Thanks to Greg Folkers for sending the link to this report in PLOS Current Outbreaks: Zika Virus, Elevation, and Transmission Risk. The abstract:
Introduction: Zika virus has appeared in the Americas in the form of a major outbreak, and is now known to cause birth defects when pregnant women are infected. As a result, the Centers for Disease Control and Prevention issued travel guidelines, in the form of an elevational risk definition: destinations below 2000m are considered as at-risk.
Methods: We explored the distribution of known Zika virus vector mosquito species in relation to climatic conditions, elevation, latitude, and air traffic connections to the United States.
Results: In view of the tropical and subtropical nature of the mosquito species that are the primary Zika virus vectors, we point out that climate varies rather dramatically with respect to elevation and latitude, such that a single elevational criterion will be a poor predictor of potential for transmission.
Discussion: We suggest an initial adjustment would consider latitude in addition to elevation; a more definitive, quantitative analysis of risk would consider variables of ecology, climate, human condition, and connectivity of areas.