Multi-Dimensional Factors Associated with the 2012 West Nile Virus Epidemic in TexasWest Nile Virus is an arbovirus that is transmitted mainly by Culex mosquitos. WNV transmission is maintained through zoonotic cycles in birds which are the reservoir hosts for the disease. The majority of those infected with WNV (about 80%) will be asymptomatic and show no signs of the disease. The other 20% of the individuals infected with WNV experience symptoms of West Nile Fever. These symptoms include fever, headaches, fatigue, muscle pain, malaise, nausea and vomiting. In rare cases (about 1%), victims will experience West Nile neuroinvasive disease where the virus infects the central nervous system and results in meningitis and encephalitis. Oftentimes, this more serious type of infection will result in death. WNV has been around globally for hundreds of years, but was only recently introduced into the United States in New York in 1999. Since its introduction, the US has experienced a relatively constant number of cases over the years until 2012. In 2012, WNV have spiked dramatically. 48 of the 50 states have reported WNV infections either in humans or animals, and 5245 cases of WNV in humans has marked the highest number of WNV in the history of the U.S. (CDC, 2012). The majority of the cases this year can be attributed to 6 states with Texas being the leading contributor (about 1/3 of the total number of cases). Of the 1782 cases reported in Texas, 82 patients died. This number also represents the highest incidence of death in Texas with the next closest number of deaths being 17 in 2007 (DSHS, 2012). The spike in WNV cases has been the center of debate among health professionals, scientists, and entomologists as they strive to find possible explanations for the outbreak. Much of the increase can be attributed to the high temperatures experienced across the country as well as the rain/drought cycles that Texas has experienced.
Total (in TX)
The enzootic cycle of WNV is fueled by the presence of birds and mosquitos. Various species of birds are involved in the cycle, but the mosquitos responsible for carrying WNV usually belong to the Culex genus. In the US, Culex pipiens (Eastern US), Culex tarsalis (Midwest and West), and Culex quinquefasciatus (Southeast) are the main sources. The birds involved in the enzootic cycle are reservoir hosts that can keep the pathogen active until other mosquitos feed on the infected birds and pick of the flavivirus. These mosquitos then can infect humans with WNV resulting in cases of West Nile fever.Temperature and precipitation can greatly influence the WNV enzootic cycle. Increase in temperature increases the activity of mosquitos. As the temperature goes up, mosquitos fly around more which increases the incidence of biting and feeding. More birds are...