The Centers for Disease Control and Prevention (CDC) today
released the final 2012 national surveillance data for West
Nile virus activity. To access the information, please
A total of 5,674 cases of West Nile virus disease in people,
including 286 deaths, were reported to CDC from 48 states
(excluding Alaska and Hawaii). Of all West Nile virus
disease cases reported, 2,873 (51 percent) were classified
as neuroinvasive disease (e.g., meningitis, encephalitis, or
acute flaccid paralysis). The dates of illness onset (when
the patients’ illness began) ranged from March through
The numbers of neuroinvasive, non-neuroinvasive, and total
West Nile virus disease cases reported in 2012 are the
highest since 2003. The number of deaths is the highest
since cases of WNV disease were first detected in the United
States in 1999.
In 2012, 62 percent of all reported West Nile virus
cases—were concentrated in California, Louisiana, Michigan,
Mississippi, , Oklahoma, South Dakota, and Texas.
Texas reported 33 percent of all reported West Nile virus
cases in 2012.
Last summer’s outbreak likely resulted from many
factors, including higher-than-normal temperatures that
influenced mosquito and bird abundance, the replication of
the virus in its host mosquitoes, and interactions of birds
and mosquitoes in hard-hit areas. Because the factors that
lead to West Nile virus disease outbreaks are complex, CDC
cannot predict where and when they will occur.
Each spring, CDC releases the final West Nile virus case
surveillance data for the previous year. The data include
confirmed and probable human disease cases reported to
ArboNET by state and local health departments. ArboNET is
the national, electronic surveillance system established by
CDC to assist states in tracking illness caused by West Nile
virus and other viruses transmitted by mosquitoes or ticks.
Last year's large outbreak is a reminder that it is
important for people to protect themselves from West Nile
virus, especially as we head into summer and mosquitoes
become more active. The best way to prevent West Nile virus
disease is to avoid mosquito bites:
Use insect repellents when you go outdoors. Use
repellents containing DEET, picaridin, IR3535, and
para-menthane-diol (PMD) because these repellents provide
longer-lasting protection than other products. Always
follow the instructions on the label.
Wear long sleeves and pants at dawn and Dusk when many
mosquitoes are most active.
Repair or install screens on windows and doors. Use
air conditioning, if you have it.
Help reduce the numbers of mosquitoes around your home.
Empty standing water from items such as gutters, flowerpots,
buckets, and kiddie pools. Change birdbaths weekly.
U.S. DEPARTMENT OF HEALTH AND