Texas Lifestyle Limits Transmission of Dengue Virus

Paul Reiter, Sarah Lathrop, Michel Bunning, Brad Biggerstaff, Daniel Singer, Tejpratap Tiwari, Laura Baber, Manuel Amador, Jaime Thirion, Jack Hayes, Calixto Seca, Jorge Mendez, Bernardo Ramirez, Jerome Robinson, Julie Rawlings, Vance Vorndam, Stephen Waterman, Duane Gubler, Gary Clark, Edward Hayes

Disclosures

Emerging Infectious Diseases. 2003;9(1) 

In This Article

Abstract and Introduction

Urban dengue is common in most countries of the Americas, but has been rare in the United States for more than half a century. In 1999 we investigated an outbreak of the disease that affected Nuevo Laredo, Tamaulipas, Mexico, and Laredo, Texas, United States, contiguous cities that straddle the international border. The incidence of recent cases, indicated by immunoglobulin M antibody serosurvey, was higher in Nuevo Laredo, although the vector, Aedes aegypti, was more abundant in Laredo. Environmental factors that affect contact with mosquitoes, such as air-conditioning and human behavior, appear to account for this paradox. We conclude that the low prevalence of dengue in the United States is primarily due to economic, rather than climatic, factors.

Outbreaks of mosquito-borne infection are commonly assumed to occur wherever competent vectors and a suitable climate exist, and that "global warming" -- climate change caused by human activities -- will cause these diseases to move to higher altitudes and latitudes. In many parts of the world, however, such diseases have become uncommon, despite an abundance of vectors and an ideal climate.

Denguelike illness was first noted in the New World as a major outbreak in Philadelphia in 1780[1], and similar episodes occurred in the United States for more than 150 years. In 1922, the disease struck many major cities in the southern states, including an estimated 500,000 cases in Texas. Another widespread outbreak occurred in 1947-48[2]. In the past 50 years, however, autochthonous cases have been rare, despite an abundance of Aedes aegypti in the southeastern United States, and the arrival of millions of travelers from neighboring countries where the disease is endemic. From 1980 to 1999, only 64 locally acquired cases were confirmed in Texas, whereas 62,514 suspected cases were recorded in three adjoining Mexican states -- Coahuila, Nuevo León, and Tamaulipas. In the same period, immigration authorities reported ≤ 70 million personal crossings from these states into Texas in a single year[3]. Thus, the international border separates a dengue-endemic region from one in which the disease is rare.

Laredo, Texas, United States (population 200,000), and Nuevo Laredo, Taumalipas, Mexico (population 289,000), are essentially a single city (locally known as "los dos Laredos") divided by a small river, the Rio Grande (Figure 1). The rapid growth of this metropolitan area -- 70% in the past decade -- is mainly due to massive cross-border traffic across three multilane bridges (Laredo Chamber of Commerce. Laredo, Texas; available from: URL: http://www.laredochamber.com/contact-information.htm). In the summer of 1999, toward the end of a local dengue outbreak, we conducted a seroepidemiologic survey to examine factors affecting dengue transmission on both sides of the border.

Laredo, Texas (east of the Rio Grande river) and Nuevo Laredo, Taumalipas (west of the river). Blue, water; green, vegetation; blue-violet, roads and buildings; paler blue-violet areas, low-income neighborhoods; pink, land with little or no vegetation. (National Aeronautics and Space Administration (NASA)/U.S. Geological Survey LANDSAT 7 image [TM bands 7, 4, and 3]; courtesy of NASA.)

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