by Laurie Sullivan
Cases of Ross River fever are at a 20-year high in some of Australia’s most popular East Coast holiday destinations.
State health authorities and medical experts have urged local residents and travellers visiting destinations between NSW’s Hunter region and Queensland’s Sunshine Coast in coming weeks to protect themselves against the debilitating mosquito-borne disease.
Almost 5000 cases have already been recorded across 2 main areas this year:
South-East Queensland, including Brisbane (1900 cases) and the iconic Gold Coast (481) and Sunshine Coast (294) regions, have been hardest hit. Cairns, already battling a dengue outbreak, has recorded 193 cases, according to Queensland Health data.
NSW’s North Coast, which takes in major destinations such as Byron Bay, Ballina, Coffs Harbour, Port Macquarie and Forster, has seen the bulk of the state’s 898 cases – already well above the 12-month average of 591. Infections have also been confirmed in an around Sydney and Newcastle.
But, these lab-confirmed cases are the tip of the iceberg: Some people have no symptoms and those with mild symptoms mistake the illness for flu and don’t see their doctor to confirm its cause. NSW Health has also warned that less common – but potentially more serious – mosquito-borne diseases such as Kunjin and Murray Valley encephalitiscould also emerge.
Danger will continue into autumn
The Ross River risk looks set to continue for some weeks, one of Australia’s foremost mosquito experts, Dr Cameron Webb (pictured) warned this week.
“Although we will see fewer mosquitoes as the temperature drops, they will continue to pack a punch for some time when it comes to Ross River virus and other mosquito-borne diseases,” said Dr Webb, an entomologist based at the University of Sydney.
“Local residents, as well as travellers and holiday-makers visiting any destination in the region, shouldn’t become complacent about mozzie bites.”
He said that as the daylight hours shorten, more people are likely to be bitten at dusk if they are still outdoors and unprotected.
Summer explosion of mosquitoes
There are two main reasons for 2015’s soaring case numbers, according to Dr Webb.
“Firstly, we had one of the warmest springs on record last year,” he said.
“This created a springboard for mosquito populations to explode into summer and also contributed to the spread of Ross River virus among the wildlife, particularly kangaroos and wallabies.
“Secondly, we had a lot of rain during summer from tropical cyclones and low pressure systems – particularly in Queensland and northern NSW.
“In turn, that meant a lot of water in habitats that support both breeding mosquitoes and the infected wildlife. We’ve seen very large and diverse mosquito populations this year, ranging from the freshwater and saltwater types to those that breed in backyards.”
Threat now in south, too
Ross River virus (RRV) is one of a group of arthropod-borne viruses or ‘arboviruses’. Although animals and birds can serve as intermediary ‘hosts’, the virus is usually spread among people through the bite of a mosquito that has bitten either an infected person or animal.
RRV is most common in areas near mosquito breeding grounds, which include marshes, wetlands, waterways, and farms with irrigation systems. However, increasingly the virus is being detected in people living in or visiting areas on the fringes of regional and capital cities.
The virus is not restricted to any particular region: Even cool-climate Tasmania averages 2 dozen cases each year. It has also been reported in Indonesia, Papua New Guinea, and many Pacific islands.
In the tropics, RRV is more prevalent between January and March, when mosquito populations are high. In southern regions, the highest risk is generally in the spring-summer months, although climatic conditions can extend these seasons – as we’re seeing this year.
Risk of long-term, chronic fatigue
The incubation period for the virus is 7–9 days.
The symptoms vary widely and typically include joint pain, arthritis, fever, and a rash. A blood test is used to confirm infection, but there is no specific treatment.
Symptoms are more likely to appear in adults than children or teens, but 1-in-3 of those infected have no symptoms at all. Around 50% of sufferers report needing time off work and full recovery usually takes several weeks.
Almost all those who do experience symptoms have joint pain (95%) and fatigue (90%), while only half have a rash.
One-in-10 people with RRV continue to experience chronic fatigue 6 months after being infected, while 9% still have chronic fatigue after a year.
4 ways to dodge Ross River
A vaccine against Ross River virus is in development. Until then, avoiding the risk means avoiding bites from the various species of mosquitoes that transmit the virus.
Mosquitoes are usually most active around dawn and sunset. When outside – especially at these peak feeding times – it’s important to:
1. Cover up with light-coloured, loose-fitting clothing and covered footwear.
2. Apply an effective insect repellent (see below) – especially if you are outside around dawn or dusk.
3. Fit mosquito-proof insect screens to caravans and motor homes.
4. Create an extra insect barrier by treating tent screens, bed nets, clothing and hats with the contact insecticide, permethrin. It’s safe for both adults and kids.
Picking the right repellent
Over 60 individual repellent formulations are currently registered in Australia including aerosols, creams, lotions, pump sprays, wipes, wrist bands, and sticks.
Despite this diversity, there are only a handful of effective active ingredients, the most common being DEET (diethyltoluamide), Picaridin, and oil of eucalyptus.
The higher the concentration of the active ingredient, the longer the application lasts.
Unless you plan on spending long periods exposed to mozzies, formulations that contain 40% DEET will protect for 6 hours and are usually sufficient. Products containing 20%-30% protect for over 4 hours, while 10% formulations provide at least 2 hours’ protection.
Picaridin works just as well as DEET. It’s also odourless and a 20% formulation will protect for around 4 hours. Some oil of eucalyptus formulations last for up to 6 hours.
(Travelvax offers a range of effective repellents suitable for domestic use and travel to the tropics.)
Most natural or organic repellents are not as effective.
Cover all exposed skin
For a quick trip to the park, a low-concentration repellent will suffice.
For bush walking or a fishing trip, either apply a higher concentration repellent or remember to reapply a lower concentration repellent more frequently as needed.
Sprays are generally the most effective for arms and legs while creams and wipes are good for the face. For this reason, first apply the repellent onto your hand before rubbing it onto exposed skin.
All-over coverage is important: A vague squirt here and there is an invitation to nasty and potentially dangerous dinner guests.
Read more about Ross River virus and avoiding insect bites.