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In turn, trop­i­cal des­ti­na­tions can be hot spots of mos­qui­to-borne dis­eases such as dengue. In fact, Aus­tralian health author­i­ties have warned trav­ellers to Bali to be aware of the risk of dengue, with cas­es surg­ing in the region.

So here’s how to pro­tect your­self and your fam­i­ly on holidays.

What is dengue?

Dengue virus infec­tion (com­mon­ly known as dengue fever, or just dengue) is caused by virus­es spread by the bite of a mos­qui­to. The mos­qui­to species that typ­i­cal­ly trans­mit dengue are Aedes aegyp­ti and Aedes albopic­tus.

There are four strains of dengue virus. Each has the poten­tial to cause ill­ness that can range from mild to severe and poten­tial­ly life threat­en­ing.

Symp­toms typ­i­cal­ly include rash, fever, chills, headache, mus­cle and joint pain, and fatigue. Peo­ple also often report abdom­i­nal pain, nau­sea and vomiting.

While infec­tion with just one of these virus­es can make you sick, sub­se­quent expo­sure to oth­er strains can have more seri­ous health impli­ca­tions. In these cas­es, symp­toms can also include the pres­ence of blood in vom­it, bleed­ing gums and breath­ing difficulties.

Dengue infec­tion must be con­firmed via a blood test, but there are no spe­cif­ic treat­ments. Most peo­ple will recov­er on their own how­ev­er stay­ing hydrat­ed is cru­cial and pain relief can help with symp­toms. If more severe ill­ness occurs, seek urgent med­ical care.

Are travellers at risk?

The dis­ease is now endem­ic in around 100 coun­tries and an esti­mat­ed 4 bil­lion peo­ple are con­sid­ered at risk. Asian coun­tries rep­re­sent around 70% of the glob­al dis­ease bur­den. Even Europe is at risk.

One of the worst years on record was 2023, but the bur­den of dengue con­tin­ues to grow. In the first four months of 2024, Indone­sia report­ed three times as many cas­es of dengue com­pared to the same peri­od in 2023.

Dengue is not a new risk to Aus­tralian trav­ellers. Before COVID dis­rupt­ed inter­na­tion­al trav­el, the num­ber of Aus­tralians return­ing from trop­i­cal des­ti­na­tions with dengue was steadi­ly increas­ing.

For exam­ple, between 2010 and 2016, there was an aver­age annu­al increase of 22% of trav­ellers return­ing to Vic­to­ria with dengue. Almost half of these peo­ple con­tract­ed the ill­ness in Indone­sia. Bali is well doc­u­ment­ed as pos­ing a risk of dengue to travellers.

Inter­na­tion­al trav­el restric­tions due to COVID abrupt­ly stopped this trend. But now Aus­tralians are again embrac­ing inter­na­tion­al trav­el, cas­es are ris­ing once more.

Bali isn’t the only des­ti­na­tion with a surge in dengue, but we know it’s a pop­u­lar hol­i­day des­ti­na­tion for Aus­tralian trav­ellers. There’s lit­tle doubt plen­ty of fam­i­lies will be head­ing to Bali these school holidays.

How about the risk in Australia?

Not all mos­qui­toes can spread dengue virus­es. This is why the risk is dif­fer­ent in Bali and oth­er trop­i­cal regions com­pared to Australia.

Although there are more than 40 Aus­tralian mos­qui­to species known or sus­pect­ed to be trans­mit­ting local pathogens, such as Ross Riv­er virus, Aus­tralia is gen­er­al­ly free of local dengue risk due to the lim­it­ed spread of Aedes aegyp­ti and Aedes albopic­tus.

While Aedes aegyp­ti is found in parts of Queens­land, thanks to inter­ven­tions by the World Mos­qui­to Pro­gram and local author­i­ties dengue risk is low. These inter­ven­tions include the release of lab­o­ra­to­ry-bred mos­qui­toes that pre­vent mos­qui­toes in the envi­ron­ment spread­ing virus­es, as well as com­mu­ni­ty edu­ca­tion. But local cas­es occa­sion­al­ly occur.

Aedes albopic­tus is not cur­rent­ly found on the Aus­tralian main­land but is present in the islands of the Tor­res Strait. A dengue out­break has occurred there this year.

Keep mozzies away during the day, not just at night

While there is a vac­cine avail­able, it’s not rec­om­mend­ed for short-term trav­ellers. There are strict eli­gi­bil­i­ty cri­te­ria for its use, so speak to a health pro­fes­sion­al for advice.

For the major­i­ty of trav­ellers, pre­vent­ing mos­qui­to bites is the only way to pre­vent disease.

But there are dif­fer­ences in the behav­iour of dengue mos­qui­toes that mean the nor­mal mea­sures to avoid mos­qui­to bites may not be as effective.

Dur­ing the Aus­tralian sum­mer, mos­qui­toes found in local wet­lands can be incred­i­bly abun­dant. We tend to need to reach for the repel­lent and cov­er up to stop bites as soon as the sun starts going down.

Aedes aegyp­ti and Aedes albopic­tus can aggres­sive­ly bite peo­ple but they’re not as abun­dant as the swarms of sum­mer mos­qui­toes back home.

They also bite dur­ing the day, not just at night. So for those trav­el­ling to Bali or oth­er areas at risk of dengue, putting insect repel­lent on through­out the day is recommended.

What to pack for protection

If you’re stay­ing in a major resort, there’s like­ly to be a mos­qui­to con­trol pro­gram in place. This may include min­imis­ing avail­able water for mos­qui­to breed­ing in com­bi­na­tion with insec­ti­cide use. Mos­qui­toes are also less like­ly to be an issue in air-con­di­tioned accommodation.

But if you’re plan­ning to spend time out and about vis­it­ing local vil­lages, mar­kets, or in nature, it’s best to pro­tect against bites.

Light coloured and loose fit­ting cloth­ing will help stop mos­qui­to bites (and help keep you cool). Cov­ered shoes can help too – dengue mos­qui­toes love smelly feet.

Final­ly, it’s best to take some insect repel­lent with you. There may not be any avail­able at your des­ti­na­tion, and for­mu­la­tions on sale might not have been through the same thor­ough test­ing as prod­ucts approved in Aus­tralia.

Cameron Webb, med­ical ento­mol­o­gist, NSW Health Pathol­o­gy. Clin­i­cal Asso­ciate Pro­fes­sor and Prin­ci­pal Hos­pi­tal Sci­en­tist, Uni­ver­si­ty of Sydney

This arti­cle is repub­lished from The Con­ver­sa­tion under a Cre­ative Com­mons license. Read the orig­i­nal arti­cle.