![[ Visit Client Website ]](images/banner.jpg)
BACKGROUND: In 2012, the US experienced the largest West Nile Disease (WND) outbreak in history. Texas accounted for 32.9% of all cases and 31.1% of all deaths in the US, respectively. City of Houston (COH) also experienced the largest outbreak (n=75) ever with four deaths since the first documented case reported in 2002. While nationally WNV was relatively calm for the last two years, COH again experienced an even larger outbreak with 86 cases but no death in 2014. This abstract aims to describe the WND epidemiological trend in Houston.
METHODS: WND case definition is based on Epi Case Criteria Guide from Texas Department of State Health Services (DSHS). WND human specimens (serum and/or CSF) are first tested at COH and DSHS laboratories, then forwarded to CDC for Plaque Reduction Neutralization Tests. Final Investigation statuses are based on both clinical presentations and laboratory results. The mosquito samples are collected and tested by the Harris County Public Health and Environmental Services Mosquito Control Division (HCPHES-MCD). Information of human cases, positive mosquito samples are analyzed and shared between the two entities to enhance ground and aerial spray actions for geographically targeted mosquito control activities.
RESULTS: Between 2008 and 2011, an average of 6 WND cases was reported to COH annually (range from two to 13). In 2012, COH investigated 75 cases including four fatalities. Thirty-eight cases (50.7%) were classified as West Nile Neuroinvasive (WNNI) and 37 cases (49.3%) were classified as West Nile Fever (WNF). There was an over twelve-fold-increase in 2012 as compared to the preceding four year averages. While no case was detected in 2013, the outbreak in 2014 netted a total of 86 cases with the highest ever of WNNI to WNF ratio of almost five to one. In the same year the HCPHES-MCD also recorded an unprecedented positive WNV samples (n=1,286), accounting for over 60% of total positive samples in the State (n=2,029).
CONCLUSIONS: WNV is a multi-factorial mosquito-borne zoonotic arboviral disease that involves environment, weather, vectors, and host. The almost back to back WND outbreaks in 2012 and 2014 in COH provides a window opportunity to understand the epidemiological characteristics, which may help to strategize comprehensive control plans and minimize the impact of future outbreaks.