| West Nile Virus
(WNV) Information:
- California
Surveillance and Facts
- Information prepared by California Dept.
of Health Services - Division of Communicable Disease Control:
www.dhs.ca.gov/ps/dcdc/dcdcindex.htm
The following basic
information can be found in a brochure developed by the
California Department of Health Services (DHS), and is available
at El Dorado County Environmental Management Offices.
WHAT IS WEST NILE VIRUS?
West Nile Virus (WNV) is a mosquito-borne virus that has
been found in parts of asia, eastern Europe, Africa, and
the Middle East. The virus was first detected in the United
States in 1999 in New York City.
The majority of people and animals that are
infected with the virus have a mild illness or no symptoms.
In rare cases, the virus can cause a more serious condition
called encephalitis, an inflammation of the brain. The elderly
are at a higher risk for disease caused by WNV. In 2002,
a total of 44 states reported WN virus activity and over
4,000 human cases were reported including over 250 deaths.
[Note: The first evidence
of West Nile virus (WNV) in California was in 2003. WNV
was found in mosquitoes collected in Imperial County in
August 2003 (Click
here for that DHS Press Release), and the first
human case of WNV in California was confirmed in October
2003 (Click
here for that DHS Press Release).] (Click
here for all related press releases).
HOW DO PEOPLE AND ANIMALS GET WEST
NILE VIRUS?
WNV is transmitted to people and animals by infected mosquitoes.
Only certain species of mosquitoes carry the virus and very
few mosquitoes are actually infected. A mosquito first acquires
the infection by feeding on a bird with virus in its blood.
The virus lives in the mosquito and is transmitted to a
new host in the mosquito's saliva when the insect bites
a person or animal. The virus is most prevalent from May
to October when mosquitoes are most abundant .
Human-to-human transmission of WNV generally
does not occur. However, human WNV infection was associated
with blood transfusions and organ transplants from infected
donors in 2002.
TRANSMISSION CYCLE OF WEST NILE VIRUS
2008 West Nile Virus Activity in the United
States
(Reported to
CDC as of September 3, 2008)
[from Centers of
Disease Control &Prevention (CDC)]:
WHAT ARE THE SYMPTOMS OF WEST
NILE VIRUS IN PEOPLE?
Most people who are infected with WNV
have no symptoms whatsoever. However, of those who become
ill, symptoms can include fever, headache, nausea, body
aches, mild skin rash, or swollen lymph nodes. In a few
cases, the disease will progress to encephalitis (inflammation
of the brain). The time between the mosquito bite and the
onset of illness, known as the incubation period, ranges
from 5-15 days in humans, It is estimated that 1 in 150
people who are infected with WNV will required hospitalization.
Of the over 4,000 confirmed human cases of WNV in the U.S.
in 2002, 6% died. The elderly are particularly susceptible
to clinical illness caused by WNV. There is no specific
treatment for infection with WNV, although supportive care
is important.
WHICH ANIMALS GET WEST NILE VIRUS?
An infected mosquito can bite any animal, but not all animals
will become infected. The disease most often affects birds,
but occasionally causes disease in other animals as well.
Birds - Wild birds are the
animals from which the mosquito vector primarily acquires
the virus. Infection has been reported in more than 100
bird species. Although many birds that are infected with
WNV will not appear ill, WNV infection can cause serious
illness and death in some birds. The most severe illnesses
are seen among the corvid birds, which include crows, jays,
ravens, and magpies. American crows constitute the majority
of birds reported dead due to WNV.
Horses - Like people, most
horses bitten by mosquitoes will not become sick with WNV.
However, of those that do, signs may include stumbling,
circling, hind leg weakness, inability to stand, muscle
tremors, and death. A vaccine to prevent WNV illness in
horses is available from your veterinarian. WNV vaccine
and other vaccines against mosquito-borne diseases (western
equine encephalitis and eastern equine encephalitis) should
be given in the early spring. For more information on WNV
and horses, please visit the website: http://www.cdfa.ca.gov/ahfss/ah/wnv_info.htm.
WEST NILE VIRUS CONTROL
To decrease exposure to mosquitoes and the
infections they may carry:
- Avoid spending time outside when mosquitoes
are most active, especially at dawn and dusk.
- When outdoors, wear long pants, long sleeve
shirts, and other protective clothing.
- Apply insect repellent according to label
instructions.
- Make sure that doors and windows have tight
fitting screens. Repair or replace screens that have tears
or holes.
- Eliminate all sources of standing water
on your property that can support mosquito breeding.
- Contact your local mosquito and vector control
agency if there is a significant mosquito problem where
you live or work.
- Mosquito
Fish: Defense from Mosquitoes
WHAT
IS THE CALIFORNIA WEST NILE SURVEILLANCE PROGRAM?
The California Department of Health Services
(DHS) has overseen a statewide mosquito-borne encephalitis
surveillance program since 1969 for Western equine encephalitis
(WEE), St. Louis encephalitis (SLE), and other viruses.
In 2000, DHS and other agencies expanded the program to
enhance the ability to detect WNV. A protocol to report
and test dead birds was added to the existing surveillance
system for encephalitis cases, mosquito testing, and monitoring
of sentinel chickens.
Encephalitis Case Surveillance
DHS tracks cases of human, horse, and ratite (e.g., emu,
ostrich) encephalitis. The routine testing of encephalitis
cases for WNV assists in the early detection of the virus
in California. Human and animal encephalitis cases are also
routinely tested for WEE and SLE viruses.
Mosquito Testing
Mosquitoes throughout the state are sampled for the presence
of WNV, WEE, and SLE viruses. Local mosquito and vector
control agencies also monitor the abundance and type of
mosquitoes.
Sentinel Chicken Testing
Over 200 chicken flocks are strategically placed throughout
the state and are tested routinely during the mosquito season
to detect evidence of infection from WNV, WEE or SLE viruses.
Dead Bird Surveillance
California began to test dead crows and related birds for
WNV in 2000. Monitoring dead crows and other birds will
help identify where the virus is occurring in the State.
State agencies, private organizations, and individuals participate
in the surveillance program by reporting dead bird sightings.
DHS arrange to collect the dead bird from the location it
was found if WNV testing is appropriate.
WHAT DO I DO IF I SEE A DEAD BIRD?
American Crow - American crows
are found throughout most of California. They have entirely
black plumage, black beak, and black feet. Adult size is
17-21 inches from tip of tail to tip of beak.
If you find a dead bird, particularly a crow,
jay, magpie, or raven, pleases call the number below promptly.
Do not touch the bird. DHS will record all dead bird reports
and will arrange for pickup and laboratory testing for WNV
when appropriate.
Dead
Bird Surveillance and Contact Information:
West Nile
Virus Dead Bird Surveillance Program
Division of Communicable Disease Control
California Department of Health Services
Toll Free Telephone: 877-WNV-BIRD (877-968-2473)
E-mail: arbovirus@dhs.ca.gov
Website: http://www.westnile.ca.gov
Migratory
Birds - Flyway Map
(Migratory birds can expand endemic regions).
|
