The article pasted below is from Biomednet's e-zine, "HMS Beagle", issue
90, Nov. 10-23, 2000.

Cindy Willis
willisc at immunex.com
Seattle, WA

***************************************************************
West Nile Virus
Coming to a Neighborhood Near You?

by Daniel Edelstein
Posted November 10, 2000 ? Issue 90



Abstract

Are recent reports that the West Nile
Virus has spread well beyond its origin in New York cause for panic?
Probably
not. The author examines the causes for
the range expansion; surveillance measures; potential for vaccine
development; and risk assessment.



"'Disease spreading throughout more of the
U.S. remains a possibility,' doctors say."

During the last year, from her distant
Washington, D.C. residence, research psychologist Jill Weisberg has gotten
used to
reading headlines referring to West Nile
virus (WNV) in New York, where 11 deaths and other illnesses have been tied
to
the mosquito-spread malady since it was
first detected at the Bronx Zoo after 20 flamingos and pheasants died there
in
the fall of 1999.

"I wasn't very worried about it because it
seemed so far away," she said, while adding
"Washington, D.C. felt like it was pretty
removed from the situation, and I assumed it
might be eradicated for good in New York."

Then, recently, everything seemed to
change. Weisberg, as well as residents throughout
states near New York, saw an
eyebrow-raising news story that got their full attention: two
crows found dead in Washington, D.C.
tested positive as carriers of the virus. Only days earlier, other
WNV-positive
crow were detected for the first time this
year in Maryland and Pennsylvania, while the virus was reported in Virginia
and
New Hampshire within a week after the
Washington, D.C. case.

Those reports, in combination with this
year's tenfold geographic expansion of the
disease beyond its initial detection in
New York, have caused doctors to send their own
new precautionary warnings to the public.
[1]

"I am sure that West Nile virus will
[continue to] spread farther from the northeast U.S.,"
said Robert G. McLean, director of the
United States Geological Survey's National
Wildlife Health Center in Madison,
Wisconsin. McLean's certitude is based on the fact
that "the southern migration of [many]
birds is well underway from Canada through the infected area, as well as
summer-breeding birds in the area [are]
moving to locations in the southern U.S. and farther south to the Caribbean
and
Central and South America."

Adds Ward Stone, New York state's veteran
wildlife pathologist, in a recent Washington
Post article: "Three years from now, I
think it'll be over most of the country. . . . It will
be a national problem."

The latest WNV-positive crows in Maryland
and Washington, D.C. prompted nearby
states such as Virginia to expand their
surveillance. Suzanne Jenkins, assistant state
epidemiologist in Virginia, stated, "I
wouldn't be surprised if it was here now, and we just
haven't found it."

Each week, the National Atlas includes a
new series of maps reporting the ongoing West
Nile Virus surveillance activities led by
the Centers for Disease Control and Prevention
(CDC).

Native birds that have been bitten by
virus-carrying mosquitoes are the primary
transmitters of the virus. These
mosquitoes acquire the virus from other infected birds,
which may circulate the virus in their
blood for a few days. After an incubation period of
10 days to two weeks, infected mosquitoes
can then transmit the WNV in their salivary glands while biting to take
blood.
The process is a continuous natural cycle,
with migrating birds during spring and autumn playing key roles in
spreading
the disease.

Although to date 63 species of birds have
tested disease-positive, crows, despite being
non-migratory on the East Coast, appear to
be major carriers. They are primarily
susceptible due to last year's dry
conditions, which may have weakened their immune
systems. In addition, because crows are
larger than most birds, and growing populations
of them frequent urban areas, detection is
more likely after they are found dead. A
comprehensive list of the 2,370
virus-carrying birds reported to date from eight states is
on the Web.

If the virus - called a flavivirus and
commonly found in Africa, West Asia, and the Middle East - is injected into
a person
by a mosquito, health officials warn that
it takes about a week for the victim to develop symptoms. They can range
from a
mild fever and headache to loss of
consciousness, seizures, weakness on one side of the body, and possible
brain
damage. Children and elderly people are
most at risk.

Stephen M. Ostroff of the CDC concurs that
his staff believes that WNV is here to stay.
"We remain concerned about the potential
for geographic spread of the virus. Already
this year, we have seen its range expand
to Rhode Island, Massachusetts, New
Hampshire, Maryland, Pennsylvania, and
areas of New York state that border Canada (to
the north and west). In late September,
Canadian health authorities reported a provisional
finding of the West Nile virus in a bird
in Windsor, Ontario across from Detroit (though
this finding has not been confirmed by
Canadian national health authorities or in the United States)."

Why is the virus spreading beyond its New
York City "epicenter" of discovery, and why do birds appear to be the
primary carrier? Ostroff suggests that
migrational creatures such as birds are larger threats to spread the
disease than
more sedentary mammals (including humans)
simply because "birds in some of their East Coast locations migrate via
routes other than the eastern flyway. This
raises the potential for the virus to spread into other areas."

For example, migrating songbirds such as
wood-warblers, which have recently left their
East Coast breeding grounds, may spend the
winter on the West Coast, while other
populations may move as far south as
Florida. Some yellow-rumped myrtle warblers
particularly tend to spend the winter as
far west and south as California and Arizona,
while a few woodpecker, hawk, and other
warbler species may also follow similar
migration routes during the non-breeding
season.

Authorities' fears have also been raised
by 19 free-living mammals testing positive in recent weeks (three species
of bats,
a raccoon, an eastern chipmunk, and tree
squirrels in New York). In addition, domestic and pet animals have
contracted
the disease (rabbits, chicken, macaw,
parakeet, and cockatoo), while the virus has also been detected in 16
horses from five
states. Even more problematic this year,
Ostruff believes, is the appearance of the virus in Maryland a month
earlier than
in 1999.

Ostruff, who serves as the lead
investigator and coordinator of the virus coordination
committee comprised of representatives
from the CDC, the Department of Interior's U.S.
Geological Survey (USGS), the
Environmental Protection Agency (EPA), and the U.S.
Department of Agriculture's Animal and
Plant Health Inspection Service
(USDA-APHIS), believes there is no reason
for the general public to panic. Increased
detection of the West Nile virus in 2000,
he advises, may be "an artifact of better
surveillance this year" by people who have
turned in more dead birds for testing by state and federal health agencies.
Several states this year have also opened
special laboratories to test for the virus and hired epidemiologists to
track it.

Broader geographic incidence of the virus
in 2000 may also be due, in part, to the region's extremely wet summer,
which
dramatically boosted mosquito populations.
(The mosquito primarily responsible for transmitting the virus is Culex
pipiens, the northern house mosquito.
Another more efficient mosquito vector of the disease this season has been
Aedes japonicus.)

The good news for people concerned about
contracting the disease is that most people
testing positively for the virus never get
sick. Case-fatality rates range from 3 percent to
15 percent and are highest in the elderly,
according to the CDC's Division of
Vector-Borne Infectious Diseases.

The USGS is working with states to
coordinate a multistate surveillance network aimed at
detecting and monitoring WNV in birds and
identifying local areas of WNV activity.

The USGS is also continuing to test
wild-bird carcasses and tissues submitted by state
public-health and conservation agencies
for WNV. The agency's biological containment
facility in Madison has recently expanded
its WNV surveillance efforts by testing crows
found dead on federal lands and conducting
selective field investigations in support of
local, state, and federal public-health
agencies. In addition, the USDA and state wildlife
agencies are collaborating with the USGS
to conduct active surveillance of resident
wild-bird species to identify local areas
of WNV activity.

Preemptive measures implemented by local
governments have not been welcomed routinely by residents and
environmental organizations. Concerns have
been raised about the risks people, pets, and wildlife face after health
departments have sprayed an insecticide
called permethrin in neighborhoods where WNV-positive birds have been
found.
Like other synthetic pyrethroids,
permethrin is a neuropoison that affects mammals as well as insects,
according to the
World Health Organization.

Particularly at risk when inhaling the
chemical are people with respiratory problems such
as asthma, according to Jay Feldman,
executive director at the Washington, D.C.-based
Beyond Pesticides: National Coalition
Against the Misuse of Pesticides.

He urges states "to design adequate
ecological approaches rather than engaging in crisis
pest management at a high cost to human
health and the environment," adding that the
rates of childhood diseases linked to
chemical exposures, from leukemia to asthma, are
important warning signals in our
pesticide-dependent age.

An ultimate solution against WNV in the
form of a vaccine may be forthcoming. But
don't expect your doctor to be able to
write you a prescription any time soon, says
Thomas Monath.

His Cambridge, Massachusetts-based
company, OraVax, is involved with research and
development of a vaccine that could be
used in high-risk populations - especially among
the elderly - during impending epidemics.
Clinical trials of a live, attenuated vaccine are planned to begin in
around
eighteen months, depending on the progress
of preclinical development.

The drug Ribavirin has recently shown
promise as an inhibitor of WNV replication and
its cytopathic effects in neural cells,
according to an October 2000 Journal of Clinical
Infectious Diseases article. An
intravenous form of this drug is not yet licensed in the
United States, but can be made available
on a compassionate-use basis by OraVax with
approval from the Food and Drug
Administration.

Daniel Edelstein, a science writer
and naturalist, lives in Maryland
on a lake at the edge of a forest
35 miles west of Washington, D.C.

David Barneda is a professional
illustrator.







Endlinks

New York's Deadly Virus May Stage a
Comeback, Origin of the West Nile Virus Responsible for an Outbreak of
Encephalitis in the Northeastern United
States, Isolation of West Nile Virus from Mosquitoes, Crows, and a Cooper's
Hawk in Connecticut, Groups Race to
Sequence and Identify New York Virus, and New York's Lethal Virus Came From
Middle East, DNA Suggests - several recent
articles from Science. Registration required for abstracts; paid
subscription
required for full text.
http://www.sciencemag.org

West Nile Virus - offers fact sheets,
press releases, and links on the virus. From the U.S. Geological Service.
http://www.usgs.gov/west_nile_virus.html

West Nile Virus - provides extensive
information on the virus. From the Centers for Disease Control's Division
of
Vector-Borne Infectious Diseases.
http://www.cdc.gov/ncidod/dvbid/westnile/

What's Going on with the West Nile Virus?
- a gateway to information about the virus. From the Environmental Risk
Analysis Program, Center for the
Environment, Cornell University.
http://www.cfe.cornell.edu/risk/WNVmainpage.html

West Nile Fever - offers an extensive
collection of links. http://www.geocities.com/HotSprings/2188/wnf.html

Pennsylvania's West Nile Virus
Surveillance Program - from the state's Department of Health.
http://www.westnile.state.pa.us/

West Nile Virus - from the New York State
Department of Health, the leading local agency in developing a response
plan
and disseminating information about the
virus. http://www.health.state.ny.us/nysdoh/westnile/index.htm