Download Dengue along the Texas

Dengue along the Texas-Mexico Border
Mary Hayden, for NCAR Colloquium, 2006
Dengue is the most frequently reported viral disease transmitted by arthropod vectors,
primarily by Aedes aegypti mosquitoes. Dengue (DF) is endemic in most tropical and
subtropical areas; over half of the world’s population live in areas at risk for
transmission. Globally, there are an estimated 50-100 million cases of dengue infection
and 250-500 thousand cases of dengue hemorrhagic fever (DHF) per year. There are four
dengue virus serotypes, DEN-1, DEN-2, DEN-3, and DEN-4, all of which can cause
DF/DHF. After World War II, the Pan American Health Organization (PAHO) initiated
an Ae. aegypti eradication program, primarily designed to control urban yellow fever,
which reduced vector populations to below detectable levels in many Central and South
American countries, including Mexico. Due to competing health priorities, the program
was discontinued, and the species has even wider dispersal than before the eradication
campaign (PAHO, 2005). The progressive re-infestation of Latin America with Ae
aegypti that has occurred since the 1970’s has been attributed not only to decreased
funding for mosquito control, but also unplanned urbanization in tropical areas and the
rise of non-biodegradable products.
In some ways, Mexico typifies the Latin American picture in terms of dengue.
Since the late 1970s, Mexico has progressed from non-endemic to hypoendemic since the
introduction of DEN-1, to hyperendemic since the additional circulation of DEN-4 in the
early 1980s.
The 2,000 mile U.S.-Mexico border is a “unique region where the geopolitical boundary
does not inhibit social and economic interactions nor the transmission of infectious
diseases among residents on each side of the border” (Weinberg et al., 2003) Many
border cities are immediately adjacent to each other and referred to as ‘sister cities’. As a
result of this proximity, there is significant daily human traffic, nearly 3 million
pedestrian crossings and over 22 million vehicle crossings between Brownsville and
Matamoros in 2004 (US Department of Transportation 2004) across the international
border. Brownsville, Texas and Matamoros, Tamaulipas are sister cities across the Rio
Grande River (Rio Bravo) in the southernmost region of Texas known as the Lower Rio
Grande Valley (LRGV). Located in one of the poorest regions of the United States,
Brownsville, Texas has an estimated population of 161,225 and median household
income of $24,468 (about 50% of US median income) (US Census Bureau, 2005). Its
sister city, Matamoros, has an estimated population of 418,141, (Instituto Nacional de
Estadistica Geografia e Informatica, 2005) and a median household income of $10,570.
(Gibson et al., 2003). The population is growing rapidly (17% increase from 2000 to
2005), as migrants from Mexico and Central and South America move to the Mexican
side of the border to seek employment in the ‘maquiladoras’ (foreign-owned factories);
migration to the border has accelerated since the signing of the North American Free
Trade Agreement (NAFTA) in 1994.
Brownsville and Matamoros have a semi-tropical climate with an average annual
temperature of 74 degrees F and an average annual rainfall of 27.55 inches. (National
Climatic Data Center 2005). Housing in the study region is varied. In Brownsville, TX
most of the houses are one story constructed of wood, brick, or stucco. Infrastructural
services exist on the US side of the border except in unregulated colonias where there is
limited piped water, sewage or drainage. On the Mexican side of the border, conditions
can be very spare with unpaved roads, no water or waste disposal and little to no
drainage. There is a greater variety to the housing structure in Matamoros, particularly in
the invasionesr and recently urbanized settlements. Many of the houses in the invasioness
are semi-permanent and constructed of a variety of convenient materials including,
cardboard, plywood, and corrugated metal siding.
Following the re-establishment of the vector in Mexico, dengue fever has also returned.
Dengue outbreaks have occurred annually in Mexico since1978 (Koopman, et al., 1991),
and dengue hemorrhagic fever appeared in 1984 (Briseno-Garcia et al. 1996). In 1996,
there was an outbreak along the U.S./Mexican border in the Mexican state of Tamaulipas
(CDC, 1996). Outbreaks have occurred as recently as 1999 in both Texas and Mexico in
the border regions with confirmed cases of dengue on both sides of the border and
dengue hemorrhagic fever on the Mexican side (Reiter et al., 2003). The Centers for
Disease Control and Prevention (CDC), the State of Texas, and the Secretariat of Health
of Mexico have carried out enhanced surveillance through the Border Infectious Disease
Surveillance (BIDS) program since 2000.
In 2005, autochthonous transmission of DHF was documented for the first time in the
United States in Brownsville, Texas. The presence of the vector, documentation of
thousands of cases of dengue in Matamoros, Tamaulipas including almost one thousand
cases of clinical DHF suggest that dengue may already be endemic in this border region.
Furthermore, the potential exists for dengue to emerge as an important health problem in
the United States, especially in rapidly urbanizing US border populations.
The increasing case numbers of dengue and dengue hemorrhagic in Latin America
necessitate an examination of micro and macro-level changes in human and vector
ecology, factors that are critical to understanding the disease transmission dynamics.
Simultaneous circulation of multiple strains and large susceptible human populations in
rapidly growing urban areas has set the stage for the emergence of dengue and DHF as
major public health problems for Mexico and other Latin American countries and raises
concern that dengue, a disease that has not been endemic in the continental US in the last
half century, is reemerging along US-Mexico Border.
References:
Briseno-Garcia B, Gomez-Dantes H, Argott-Ramirez E, Montesano R, VazquezMartinez AL, Ibanez-Bernal S, Madrigal-Ayala G, Ruiz-Matus C, Flisser A, and TapiaConyer. (1996) Potential risk of dengue hemorrhagic fever: the isolation of serotype
dengue 3 in Mexico Emerging Infectious Diseases 2:133-5
Gibson DV, Rhi-Perez P, Cotrofeld M, De Los Reyes O, Gipson M, Rodarte RJ,
Rodriquez I, Cox A, Cunningham M, and Houston D. (2003) Cameron
County/Matamoros at the Crossroads. Cross Border Institute for Regional Development
(CBIRD-TRAC) Available:
http://www.ic2.org/publications/At%20the%20Crossroads,%202003.pdf
Instituto Nacional de Estadistica Geografia e Informatica (2005) Available:
www.inegi.gob.mx
Koopman JS, Prevots DR, Vaca Marin MA, Gomez Dantes H, Zarate Aquino ML,
Longini IM Jr, Sepúlveda Amor J. (1991) Determinants and predictors of dengue
infection in Mexico. American Journal of Epidemiology, 133(11): 1168-1178
National Climatic Data Center (2005) Available: www.ncdc.noaa.gov
Pan American Health Organization (PAHO) (2005) Number of Reported Cases of
Dengue and Dengue Hemorrhagic Fever, Region of the Americas. Available:
http://www.paho.org/common/Display.asp?Lang=E&RecID=8979
Reiter P, Lathrop S, Bunning M, Biggerstaff B, Singer D, Tiwari T, Baber L, Amador
M, Thirion J, Hayes J, Seca C, Mendez J, Ramirez B, Robinson J, Rawlings J, Vorndam
V, Waterman S, Gubler D, Clark G, and Hayes E. (2003) Texas lifestyle limits
transmission of dengue virus. Emerging Infectious Diseases 9: 86-89.
U.S. Department of Transportation (2004) Available : www.dot.gov
U.S. Census Bureau (2005) Available : www.census.gov
Weinberg M, Waterman S, Lucas CA, Falcon VC, Morales PK, Lopez LA, et al. The
U.S.-Mexico Border Infectious Disease Surveillance Profect: establishing binational
border surveillance. (2003). Emerging Infectious Diseases. (May 12, 2005). Available
from: URL: http://www.cdc.gov/ncidod/EID/vol9no1/02-0047.htm