The Bali Times newspaper reported on June 23rd, local health authorities are calling this the worst dengue season in years. 3 Indonesian children died in Denpasar in June. The Western Australian health department has issued a warning because of the high number of Australians returning home with Dengue fever, 151 so far this year compared to just 16 for all of 2006! (Perth Now report; http://bit.ly/a2sR7J).
Dengue peaks in the rainy season (lots of water on the ground), but we're into the dry season now which means fewer mosquitoes... but they'll still be around.
Dengue seems to be bad everywhere this year. Authorities in Phuket, Thailand, report 400 cases so far this year compared to 160 for the whole of 2009. On a regional basis, Indonesia has more cases of Dengue fever than any other SE Asian country.
World health specialists say Dengue Fever is an "emerging disease". From being virtually unknown in the 1950's it is now widespread and infects more people than Malaria.
There's no cure (although most people make a full recovery) and no vaccine BUT you can take precautions to minimise your risk.
World Nomads (I work there) has a great piece on Dengue and how to avoid it here; http://journals.worldnomads.com/safetyhub/post/52684.aspx
The quick tips; wear long sleeves and trousers, preferably white and loose fitting. Cover exposed skin with repellent, and use mosquito coils in rooms.
The mosquito responsible for spreading dengue is active during the day (unlike the Malaria mosquito which is a dawn and dusk creature)and lurks in shaded, indoor areas.
Dengue fever isn't spread from human to human. it's infected human-to mosquito- to human, so stay away from places where an outbreak is known.
How bad is Dengue fever in Bali? It's worse than it's been in years, but if you're careful you can reduce your risk of getting it. No authority, Indonesian or Australian, is advising people to put off travel to Bali. Just use common sense and take precautions.
Don't forget to get travel insurance to cover medical expenses. This traveller is certainly glad they did http://journals.worldnomads.com/true-claims-stories/post/18705.aspx about 10 years ago