In 2012, the country experienced increased West Nile activity compared to recent years, and Louisiana was no exception, recording the highest number of cases in a decade.

The Louisiana Department of Health today issued the 2012 year-end totals for human West Nile cases detected in the State, reporting 397 total infections, of which 160 were the most serious form of the virus, neuroinvasive disease. West Nile also caused 21 deaths last year, all of which occurred within two weeks of disease onset.

Humans contract West Nile when they are bitten by mosquitoes infected with the virus. When people are infected with West Nile, the virus will affect them one of three ways. West Nile neuroinvasive disease is the most serious type, infecting the brain and spinal cord. Neuroinvasive disease can lead to death, paralysis and brain damage. The milder viral infection is West Nile fever, in which people experience flu-like symptoms. The majority of people who contract West Nile will be asymptomatic, which means they show no symptoms. These cases are typically detected through blood donations or in the course of other routine medical tests. Of the 397 West Nile cases reported in 2012, 160 were neuroinvasive disease.

"The best way to gauge how intense a West Nile season is in any given year is to compare the numbers of neuroinvasive disease cases," said LDH State Epidemiologist Dr. Raoult Ratard. "There is often more ambiguity in the milder forms of the disease and how these cases are tracked and reported because people with those symptoms might not seek medical attention, or their illnesses could be classified as something other than West Nile. People who experience the severe symptoms of neuroinvasive disease will almost always need medical attention and be confirmed as a West Nile case, so this is the most accurate benchmark for how widespread West Nile virus is among the population in a given season."

West Nile virus has been present in Louisiana since 2002, when the state experienced 204 West Nile neuroinvasive disease cases and 24 deaths. For 10 years, state health officials have conducted robust surveillance year-round, which includes working with doctors, hospitals and health care providers around the state to track human cases and reminding people to be vigilant in avoiding mosquito bites.

Nationwide, West Nile cases of all forms of the illness in 2012 were the highest they have been since 2003, and Louisiana was among the states with the highest overall case counts.

DHH's weekly Arbovirus Surveillance Reports on West Nile activity in the state, along with the 2012 year-end totals report, are available here.

For more information on West Nile activity in Louisiana and prevention tips, visit