produces a similar clinical illness.
Zika was first discovered in the Zika Forest in Uganda in 1947 but not detected in humans until 1968 in Nigeria. Since then it has appeared in isolated areas of India, Malaysia, the Philippines, Thailand, Vietnam, and Indonesia, including Lombok Island.
It made its first appearance outside Africa and Asia in 2007 when it caused a major outbreak on Yap Island and some of its neighbours in the remote Micronesia group in the Western Pacific. In recent weeks, several hundred cases have been reported more than 8500km away in the islands of French Polynesia, including Tahiti, Tahaa, Uturoa, Bora-Bora, Taiohae, Arutua, and others.
The symptoms of Zika
Fortunately, Zika generally causes milder illness in comparison with its viral ‘cousins’, the sometimes fatal yellow fever, JE, and even dengue fever (its haemorrhagic variety can cause death).
The symptoms of Zika virus include a rash, pain in the joints, and the eye condition, conjunctivitis. These usually last for between 4-7 days, but rarely result in any long-term ill-effects (although the joint pain may linger for weeks, even months).
Who is at risk?
– Travellers who go to destinations in Africa, Asia, and the Western Pacific.
– Those who live or stay for extended periods in tropical countries are at the highest risk – especially during and just after the rainy season, when transmission rates are highest.
– However, even visitors on brief stays could be infected. (Many of the Australians who have picked up dengue in recent years had been on short holidays.)
How is it spread?
Zika virus is passed on from person to person through bites from Aedes mosquitoes, most commonly Aedes aegypti, which also transmit dengue, Chikungunya, and yellow fever, and possibly Aedes albopictus, better known as the Asian Tiger. (Aedes species do not transmit JE or West Nile, which are both spread by various Culex species.)
– Have distinctive white markings or bands.
– Live in and around domestic buildings, but can be found in any urban setting, including leafy gardens and outdoor restaurants (even in 5-star hotels and resorts). Their favourite habitats are cool, shady places close to humans where small amounts of water collect to provide breeding places.
– Bite mainly during the day, but also into the evening. (Your chance of being bitten is highest a couple of hours after sunrise and just before sunset, when Aedes mosquitoes feed intensely. However, they can bite at any time.)
– Are difficult to eradicate by fogging and are quick to repopulate favourable habitats.
How to reduce mosquito bites
In the tropics, it’s difficult to avoid being bitten by insects – especially mosquitoes. But, it’s important to give it your best shot.
By taking the following precautions you will lower your chances of getting Zika, dengue, Chikungunya, or any of the diseases spread by mosquitoes and other insects.
– Check that your room is well screened, with no tears or holes in the insect mesh. (If it’s available, use the air conditioning. Mozzies don’t like cool, fast-moving air.)
– Use insect repellent on ALL exposed skin when outdoors.
– Choose a repellent that contains one of the following active ingredients: DEET, picaridin (KBR 3023), oil of Lemon Eucalyptus/PMD, or IR3535 and follow the instructions on the label on how often to apply it (remember it will wash off in water).
– Wear loose, long-sleeved shirts and long pants when outdoors – especially in the early morning and the evening around sunset.
– For higher levels of protection, travellers can soak clothing in permethrin. If you’re staying in budget accommodation that may not always be screened pack a permethrin-impregnated bed net to sleep under. (The contact insecticide repels mosquitoes and other insects, and also kills them when they land on the treated material. However, permethrin shouldn’t be applied directly on your skin.)
– If using sunscreen, apply it BEFORE insect repellent.
Read more on protecting yourself against insects.
NB – Insect-borne diseases are a common cause of post-travel illness. If you return from a trip abroad and get sick (especially with a fever), seek medical care immediately and remember to tell your travel doctor or GP about your recent overseas travel.
The rising risk of mozzie diseases
The medical director of Travelvax Australia, Dr Eddy Bajrovic said the appearance of the Zika in more areas of Asia and far-flung destinations in the Pacific is yet another reason for Australians travelling in the region to protect themselves against biting insects.
“Yellow Fever and Japanese encephalitis are the only mosquito-borne diseases for which there are effective vaccines,” Dr Bajrovic said.
“However, as there are numerous insect-borne diseases, travellers should take the full range of measures to protect themselves from bites.
The spread of ZIKV across the Pacific could be difficult to detect because it can easily be confused with dengue in earlier, serology-based diagnostic tests. For that reason, Zika might also contribute to illness during dengue outbreaks.
(A new test is now available that differentiates between Zika and dengue virus infections.)
Dr Bajrovic said that with the ready availability of rapid international flights there is a very real potential for Zika to become firmly established across Asia, in Latin America, the Caribbean and the southern states of the USA, just as dengue has.
While Zika infection is usually mild, experts warn that the same was said about West Nile virus, a ‘relative’ of Zika. West Nile virus was thought to be relatively innocuous before large outbreaks resulting in significant fatalities and severe, permanent injury began occurring in North America and Europe in recent years.
Like to know more about the health risks of your next holiday or business destination? Call Travelvax Australia’s travel health advisory service on 1300 360 164 (toll-free from landlines) for country-specific, no-obligation advice. You can also book an appointment to see a team of travel health professionals for required or recommended vaccinations and personalised travel health advice.