The sun
Australia's biggest health problem for fair-skinned visitors is also one of its chief attractions: sunshine . A sunny day in London, Toronto, or even Miami, is not the same as a cloudless day in Cairns, and the intensity of the Australian sun's damaging ultraviolet rays is far greater. Whether this is because of Australia's proximity to the reputed ozone hole is a matter of debate, but there's absolutely no doubt that the southern sun burns more fiercely than anything in the northern hemisphere, and you need to take extra care.

Australians of European origin, especially those of Anglo-Saxon or Celtic decent, could not be less suited to Australia's outdoor lifestyle, which is why two out of three Australians are statistically likely to develop skin cancer in their lifetime, the world's worst record. About five percent of these will develop potentially fatal melanomas , and about a thousand die each year. Looking at the ravaged complexions of some older Australians (who had prolonged exposure to the sun in the days before there was an awareness of the great dangers of skin cancer) should be enough to make you want to cover yourself with lashings of the highest factor (SPF 35+) sun block, widely used and sold just about everywhere. Sunscreen should not be used on babies less than six months old: instead, keep them out of direct sunlight. What looks like war paint on the noses of surfers and small children is actually zinc cream ; the thick, sticky waterproof cream, which comes in fun colours, provides a total blockout and is particularly useful when applied to protruding parts of the body, such as noses and shoulders.

These days, Australians are fully aware of the sun's dangers, and you're constantly reminded to " Slip, Slop, Slap ", the government-approved catch phrase reminding you to slip on a T-shirt, slop on some sun block and slap on a hat - sound advice. Pay attention to any moles on your body: if you notice any changes, either during or after your trip, see a doctor; cancerous melanomas are generally easily removed if caught early. To prevent headaches and - in the long term - cataracts, it's a good idea to wear sunglasses ; look for "UV block" ratings when you buy a pair.

The sun can also cause heat exhaustion and sunstroke , so as well as keeping well covered up, stay in the shade if you can. Drink plenty of liquids: on hot days when walking, experts advise drinking a litre of water an hour - which is a lot to carry. Alcohol and sun don't mix well; when you're feeling particularly hot and thirsty, remember that a cold beer will actually dehydrate you.

Wildlife dangers
Although mosquitoes are found across the whole of the country, malaria is not endemic; however, in the tropical north there are regular outbreaks of similarly transmitted Ross River Fever and Dengue Fever, chronically debilitating viruses which are potentially fatal to children and the elderly. Medical researchers believe that mosquitoes as far south as Sydney may be carrying the Ross River virus, which is reason enough not to be too blasé about mozzie bites. Aeroguard and Rid are the popular brands of insect repellent.

The danger from other wildlife is much overrated: snake and spider bites, and crocodile and shark attacks are widely publicized and an essential part of the perilous Outback myth - nonetheless, all are extremely rare. There are always scares, such as when a couple of people died from being bitten by flying foxes infected with the rabies-like lyssa virus in Queensland in 1996 - it's best not to handle bats, should you have the opportunity. Rabies itself is unknown in Australia.

The way to minimize danger from saltwater crocodiles (which actually range far inland) is to keep your distance. If you're camping in the bush within 100km of the northern coast between Broome (WA) and Rockhampton (QLD), make sure your tent is at least 50m from waterholes or creeks, don't collect water at the same spot every day or leave any rubbish around, and always seek local advice. Four-wheel drivers should take extra care when walking creeks prior to driving across.

Snakes almost always do their best to avoid people and you'll probably never see one. They're more likely to be active in hot weather, when you should be more careful. Treat them with respect, and it's unlikely you'll be bitten: most bites occur when people try to catch or kill snakes. Wear boots and long trousers when hiking through undergrowth, collect firewood carefully, and, in the event of a confrontation, back off. Sea snakes sometimes find divers intriguing, wrapping themselves around limbs or staring into masks, but they're seldom aggressive. If bitten by a snake, use a crepe bandage to bind the entire limb firmly and splint it, as if for a sprain; this slows the distribution of venom into the lymphatic system. Don't clean the bite area (venom around the bite can identify the species, making treatment easier), and don't slash the bite or apply a tourniquet. Treat all bites as if they were serious and always seek immediate medical attention, but remember: not all snakes are poisonous, not all poisonous snakes inject a lethal dose of venom every time they bite, and death from snakebite is rare.

Two spiders whose bites can be fatal are the Sydney funnel-web , a black, stocky creature found in the Sydney area, and the small redback , a relative of the notorious black widow of the Americas, usually found in dark, dry locations. January and February are the months in which there is the greatest danger of bites by both. Treat funnel-web bites as for snakebite, and apply ice to redback wounds to relieve pain; if bitten by either, get to a hospital - antivenins are available. Other spiders, centipedes and scorpions can deliver painful wounds but generally only cause serious problems if you have allergies.

Ticks, mites and leeches are the bane of bushwalkers, though spraying repellent over shoes and leggings will help keep these pests away in the first instance. Ticks are poisonous and you may want to check yourself over after a hike, but you'll probably feel them - look for local stinging and swelling (usually just inside hairlines) and you'll find either a tiny black dot, or a pea-sized animal attached, depending on which species has bitten you. Kill the tick with kerosene and then, using tweezers, pull it off, while trying to avoid squeezing the animal's body, which will inject more venom. Some mites cause an infuriating rash known as "scrub itch", which characteristically appears wherever your clothes are tightest, such as around the hips and ankles. Unfortunately, there's not much you can do except dab on more kerosene to kill the mites, take antihistamines and wait a day or two for the itching to stop. Leeches are gruesome but harmless; insect repellent, fire or salt gets them off the skin, though bites will bleed heavily for some time.

More serious is the threat from various types of jellyfish (also known as stingers or sea wasps), which occur in coastal tropical waters through the summer months. Two to watch out for are the tiny irukanji and saucer-sized box jellyfish, though both are virtually invisible in water. Irukanji have painless stings, but their venom causes cramping and severe abdominal pain, and side-affects which can continue for months. Box jellyfish stings leave permanent red weals, and the venom can cause rapid unconsciousness and even kill if the weals cover more than half a limb. Treat stinger victims by dousing the sting area (front and back) with liberal amounts of vinegar (never rub with sand or towels, or attempt to remove tentacles from the skin - both could trigger the release of more venom); apply mouth-to-mouth resuscitation if needed, and get the victim to hospital for treatment. Whatever the locals are doing, don't risk swimming on tropical beaches during the stinger season (roughly Oct to May).

Various health hazards
Australia has one of the lowest rates of AIDS infection in the world, largely because the population caught on very early to the need for safe sex, which has been promoted heavily. Infected needles are also a danger, not only among intravenous drug users but also from ear-piercing and tattooing. The Australian National Council on AIDS (ANCA) has centres all over the country, and you'll find AIDS helplines listed in the major cities in this section of the website.

Other health hazards are far less pressing. Tap water is safe to drink everywhere. It doesn't always taste good, but bottled water is commonly available. One thing to watch out for in the hot and humid north is tropical ear , a very painful fungal infection of the ear canal. Treatment is with ear drops and if you think you might be susceptible, use them anyway after getting wet.

Although you're unlikely to find yourself in the path of a raging bushfire , it helps to know how to survive one. If you're in a car, don't attempt to drive through smoke but park at the side of the road in the clearest spot, put on your headlights, wind up the windows and close the air vents. Although it seems to go against common sense - and your natural instincts - it's safer to stay inside the car . Lie on the floor and cover all exposed skin with a blanket or any covering at hand. The car won't explode or catch on fire, and a fast-moving wildfire will pass quickly overhead. If you smell or see smoke and fire while walking , find a cleared rocky outcrop or an open space: if the terrain and time permits, dig a shallow trench - but in any event, lie face down and cover all exposed skin.

AIDS organizations ACON (AIDS Council of NSW), PO Box 350, Darlinghurst, NSW 2010 (tel 02/9206 2000 or free call 1800 063 060, www.acon.org.au ); AIDS Trust of Australia, PO Box 1030, Darlinghurst, NSW 2010 (tel 02/9310 1066).