Using Digital Mapping
to Combat the West Nile Virus
floods and animal movements are routine targets for digital mapping
at the U.S. Geological Survey.
But in the summer of 2000, few projects are as important as the
work USGS is doing to track and help manage the spread of West Nile
virus, a strain
of encephalitis that in 1999 left 62 people in New York infected
and 7 of them dead.
techniques, USGS is providing critical surveillance
information to the Centers for Disease Control and Prevention, USDAs
Animal and Plant Health Inspection Service, State wildlife agencies,
and State and local health and vector
control agencies. Agencies
in 19 states and localities along the Atlantic and Gulf coasts are
engaged in the effort, linked electronically to the online
interactive and multimedia maps updated regularly by USGS.
a web-based Geographic Information System (GIS) that requires software,
hardware, trained users, analysis, and any amount of raw data on
any subject or a combination of subjects. The purpose is to create
visual displays to highlight issues or problems in this case,
the spread of a life-threatening virus.
West Nile virus
-- first isolated in Africa in 1937 -- had spread by the end of
the century to Israel, Eurasia, Asia and Western
Europe. But the virus had never been seen before in the U.S.
until it surfaced in New York last August.
No one knows
for sure how the West Nile virus made it across the Atlantic. A
specialist in mosquito-borne diseases from the United States Army
Medical Research Institute for Infectious Diseases (USAMRIID)
speculates it may have entered the U.S. last year via an infected
mosquito trapped on a transatlantic flight to New York. "When
the plane landed," he says, "the mosquito who hadnt
eaten for 7 or 8 hours headed for the nearest meal, probably
Virus: Getting it and Getting Rid of It
West Nile virus
is transmitted to humans, crows and other
birds through the bite of an infected mosquito, and there are
three separate species that carry the disease: one species feeds
during the day, while the other two feed during the evening and
at night. Many of the fatalities in New York were senior citizens
who contracted the virus in the evening while working in their gardens.
the virus could pose a real health problem for the United States,
especially for the population most vulnerable to the disease
Americans over 50 and people with weakened immune systems. Public
officials point out that there is no vaccine for West Nile Virus
and no specific treatment. Once West Nile virus has been identified
as a threat in a specific area, the only way to eliminate the disease
is to eliminate the mosquitoes that carry it -- spray.
Mapping to Eliminate the Threat
however, are both difficult and expensive
to implement. And there has never been a need before in the U.S.
to mount a mosquito control program of any size or scope. To ensure
the elimination of infected mosquitoes in a cost-effective way,
communities need to spray the right species of mosquitoes at the
right times and in the right places. Public health officials need
to track the carriers of this virus, its victims, movement, intensity
and potential to understand when and where to spray. And thats
where USGS and its digital mapping capabilities are making a difference.
spread of the virus abated late last fall, areas affected by West
Nile virus included New York, New Jersey, Connecticut and Baltimore
County, Maryland. In the spring of 2000, public health officials
confirmed that mosquitoes carrying the West Nile Virus had successfully
survived winter, and that there was reason to believe that the virus
might have spread southward from New York, carried down the eastern
seaboard by migrating
On July 8,
2000 health officials in New York confirmed that dead crows found
in Long Island and Westchester had tested positive for the West
Nile Virus. Infected birds have also been found this summer in New
Lets Users Follow Progression of WNV
veterinarians and citizens who are interested in tracking West Nile
virus through the rest of the summer and fall or who have
information to share -- can visit the National
Atlas virus page. USGS is advertising the WNV maps as a "new
addition" and says "These maps and charts are designed
to illustrate documented occurrences of WNV over time. Let your
cursor roam over the map and images and enjoy the exploration. The
file sizes of these Shockwave maps range from 100 Kb to 150 Kb."
Atlas will include a new series of maps generated by ongoing
WNV surveillance activities led by the Centers
for Disease Control and Prevention (CDC). Maps are available
in three types of mapping services: online interactive maps (over
100 layers of information), dynamic multimedia maps, and high quality
maps for printing and reproduction. Printable maps which
are updated weekly -- offer users six separate categories of information:
Human cases, veterinary cases, wild bird cases, sentinel flock surveillance,
mosquito surveillance and surveillance area.
Measures You Can Use
and online maps provided by USGS are an excellent resource for health
practitioners and citizens who want to learn more about the disease
and ways to prevent its spread. Until the threat is eliminated,
however, there are precautionary measures every American can and
- WNV is
most dangerous to people
over 50, and individuals with weakened immune systems
adults should use mosquito repellent with a high percentage of
the ingredient known as DEET (up to 30%). Do NOT use repellents
containing DEET or potentially dangerous chemicals on children
or infants without consulting a physician -- parents should consult
a pediatrician regarding appropriate types of mosquito repellent
for children of different ages. Always use mosquito repellent
when working or playing outdoors, at the beach and near any body
that the mosquitoes that carry WNV feed during the day, at dusk
and at night. Wear cool, dark, protective clothing that covers
legs, feet, ankles, etc. Do not wear perfume or other substances
that may attract mosquitoes. Be careful when working in gardens
or around water.
standing or stagnant water.
Check old tires and gutters for standing water and keep animal/pet
dishes inside if possible. If it is impossible to eliminate all
sources of water outdoors, there are chemicals (Mosquito Dunk,
for example) available for use in swimming pools, bird baths and
fish ponds that are often toxic for mosquitoes but harmless to
people, birds and fish.
- Do not
handle dead birds, crows or any other variety, if the cause of
death is not readily apparent. Advise children not to handle dead
officials at the Centers for Disease Control and Prevention
say it is unlikely human beings can contract the West Nile virus
by handling infected birds but the obvious rule of thumb should
be better safe than sorry. If you find a dead crow or other bird
whose cause of death is not apparent, call your public heath department.
Dogs and cats are not carriers of WNV and are not at high risk,
even if they do come in contact with an infected bird.
county and community mosquito control programs. Be responsible
for public health education in your community. Initiate dialogue
at the local level, share information with at-risk populations
all you can about West Nile virus -- how it is spread and what
your community can do to combat it.
of West Nile virus include flu-like symptoms, an abrupt onset
of moderate to high fever and sometimes chills, headache (often
frontal), sore throat, backache, myalgia, fatigue, conjunctivitis,
rash spreading from trunk to extremities and head, nausea, abdominal
pain, diarrhea and respiratory symptoms.
- If you are
bitten by a mosquito, dont panic. The majority of mosquitoes
will not be WNV carriers.
- If you think
you might have contracted West Nile virus, dont panic. Ninety
percent or more infected with the disease recover completely.
Call your physician or public health department and arrange for
the appropriate testing.
- If you
have information or data that might be valuable as surveillance
mapping material, contact the U.S.
Geological Survey or the Centers
for Disease Control and Prevention and ask that your information
be added to their weekly updates. Once WNV has been identified
in a certain area, scientists note that the disease is likely
to reemerge over the course of many years - be aware
and make mosquito control a part of your regular routine every
year during the summer and fall.
For more information
about USGS surveillance contact Linda Glaser at 608-270-2446. For
information on West Nile virus and other wildlife diseases, contact
Robert McLean at the USGS National Wildlife Health Center; 608-270-2401
or visit the website.
To learn more
about USGS research programs and activities, visit the main web
site for USGS.
a writer at the National Partnership
for Reinventing Government, can be reached at 304-728-3051 x255
or by email at email@example.com.