Alarm is growing in Indonesia that a new, more virulent strain of the potentially deadly Dengue Fever Virus may have emerged. There have been as many as 169 deaths from the mosquito-borne disease just this year.

In Indonesia, doctors say the Dengue fever is spreading faster and killing more victims than in past years. And medical officials in the city of Surabaya say they have detected a new sub-variant of the virus.

Like Malaria, Dengue is spread through the bites of mosquitoes. The illness, which is also known as "break-bone fever," produces symptoms of severe aches in the joints, a rash, raised temperature and nausea. There is no vaccine or cure apart from bed rest and typically about one in 20 victims - mostly children - dies of the disease.

Disease specialists say that Dengue has a four to five year cycle and that they were expecting a larger outbreak than normal this year. But they are waiting for the results of more tests to determine whether the Indonesian outbreak has been caused by a mutant strain.

Dr. Georg Petersen is the head of the United Nations World Health Organization Jakarta office and he says it is too early to sound the alarm. "There are too many other factors that explain the mortality we have seen so far to claim there is a new virus that is causing this," he says.

Dengue is common in tropical areas and is endemic across much of Asia, Africa and the Caribbean. Anywhere between 50 and a 100 million people are infected each year worldwide.

Indonesian authorities have embarked on a major mosquito eradication program in the areas where the disease has hit, and is appealing to people to make sure that there is no standing water to provide mosquitoes a breeding ground.

Health teams more accustomed to providing family planning advice are being deployed out to villages to educate people in spotting the symptoms of the disease so it can be treated early.

If the new sub-variant of the Dengue virus is confirmed, it will be just the latest in a series of health problems for Southeast Asia in general and Indonesia in particular. Less than a year ago the region was hit by Severe Acute Respiratory Syndrome - SARS - a pneumonia-like disease that killed more than 800 people. Right now, the region has been hit hard by bird flu - which has been transmitted to humans - killing nearly two dozen.