The outbreak has killed as many as 38 Warao Indians since June 2007, 16 of those have died since June this year, including 8 children from one village.

The Warao Indians live on the Orinoco River Delta, a river wider than the Mississippi; they live a relatively primitive lifestyle in huts on stilts which have thatched roofs and travel by dugout canoe. The Warao language is of South American origin and is spoken by 20,000 people in Venezuela, Guyana and Suriname and is not known to be related to any other South American language.

According to indigenous leaders and researchers from the University of California at Berkeley, the symptoms which include fever, body pains, tingling in the feet followed by progressive paralysis are similar to rabies.

Though laboratory tests have yet to confirm the outbreak is indeed rabies, experts say it is highly likely and the disease was almost certainly carried by vampire bats whose colony had been disturbed by mining, logging or damming projects.

Anthropologist Charles Briggs and his wife public health specialist Dr. Clara Mantini-Briggs say the victims also had an extreme fear of water, suffered convulsions and grew rigid before death.

The two scientists drew attention to the unusual case and are known for their work on a cholera outbreak that killed 500 people in Venezuela in the early 1990s and have worked with the Warao for a number of years.

A research trip at the invitation of indigenous leaders to investigate the outbreak, took the two through 30 villages in the delta.

Dr. Mantini-Briggs says she was surprised to find that many Warao villages had acquired cats and they were told it was because there were too many bats that were biting the children.

Vampire bats who hunt only when it is fully dark have highly sensitive hearing which can pick up sleeping creatures. They are known to approach their victims on foot before biting them and then lapping up the blood at the site of the wound. They can survive on a purely liquid diet and their saliva contains a substance known as draculin, which prevents their prey's blood from clotting.

Venezuelan health officials apparently plan to send a medical boat to the remote water bound villages in the Orinoco River delta.

Experts say outbreaks of rabies spread by vampire bats are rare but not unknown, particularly in the tropical areas of South America.

Dr. Mantini-Briggs and her husband were themselves forced to take precautions to protect themselves after waking one morning in a Warao village to find blood on their bedding and bite marks on a finger, they will now be vaccinated.

The infectious viral disease rabies affects the nervous system of humans and other mammals and is almost always fatal.

People become infected after being bitten by an animal with rabies (a rabid animal) such as a bat, raccoon, skunk, fox, coyote, monkey,cattle, wolves and dogs and cats.