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West Nile Virus

Audubon Society of Portland has been working at both the local and state level to ensure that ecologically sensitive West Nile Virus response policies are adopted. Jump to:

Living with West Nile Virus - An Audubon Society Flyer that provides information about the virus and the best ways to minimize risk.

The Alliance for Sensible Mosquito Management (ASMM) - Information about a Multnomah County Based alliance oppose to the use of pesticides to control adult mosquitoes.


Living with West Nile Virus

by Bob Sallinger

Although West Nile Virus has been present in other parts of the world since the 1937, it did not arrive in North America until 1999 when it was first identified in New York City.

Its sudden appearance and quick spread westward has generated sensational headlines and much interest. In fact the risks present to humans by this virus are very low and can be reduced even further by some easy, common sense steps.

Once established, there is no way to eliminate the virus from a geographic area. West Nile Virus first appeared in Oregon during 2004 and health officials expect to see an increased presence during 20071.

It is important that we understand the risks presented by the virus and how best to reduce our chances of exposure. As in other parts of the world that have been coping with the virus for decades, it is important that we learn to live with West Nile Virus.

Putting West Nile Virus in Perspective: Humans

How much of a risk does West Nile Virus really pose to humans? Since 1999, there have been a total of 23,975 confirmed human cases of West Nile Virus and 962 deaths.

To put this in perspective, more people die of influenza each month, than have died of West Nile Virus during the past eight years2.

The primary mode of transmission to humans is by being bitten by an infected mosquito3. Some species of mosquito do not carry the virus and not everyone who is bitten by an infected mosquito will contract the virus.

Of those who do contract the virus, most will never show any symptoms at all; they will most likely never know that they even had the virus. Twenty percent of humans who become infected will show flu-like symptoms.

One out of 150 people who show flu-like symptoms will develop meningitis or encephalitis. One out of ten people who develop meningitis or encephalitis will die.

To put it another way, if 7,500 people contact the virus, 6000 will never even know they have the virus, 1,500 will show flu-like symptoms, 10 will become seriously ill with meningitis or encephalitis, and 1 person will likely die.

Putting West Nile Virus in Perspective: Domestic Animals

As with humans, domestic animals become infected with West Nile Virus by being bitten by an infected mosquito. West Nile Virus infections in dogs and cats are extremely rare.

Infections of horses and domestic birds are more common. Vaccinations for birds and horses are available. To find out more about vaccinations consult with your veterinarian.

Putting West Nile Virus in Perspective: Wildlife

While West Nile Virus has impacted a wide array of wildlife species, the primary impacts have been on birds. Humans cannot contract West Nile Virus by coming in contact with infected birds.

To date there are at least 250 avian species in the United States that have been documented to have contracted West Nile Virus. Members of the corvid family (crows, ravens, magpies and jays) have been particularly hard hit. Some individuals will recover, but many will die from the virus.

Data are only preliminary, but early indications are that while the immediate arrival of West Nile Virus in a new area can cause temporary reductions in the populations of some species, those populations tend to recover in ensuing years as species build up immunity.

Experts are particularly concerned about threatened and endangered species such as spotted owls and condors whose populations are still relatively small and may have more difficulty recovering from short-term population crashes.

How to Minimize Your Risk

It is neither desirable nor possible to completely eliminate entire mosquito populations, but there are some common sense steps that individuals can take to minimize their risks:

  • Install screens in windows and doorways.
  • When traveling in areas with high densities of mosquitoes, wear long sleeve shirts, long pants and socks. Consider using a mosquito repellent and always read the warning label. For those who camp, it is worth noting that the mosquito species typically associated with wooded habitat are not the ones that have been identified as primary carriers of West Nile Virus.
  • Reduce standing water around your home. Mosquitoes can breed in water left standing for a week or more. Clean rain gutters, cover barrels, remove old tires, empty birdbaths at least once weekly.
  • If you find a bird you believe is sick with West Nile Virus, leave it alone and contact your local Fish and Wildlife Agency or wildlife rehabilitation center. Always wear gloves when handling any wildlife regardless of whether you believe it has contracted West Nile Virus or not.
  • Remember that pesticides are poisons. Far more people become ill from pesticides each year than will be impacted by West Nile Virus. Random use of pesticides will not protect you from West Nile Virus but it will add another unnecessary hazard to your environment.

A Word on Behalf of Mosquitoes

Often lost in the discussion of West Nile Virus is the important role that mosquitoes play in the food web. Not all mosquito species carry West Nile Virus.

All mosquito species do however play a vital role in the survival of a vast array of bird and bat species. We could not eliminate all the mosquitoes even if that was what we desired.

The species of greatest concern is the Culex tarsalis or "house" mosquito commonly associated with urban and suburban areas rather than wetlands and woodlands. These mosquitoes breed in standing water oftentimes found in old tires, catch basins, clogged gutters and open garbage receptacles.

It is by reducing these types of mosquito breeding opportunities around our homes rather than by promoting widespread use of pesticides or elimination of fish and wildlife habitat that we will reduce our greatest risk of exposure.

By observing the prudent measures listed above we can protect ourselves and still appreciate and respect the important ecological role played by the mosquito.

Living with West Nile Virus

The arrival of West Nile Virus in Oregon has generated sensational headlines and a great deal of fear. However, it is a response that is driven more by its sudden arrival and quick spread than by the threat that it poses to human health.

In fact another mosquito borne virus quite similar to West Nile Virus, Saint Lewis Encephalitis, has been among us for more than five decades, but hardly generates any coverage or interest at all.

Many people may recall the blaring headlines and pervasive fear generated by the emergence of tick borne Lyme Disease in the early 1990s.

Today Lyme Disease is still among us, but we have adopted common sense strategies to reduce our exposure and there are few among us who now fear to venture out into the woods.

Ten years from now West Nile Virus will still be among us. However it too, will ultimately become something that we take prudent measures to protect ourselves from but think about rarely.

1During 2004, 5 humans, 23 birds and 32 horses tested positive for the virus in Oregon.
2According to the Oregon Health Services on average 36,000 U.S. citizens die of influenza and pneumonia each year.
3The other modes of transmission include blood transfusion, organ transplant and possibly via breast milk.

Additional Information on West Nile Virus

Oregon Department of Human Services
Centers for Disease Control West Nile Virus
Northwest Coalition for Alternatives to Pesticides
PDF of West Nile Virus Handout


Alliance for Sensible Mosquito Management

A coalition of organizations and residents opposed to the use of harmful pesticides for mosquito control in the greater Portland area 

Position Statement on the Use of Pesticides to Control Adult Mosquitoes

created by:
Portland Audubon Society - Bob Sallinger, Wildlife Care Center Director
Xerces Society for Invertebrate Conservation - Mace Vaughan, Staff Entomologist
Northwest Coalition for Alternatives to Pesticides - Pollyanna Lind, Clean Water Campaign Coordinator
and Portland resident, Debby Schwartz

We, the undersigned, fully support the following statement on the use of pesticides to control adult mosquito populations in the Portland metropolitan region.

Though the relative health risks are very low, we recognize that West Nile virus is a disease with public health related concerns. Thus, we support efforts to reduce urban mosquito populations using effective techniques that do not harm wildlife, water quality, or human and environmental health. Specifically, we applaud Multnomah County’s efforts to decrease the spread of the virus by eliminating unnatural bodies of standing water and educating the community about effective, non-chemical ways of reducing mosquito breeding sites around the home.  

We do not support the use of pesticides for adult mosquito control. The use of pesticides to control adult mosquitoes will not eliminate mosquitoes and thus is not a solution to West Nile virus.  It is the least effective way to manage mosquito populations and presents a risk to both human and environmental health.

The pesticides used for adult mosquito control often pose human health risks such as negative impacts on the respiratory, hormone, and nervous systems, especially to vulnerable populations such as asthmatics, the elderly, children, pregnant or nursing women, and people with suppressed immune systems or chemical sensitivities.

The use of pesticides to control adult mosquito populations is likely to negatively impact insect, fish, bird, reptile, amphibians, and mammal populations, including those that naturally control mosquitoes. In addition to being fatally toxic, they can also impede species survival through subtle impacts on reproduction or development, as well as indirect impacts on food supply.

We strongly encourage Multnomah County to continue to focus on educational outreach and non-chemical reduction of backyard and neighborhood mosquito populations as the best and most effective methods of reducing mosquito populations and protecting the public from West Nile virus. We strongly oppose any move towards the spraying of pesticides for adult mosquito control.

Alliance for Sensible Mosquito Management

  • Portland Audubon Society
  • Northwest Coalition for Alternatives to Pesticides
  • Xerces Society for Invertebrate Conservation
  • Physicians for Social Responsibility, Oregon Chapter
  • OSPIRG (Oregon State Public Interest Research Group)
  • Oregon Sierra Club
  • Portland Metro Pacific Green Party
  • The Interfaith Network for Earth Concerns
  • Oregon Center for Environmental Health
  • Coalition for Anadromous Salmon-Steelhead Habitat
  • Low Income Housing by Native Americans in Portland Northwest Environmental Defense Center
  • Rivers Foundation of the Americas
  • The Willamette Riverkeepers
  • Oregon Ecobuilding Network
  • Oregon Trout
  • Southeast Uplift Neighborhood Program
  • Healy Heights Neighborhood Association
  • Buckman Neighborhood Association
  • Foster-Powell Neighborhood Association
  • Hosford-Abernethy Neighborhood Development
  • Hayden Island Neighborhood Network
  • Sunnyside Neighborhood Association
  • Kerns Neighborhood Association
  • Brooklyn Action Corps
  • Mt. Tabor Neighborhood Association
  • Bridlemile Neighborhood Association
  • Forest Park Neighborhood Association
  • Lloyd District Community Association
  • Hillside Neighborhood Association
  • Irvington community Association
  • Overlook Neighborhood Association                  
  • Coalition for a Livable Future
  • Oregon Wildlife Federation       
  • Richmond Neighborhood Association
  • Roseway Neighborhood Association      

For more information or to sign your organization on to the ASMM Statement contact:  The No Spray Portland Information Line (503) 499-1223

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