It has been confirmed that two dead monkeys did die of yellow fever. the authorities has initiated a vaccination campaign to ensure that the population is protected.

Source: ProMED 

Comment
Trinidad is not normally regarded as a yellow fever country although the virus were found in 1995. Yellow fever has a reservoir in monkeys and are transmitted to humans by mosquitoes.
In the present situation, visitors to Trinidad show have a valid vaccination against yellow fever to ensure they have the same protection as the local population.