West Nile Virus Questions and Answers

Q: Placer Mosquito Abatement District plans to do truck-mounted ground spraying. What chemical is the District using to spray?

A: For truck-mounted ULV adulticiding or fogging, the District will be using Pyrenone 25-5 under a public health label. The active ingredients are pyrethrin (Pyrethrins are natural insecticides produced by certain species of the chrysanthemum plant) and piperonyl butoxide (a chemical synergist that makes the pyrethrin more effective). We will be applying Pyrenone 25-5 in from trucks in an Ultra-Low Volume (ULV) fog at a rate of 0.87 ounces per acre (less than 2 Tablespoons per acre).

Q: Should I cover my car and/or outdoor furniture?

A: There is no need to cover your car or outdoor furniture. This is an Ultra-Low Volume (ULV) application that suspends the mosquito adulticide in a very fine mist. It persists for less than an hour, and breaks down rapidly when exposed to air or sunlight, and does not leave a residue.

Q: What do I do with my outdoor pets (dog, cat, birds, koi pond)?

A:There is no need to take special precautions with your pets or fish ponds.

Q: Why are they spraying only in south Roseville?

A: The Placer Mosquito Abatement District is only conducting truck-mounted fogging where our surveillance demonstrates that the treatment is needed, and where it will be effective. The District uses many criteria to determine what areas will be fogged for adult mosquitoes, including mosquito trap counts, mosquito infection rates, dead bird reports, sentinel chicken results, human and equine cases of West Nile virus infection, temperature, and other weather-related factors.

Q: Why aren’t they spraying in other areas? When will the rest of Roseville be sprayed?

A: If surveillance shows that it is necessary and will be effective, then the Placer Mosquito Abatement District may treat other parts of Placer County by truck-mounted fogging. The District uses many criteria to determine what areas will be fogged for adult mosquitoes, including mosquito trap counts, mosquito infection rates, dead bird reports, sentinel chicken results, human and equine cases of West Nile virus infection, temperature, and other weather-related factors.

Q: How do I get on the "No Spray" list?

A: Any residents of Placer County wishing to be placed on the No Spray list should email their name, telephone number (including area code), and complete physical address (including city and ZIP code) to the Placer Mosquito Abatement District at pminfo@placermosquito.org or telephone the District at (916) 435-2140. If residents do not provide their COMPLETE address and phone number, and the District is unable to locate their residence, then their address will not be added to the No Spray list.

Q: Are the City's golf courses and all of the city parks being sprayed?

A: The Placer Mosquito Abatement District regularly inspects and – when necessary – treats for larval mosquitoes in standing water sources throughout Placer County, including parks, greenbelts, open spaces, golf courses, wetlands, and catch basins. About 95% of the mosquito control work is directed at the immature stage of the mosquito, when they are confined to standing water sources. By targeting the immature stage of the mosquito, the District can use very specific products like Bacillus thuringiensis israeliensis (B.t.i.), Bacillus sphaericus, and methoprene that prevent the immature mosquitoes from developing into biting adults but do not affect other animals that live in or drink the water (such as frogs, fish, birds, pets, and livestock). Less than 5% of the mosquito control work is directed at the adult stage of the mosquito, but when our surveillance shows that it is necessary and will be effective, then the District will fog for adult mosquitoes using hand-held or truck-mounted Ultra-Low Volume (ULV) fogging with a pyrethrin product at a rate of less than 1 ounce per acre.

Q: What else does the Placer Mosquito Abatement District do to reduce mosquitoes?

Conduct an aggressive program to combat mosquitoes. No current plans to conduct aerial spraying in the residential areas of the county.

Conducts spraying in agricultural areas of Placer County from June to September to prevent mosquito migration to residential areas.

Records of more than 9,000 mosquito breeding sources in the county.

Conducts routine sampling of mosquitoes and adds sources as they are discovered.

Runs ongoing sampling and testing for several viruses is ongoing function, enabling officials to know where the mosquito activity is located, but where it is moving.

Q: How many humans and other species have been affected by WNV in Placer County?

A: As of August 30, 2005, the current year's totals for Placer County WNV include:

11 Humans

14 Horses

2 Dead squirrels

65 Dead birds

12 mosquito pools (a collection of about 50 mosquitoes that are tested together)

Five sentinal chicken flocks

There is significant WNV activity in neighboring Sacramento County, where the Sac/Yolo Vector Control District is conducting aerial spraying.

Q: How are people affected by West Nile virus?

A: Most people who are infected will never know it

80 percent don’t have symptoms.

Of the 20 percent that do have symptoms, most are mild- to moderate-flu like symptoms

1 of 150 who are infected will get seriously ill

How is West Nile virus transmitted?

Mosquito bite - Most people get WNV this way!

Blood transfusion (donated blood routinely tested)

Organ transplant

Mother to child, during pregnancy

Casual contact does not spread the disease

Q: How long does it take to get WNV? What is the timeline for the onset of symptoms?

A: Symptoms will show up 3 to 14 days after bite by infected mosquito.

Q: What is the Treatment for West Nile virus?

A: No specific treatment for WNV infection

Milder cases: fever and aches that pass on their own.

More severe cases: hospitalization may be required for supportive care including intravenous fluids, help with breathing, and nursing care.

Q: What should you do if you think you might be infected with WNV?

A: If you are concerned, seek medical care

In milder cases, disease will usually run its course on its own.

Severe cases: seek medical care

Pregnant and nursing women: Seek doctor’s advice if you believe you may have been exposed to WNV.

Who is at greatest risk?

Elderly

People with chronic medical conditions

People with compromised immune systems

Young and middle-aged people sometimes get WNV - take precautions regardless of age.

Q: How can I avoid getting West Nile virus?

A: WNV is a preventable disease.

Mosquitoes are most active at dawn and dusk: stay inside.

Wear long sleeved shirts and long pants to reduce exposed areas of skin.

Use a repellant when outdoors.

Remove all sources standing water to eliminate mosquito breeding grounds.

Use mosquito-eating fish in animal watering tanks, troughs, ponds.

Fix window and door screens so mosquitoes can’t enter your home or workplace.

Q: Why is it so important to eliminate standing water in my yard?

A: WNV is an urban/suburban disease. Mosquitoes that carry the disease are well suited to breeding in backyard environments. Mosquitoes need standing water, some heat and about a week to go from egg to adult.

Eliminate sources of standing water

Animal watering containers

Birdbaths

Buckets, tires, pots, and anything that collects and holds water

Plugged drains, gutters

Ponds

Buckets

Wading pools

Boats (covered and uncovered)

Trash and recycling bins

Water that collects in storm drains from landscape over watering

Q: Do Animals get WNV?

A: Birds belonging to the corvid group (crows, ravens, jays, magpies) are especially susceptible

Horses are susceptible and have a 40-50% mortality rate. There is an equine vaccine available. Contact your veterinarian

Dogs and cats rarely become ill when infected with WNV

Q: What have the Placer Mosquito Abatement District and Placer County been doing to prepare for the arrival of West Nile virus?

A: The Placer County WNV Task Force has been meeting for three years. The County is well prepared to deal with the arrival of WNV. The Task Force is comprised of:

Placer Mosquito Abatement District

Placer County Health and Human Services

Placer County Office of Emergency Services

Placer County Agriculture Dept.

Veterinarian Dr. Greg Fellers, Loomis Basin Veterinary Hospital

Placer County Public Information Office

California Dept. of Health Services representative Jim Tucker

Q: Where can I get more information?

A: Placer County web site, www.placer.ca.gov/wnv

Placer Mosquito Abatement District web site, www.placermosquito.org

City of Roseville web site, www.roseville.ca.us

Call the County Health Dept. Information line - 530-889-4001 (English and Spanish)

Call the Placer Mosquito Abatement District - 916-435-2140

Placer County West Nile Virus Statistics

2004 Placer County Statistics:

1 human case

26 equine cases

47 positive dead birds

2004 Statewide Statistics:

Present in all 58 counties

830 Human infections

540 Equine infections

3,232 positive dead birds

2005 Placer County Statistics (8/29/05)

10 human cases

12 equine cases

65 positive dead birds

2005 Statewide Statistics (8/29/05)

Present in 52 counties

370 Human infections

8 fatalities

277 Equine cases

1,734 Positive dead birds

History of the Virus

First appeared in U.S. in 1999 in New York

First seen in California in 2002 (one human case)

2003: three human cases, six counties

2004: 830 human cases, 58 counties

Nationally:

2003: 10,000 human cases 262 deaths 2004: 2448 human cases 84 deaths

Q: What is West Nile virus?

A: West Nile Virus is a flavivirus commonly found in Africa, West Asia, and the Middle East. It is closely related to St. Louis encephalitis virus which is also found in the United States. The virus can infect humans, birds, mosquitoes, horses and some other mammals

Q: What are West Nile encephalitis, West Nile meningitis and neuroinvasive disease and West Nile fever?

A:. The most severe type of disease due to a person being infected with West Nile virus is sometimes called neuroinvasive disease because it affects a person nervous system. Specific types of neuroinvasive disease include: West Nile encephalitis, West Nile meningitis, West Nile meningoencephalitis or flacid paralysis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it. West Nile Fever is another type of illness that can occur in people who become infected with the virus. It is characterized by fever, headache, tiredness, aches and sometimes rash. Although the illness can be as short as a few days, even healthy people have been sick for several weeks.

Q: How long has West Nile virus been in the U.S.?

A: It is not known how long it has been in the U.S., but CDC scientists believe the virus has probably been in the eastern U.S. since the early summer of 1999, possibly longer.

Q: I understand West Nile virus was found in overwintering mosquitoes in the New York City area in early 2000. What does this mean?

A: One of the species of mosquitoes found to carry West Nile virus is the Culex species which survive through the winter, or overwinter, in the adult stage. That the virus survived along with the mosquitoes was documented by the widespread transmission the summer of 2000.

Q: Is West Nile virus now established in the Western Hemisphere?

A: The continued expansion of West Nile virus in the United States indicates that it is permanently established in the Western Hemisphere.

Q: Is West Nile virus in California?

A: Yes, West Nile virus was first reported in Southern California in 2003. In 2004 WNV was detected in all 58 California counties, with 830 humans testing positive. Additionally, 540 horses were detected with the virus and 3,232 birds, 1,136 mosquito pools and 805 sentinel chickens. As of Aug. 9, 2005, there have been 118 human infections, 86 horses, 1,055 dead birds, 598 mosquito pools and 27 mosquito pools this year.

Q: Is the disease seasonal in its occurrence?

A: In the temperate zone of the world (i.e., between latitudes 23.5° and 66.5° north and south), West Nile encephalitis cases occur primarily in the late summer or early fall. In the southern climates where temperatures are milder, West Nile virus can be transmitted year round.

Home > Departments > Health and Human Services > Community Health > Communicable Diseases > West Nile Virus > Common Questions
	West Nile Virus Questions and Answers Q: Placer Mosquito Abatement District plans to do truck-mounted ground spraying. What chemical is the District using to spray? A: For truck-mounted ULV adulticiding or fogging, the District will be using Pyrenone 25-5 under a public health label. The active ingredients are pyrethrin (Pyrethrins are natural insecticides produced by certain species of the chrysanthemum plant) and piperonyl butoxide (a chemical synergist that makes the pyrethrin more effective). We will be applying Pyrenone 25-5 in from trucks in an Ultra-Low Volume (ULV) fog at a rate of 0.87 ounces per acre (less than 2 Tablespoons per acre). Q: Should I cover my car and/or outdoor furniture? A: There is no need to cover your car or outdoor furniture. This is an Ultra-Low Volume (ULV) application that suspends the mosquito adulticide in a very fine mist. It persists for less than an hour, and breaks down rapidly when exposed to air or sunlight, and does not leave a residue. Q: What do I do with my outdoor pets (dog, cat, birds, koi pond)? A:There is no need to take special precautions with your pets or fish ponds. Q: Why are they spraying only in south Roseville? A: The Placer Mosquito Abatement District is only conducting truck-mounted fogging where our surveillance demonstrates that the treatment is needed, and where it will be effective. The District uses many criteria to determine what areas will be fogged for adult mosquitoes, including mosquito trap counts, mosquito infection rates, dead bird reports, sentinel chicken results, human and equine cases of West Nile virus infection, temperature, and other weather-related factors. Q: Why aren’t they spraying in other areas? When will the rest of Roseville be sprayed? A: If surveillance shows that it is necessary and will be effective, then the Placer Mosquito Abatement District may treat other parts of Placer County by truck-mounted fogging. The District uses many criteria to determine what areas will be fogged for adult mosquitoes, including mosquito trap counts, mosquito infection rates, dead bird reports, sentinel chicken results, human and equine cases of West Nile virus infection, temperature, and other weather-related factors. Q: How do I get on the "No Spray" list? A: Any residents of Placer County wishing to be placed on the No Spray list should email their name, telephone number (including area code), and complete physical address (including city and ZIP code) to the Placer Mosquito Abatement District at pminfo@placermosquito.org or telephone the District at (916) 435-2140. If residents do not provide their COMPLETE address and phone number, and the District is unable to locate their residence, then their address will not be added to the No Spray list. Q: Are the City's golf courses and all of the city parks being sprayed? A: The Placer Mosquito Abatement District regularly inspects and – when necessary – treats for larval mosquitoes in standing water sources throughout Placer County, including parks, greenbelts, open spaces, golf courses, wetlands, and catch basins. About 95% of the mosquito control work is directed at the immature stage of the mosquito, when they are confined to standing water sources. By targeting the immature stage of the mosquito, the District can use very specific products like Bacillus thuringiensis israeliensis (B.t.i.), Bacillus sphaericus, and methoprene that prevent the immature mosquitoes from developing into biting adults but do not affect other animals that live in or drink the water (such as frogs, fish, birds, pets, and livestock). Less than 5% of the mosquito control work is directed at the adult stage of the mosquito, but when our surveillance shows that it is necessary and will be effective, then the District will fog for adult mosquitoes using hand-held or truck-mounted Ultra-Low Volume (ULV) fogging with a pyrethrin product at a rate of less than 1 ounce per acre. Q: What else does the Placer Mosquito Abatement District do to reduce mosquitoes? Conduct an aggressive program to combat mosquitoes. No current plans to conduct aerial spraying in the residential areas of the county. Conducts spraying in agricultural areas of Placer County from June to September to prevent mosquito migration to residential areas. Records of more than 9,000 mosquito breeding sources in the county. Conducts routine sampling of mosquitoes and adds sources as they are discovered. Runs ongoing sampling and testing for several viruses is ongoing function, enabling officials to know where the mosquito activity is located, but where it is moving. Q: How many humans and other species have been affected by WNV in Placer County? A: As of August 30, 2005, the current year's totals for Placer County WNV include: 11 Humans 14 Horses 2 Dead squirrels 65 Dead birds 12 mosquito pools (a collection of about 50 mosquitoes that are tested together) Five sentinal chicken flocks There is significant WNV activity in neighboring Sacramento County, where the Sac/Yolo Vector Control District is conducting aerial spraying. Q: How are people affected by West Nile virus? A: Most people who are infected will never know it 80 percent don’t have symptoms. Of the 20 percent that do have symptoms, most are mild- to moderate-flu like symptoms 1 of 150 who are infected will get seriously ill How is West Nile virus transmitted? Mosquito bite - Most people get WNV this way! Blood transfusion (donated blood routinely tested) Organ transplant Mother to child, during pregnancy Casual contact does not spread the disease Q: How long does it take to get WNV? What is the timeline for the onset of symptoms? A: Symptoms will show up 3 to 14 days after bite by infected mosquito. Q: What is the Treatment for West Nile virus? A: No specific treatment for WNV infection Milder cases: fever and aches that pass on their own. More severe cases: hospitalization may be required for supportive care including intravenous fluids, help with breathing, and nursing care. Q: What should you do if you think you might be infected with WNV? A: If you are concerned, seek medical care In milder cases, disease will usually run its course on its own. Severe cases: seek medical care Pregnant and nursing women: Seek doctor’s advice if you believe you may have been exposed to WNV. Who is at greatest risk? Elderly People with chronic medical conditions People with compromised immune systems Young and middle-aged people sometimes get WNV - take precautions regardless of age. Q: How can I avoid getting West Nile virus? A: WNV is a preventable disease. Mosquitoes are most active at dawn and dusk: stay inside. Wear long sleeved shirts and long pants to reduce exposed areas of skin. Use a repellant when outdoors. Remove all sources standing water to eliminate mosquito breeding grounds. Use mosquito-eating fish in animal watering tanks, troughs, ponds. Fix window and door screens so mosquitoes can’t enter your home or workplace. Q: Why is it so important to eliminate standing water in my yard? A: WNV is an urban/suburban disease. Mosquitoes that carry the disease are well suited to breeding in backyard environments. Mosquitoes need standing water, some heat and about a week to go from egg to adult. Eliminate sources of standing water Animal watering containers Birdbaths Buckets, tires, pots, and anything that collects and holds water Plugged drains, gutters Ponds Buckets Wading pools Boats (covered and uncovered) Trash and recycling bins Water that collects in storm drains from landscape over watering Q: Do Animals get WNV? A: Birds belonging to the corvid group (crows, ravens, jays, magpies) are especially susceptible Horses are susceptible and have a 40-50% mortality rate. There is an equine vaccine available. Contact your veterinarian Dogs and cats rarely become ill when infected with WNV Q: What have the Placer Mosquito Abatement District and Placer County been doing to prepare for the arrival of West Nile virus? A: The Placer County WNV Task Force has been meeting for three years. The County is well prepared to deal with the arrival of WNV. The Task Force is comprised of: Placer Mosquito Abatement District Placer County Health and Human Services Placer County Office of Emergency Services Placer County Agriculture Dept. Veterinarian Dr. Greg Fellers, Loomis Basin Veterinary Hospital Placer County Public Information Office California Dept. of Health Services representative Jim Tucker Q: Where can I get more information? A: Placer County web site, www.placer.ca.gov/wnv Placer Mosquito Abatement District web site, www.placermosquito.org City of Roseville web site, www.roseville.ca.us Call the County Health Dept. Information line - 530-889-4001 (English and Spanish) Call the Placer Mosquito Abatement District - 916-435-2140 Placer County West Nile Virus Statistics 2004 Placer County Statistics: 1 human case 26 equine cases 47 positive dead birds 2004 Statewide Statistics: Present in all 58 counties 830 Human infections 540 Equine infections 3,232 positive dead birds 2005 Placer County Statistics (8/29/05) 10 human cases 12 equine cases 65 positive dead birds 2005 Statewide Statistics (8/29/05) Present in 52 counties 370 Human infections 8 fatalities 277 Equine cases 1,734 Positive dead birds History of the Virus First appeared in U.S. in 1999 in New York First seen in California in 2002 (one human case) 2003: three human cases, six counties 2004: 830 human cases, 58 counties Nationally: 2003: 10,000 human cases 262 deaths 2004: 2448 human cases 84 deaths Q: What is West Nile virus? A: West Nile Virus is a flavivirus commonly found in Africa, West Asia, and the Middle East. It is closely related to St. Louis encephalitis virus which is also found in the United States. The virus can infect humans, birds, mosquitoes, horses and some other mammals Q: What are West Nile encephalitis, West Nile meningitis and neuroinvasive disease and West Nile fever? A:. The most severe type of disease due to a person being infected with West Nile virus is sometimes called neuroinvasive disease because it affects a person nervous system. Specific types of neuroinvasive disease include: West Nile encephalitis, West Nile meningitis, West Nile meningoencephalitis or flacid paralysis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it. West Nile Fever is another type of illness that can occur in people who become infected with the virus. It is characterized by fever, headache, tiredness, aches and sometimes rash. Although the illness can be as short as a few days, even healthy people have been sick for several weeks. Q: How long has West Nile virus been in the U.S.? A: It is not known how long it has been in the U.S., but CDC scientists believe the virus has probably been in the eastern U.S. since the early summer of 1999, possibly longer. Q: I understand West Nile virus was found in overwintering mosquitoes in the New York City area in early 2000. What does this mean? A: One of the species of mosquitoes found to carry West Nile virus is the Culex species which survive through the winter, or overwinter, in the adult stage. That the virus survived along with the mosquitoes was documented by the widespread transmission the summer of 2000. Q: Is West Nile virus now established in the Western Hemisphere? A: The continued expansion of West Nile virus in the United States indicates that it is permanently established in the Western Hemisphere. Q: Is West Nile virus in California? A: Yes, West Nile virus was first reported in Southern California in 2003. In 2004 WNV was detected in all 58 California counties, with 830 humans testing positive. Additionally, 540 horses were detected with the virus and 3,232 birds, 1,136 mosquito pools and 805 sentinel chickens. As of Aug. 9, 2005, there have been 118 human infections, 86 horses, 1,055 dead birds, 598 mosquito pools and 27 mosquito pools this year. Q: Is the disease seasonal in its occurrence? A: In the temperate zone of the world (i.e., between latitudes 23.5° and 66.5° north and south), West Nile encephalitis cases occur primarily in the late summer or early fall. In the southern climates where temperatures are milder, West Nile virus can be transmitted year round.