Health ministry spokesman Jose Bustamante says four children who were bitten have died from the horrific effects of rabies infection, which is almost always fatal once symptoms develop.

Its incubation period can last several months. Vampire bats usually get their blood meals from animals, but they can sometimes attack sleeping humans when unusually hungry or infected with rabies.

This is especially a problem in areas where their rain forest habitat has been destroyed.

Replacing the cleared forest with cattle has provided a rich new living food source for the bats, which increased their population near humans.

Rabid vampire bats attacked more than 300 people in Brazil during 2004, killing 13. The following year, more than a thousand were bitten in Brazil, where 23 died.

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