Do we know what caused this felicitous outcome? Was it due to a brilliant public health intervention or effective mosquito eradication program? Was it detection and appropriate intervention with infected airline passengers? Did the virus mutate and become less virulent? Did herd immunity in the Brazilian, Caribbean, and Latin American populace interrupt the cycle of transmission from vector to victims? Was it luck?
No one (at least no one I’ve been able to find) knows for sure why this epidemic has waned so emphatically.
To me at least, that is a cause for concern. If it was just good luck or some other unknowable circumstance that caused this threat to virtually evaporate, what is to prevent bad luck or a reversal of the unknown factor to cause this virus to rear its ugly head again before long in the southern United States and other regions that harbor the mosquito known to transmit Zika? Have we dodged this bullet for good, or is there another on its way?
I believe we’ll be justified in relaxing when we can satisfy ourselves that we know what caused this illness to abate and that the current circumstances will not support its return. Until that time, relaxing does not seem wise to me.