Zika Virus, Elevation, and Transmission Risk

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.

Keywords: Aedes; Zika; climate; disease outbreak; travel advisory.

Relationship between elevation, latitude, and minimum temperature across the Americas.

Relationship between minimum temperature of the coldest month of the year, elevation, and latitude. Black squares have a minimum temperature >20°; red squares are 15-20°; gray squares with a black outline are 10-15°, and light-gray squares are <10°.

Elevation-latitude relationships for destination airports across the Americas.

Destination airports for US travelers across the Americas (excluding the US and Canada, as Zika transmission is nil there, at least as of yet), derived from a recent risk-mapping effort focused on chikungunya virus in the Americas, and plotted in an elevation-latitude space (see Figure 1). The largest circles indicate destinations with >100,000 passengers yearly; medium-sized circles 10,000-99,999 passengers yearly, and small circles <10,000 passengers yearly; gray squares indicate availability of conditions across the Americas (same data as shown in Figure 1).

Relationships between elevation, latitude, and minimum temperature for destination airports across the Americas.

Relationship between minimum temperature of the coldest month of the year, elevation, and latitude for destination airports across the Americas. Black squares have a minimum temperature >20°; red squares are 15-20°; gray squares with a black outline are 10-15°, and light-gray squares are <10°. Note the Bogotá, Colombia, airport, with an elevation above 2000 m and subtropical conditions.