What is West Nile virus?

West Nile Virus was first seen in the U.S. in 1999, in the New York City area (Queens). New Hampshire has had birds test positive in both 2000 and most recently in 2001. It normally lives in birds and it is passed bird to bird by some types of mosquitoes. Occasionally, an infected mosquito will pass the virus to humans or other animals. Most healthy people do not get sick from the virus, but sometimes it can cause a number of symptoms. When a human gets ill from West Nile Virus, they may have symptoms including encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord); encephalitis and meningitis can also be caused by head injury, bacterial infections or most commonly other viral infections.

How do people get the virus?

West Nile virus is spread to humans by the bite of an infected mosquito. When a mosquito bites an infected bird, it becomes infected. You or your child cannot get West Nile virus from a person who has the disease. West Nile virus is not spread by person-to-person contact such as touching, kissing, or caring for someone who is infected.

Can you get West Nile virus directly from birds?

No known transmission has occurred from birds to people. However, since dead birds may have the virus, one should not handle birds with their bare hands. Reporting of dead birds may be done to your local animal control officer or health officer or to the Department of Agriculture. If you plan to handle a dead bird, use gloves to carefully place dead birds in a double plastic bag ("ziplock" best) then hold the bird for official to pick up.

Besides mosquitoes, can you get West Nile virus directly from other insects or ticks?

Infected mosquitoes are the primary known source for West Nile virus transmission to humans. There is no information to suggest that ticks transmit West Nile virus to humans.

Do birds infected with the virus die or become ill?

In the 1999 outbreak and with the current information for year 2000, large numbers of North American crows were observed becoming seriously ill and dying. Many other species, including exotic species at zoos, can get the infection but usually do not die because of it.

Can other animals get sick?

During the years 1999 and 2000, sick and dead cats, rabbits, and horses were laboratory confirmed as being infected with the virus. In addition, dogs, bats, squirrels, raccoons, chickens, ducks, geese, turkeys and many other species of wild and domestic birds, while not clinically ill tested positive for West Nile virus antibodies, thereby, demonstrating they had been infected.

Where did the West Nile virus come from?

Outbreaks of the West Nile virus have occurred before in Egypt, Asia, Israel, South Africa, parts of Europe and Australia. Before 1999, the West Nile virus had never before been found in the western hemisphere including the United States. Plausible explanations are that an imported infected bird or an infected human returning from a country where the virus is common introduced the virus.

Where has the virus been found?

New Hampshire had it's first positive specimens for West Nile Virus reported in August of 2000. August 16, 2001 New Hampshire found it's first positive specimens (birds only) in the communities of Salem and Rollinsford. West Nile virus has been found in the following states to date: Connecticut, Delaware, Florida, Georgia, Louisiana, Maryland, New Jersey, New York, Ohio, Rhode Island, Virginia and the District of Columbia. Positive mosquitoes have been found in: Connecticut, Florida, Maryland, New Jersey and New York. Horse cases have been confirmed in Florida. Human cases have been confirmed in Florida and Georgia. In 2000, West Nile virus was confirmed in mosquitoes, birds or horses in the following states: New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New Jersey, New York, Delaware, Pennsylvania, Maryland, Washington DC, Virginia and North Carolina.

Where in New Hampshire has the virus been found ?

As of 16 August, 2001, two birds (crows) have tested positive. One in the City of Salem and one in the community of Rollinsford. In the year 2000, seven birds (6 crows and 1 robin) found in Manchester (3), Derry, Hampstead, Candia and Newton, have been reported as positive for West Nile Virus. There has not been a case of West Nile virus in humans or mosquitoes.

What are the symptoms of West Nile virus?

Most people who get infected with West Nile virus have no symptoms at all; some can experience mild illness such as a fever, headache and body aches before fully recovering. In outbreaks in other parts of the world, some persons also developed mild rash or swollen lymph glands. In some individuals, particularly the elderly, West Nile virus can cause serious disease that affects brain tissue. At its most serious, it can cause permanent neurological damage and can be fatal. Encephalitis (inflammation of the brain) symptoms include the rapid onset of severe headache, high fever, stiff neck, confusion, loss of consciousness (coma), and muscle weakness. Death may result in some cases.

Is a woman's pregnancy at risk if she becomes infected with West Nile Virus?

There is no documented evidence that a pregnant woman or the fetus are at increased risk due to infection with West Nile virus.

How are West Nile infection and West Nile encephalitis treated?

There are no specific therapies. In more severe cases, intensive supportive therapy is indicated, i.e., hospitalization, intravenous (IV) fluids and nutrition, airway management, ventilatory support (ventilator) if needed, prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.

Is there a vaccine against West Nile virus?

No. Several drug manufacturers have applied to work on a vaccine, but any vaccine will be several years away.

How long does it take to get sick if bitten by an infected mosquito?

Being bitten by an infected mosquito will not necessarily make you sick since most people who are infected with West Nile virus have no symptoms or experience mild illness. If illness were to occur, it would occur within 5 to 15 days of being bitten by an infected mosquito.

I've gotten a mosquito bite. Should I be tested for West Nile virus?

No. Even in areas where West Nile Virus has been detected most mosquitoes are not infected, and currently in New Hampshire their presence has not been reported. Illnesses related to mosquito bites are rare, especially in New Hampshire. However, you should see a doctor immediately if you develop symptoms such as high fever, confusion, muscle weakness, severe headaches, stiff neck, or if your eyes become sensitive to light. Patients with mild symptoms should recover completely, and do not require any specific medication or laboratory testing.

What should a person do if he/she thinks they have West Nile encephalitis?

If a person has signs of encephalitis, with fever, muscle weakness, and confusion, he or she should seek medical care as soon as possible.

Who is at risk for getting West Nile encephalitis after being bitten by an infected mosquito?

Persons older than 50 years of age have the highest risk of severe disease.

What can I do to reduce my risk of becoming infected with West Nile virus?

From June to October, when mosquitoes are most active, take the following precautions:

  • Protective clothing such as long pants, long-sleeved shirts, and socks should be worn if outside during evening, nighttime and dawn hours, because that is the time when mosquitoes are most active and likely to bite.
  • If outside during evening, nighttime and dawn hours, consider the use of an insect repellent containing 10% or less DEET (N, N-diethyl-meta-toluamide) for children and no more than 30% DEET for adults.
  • USE DEET ACCORDING TO MANUFACTURER'S DIRECTIONS:
    • Do not use DEET on infants or pregnant women. (Instead: avoid outdoor activities during peak biting times, wear covering clothing and use netting/screens to preclude mosquito bites.)
    • Do not allow young children to apply DEET themselves.
    • Do not apply DEET directly to children. Apply DEET to your own hands and then put it on the child.
    • Avoid putting on the hands of children or near their eyes and mouth.
    • Do not spray directly on the face, spray into the hands first and then apply to the face.
    • Do not apply to cuts, wounds, or irritated skin.
    • Do not use under clothing.
    • Do not spray DEET-containing products in enclosed areas.
    • DEET is effective for approximately four hours. Avoid prolonged or excessive use of DEET. Use sparingly to cover exposed skin and clothing.
    • Wash all treated skin and clothing after returning indoors.
    • Store DEET out of reach of children.
  • Vitamin B, ultrasonic devices, incense and bug zappers have not been shown to be effective in preventing mosquito bites.

More information on mosquito repellents is available in a technical article for physicians at the American College of Physicians website: Mark S. Fradin, MD. Mosquitoes and mosquito repellents: A clinician's guide. Annals of Internal Medicine, June 1 1998. 128:931-940.

What can I do around my home to help reduce exposure to mosquitoes?

Mosquitoes lay their eggs in standing water. Weeds, tall grass, and bushes provide an outdoor home for the adult mosquito commonly associated with West Nile virus. Mosquitoes can enter homes through unscreened windows or doors, or broken screens. Here are some steps that you can take:

  • Make sure that doors and windows have tight-fitting screens. Repair or replace all screens in your home that have tears or holes.
  • Remove all discarded tires from your property. The used tire has become the most important domestic mosquito producer in this country.
  • Dispose of tin cans, plastic containers, ceramic pots, or similar water-holding containers. Do not overlook containers that have become overgrown by aquatic vegetation.
  • Drill holes in the bottom of recycling containers that are left out of doors. Drainage holes that are located on the sides collect enough water for mosquitoes to breed in.
  • Make sure roof gutters drain properly. Clean clogged gutters in the spring and fall.
  • Tightly screen "rain barrels" to ensure mosquitoes can't deposit eggs in or on water.
  • Clean and chlorinate swimming pools, outdoor hot tubs. If not in use, keep empty and covered.
  • Drain water from pool covers.
  • Aerate ornamental pools or stock them with fish. Water gardens are fashionable but become major mosquito producers if they are allowed to stagnate.
  • Turn over wheelbarrows and change water in bird baths at least twice weekly. Both provide breeding habitat for domestic mosquitoes
  • Eliminate any standing water that collects on your property. Use landscaping as needed. Mosquitoes will develop in any puddle that last more than 4 days.
  • Remind or help neighbors to eliminate breeding sites on their properties.


Please Note: Although certain pesticide products are available for sale in the market place to control mosquito larvae, one must obtain a special permit from the Department of Agriculture, Division of Pesticide Control to be able to apply pesticides to any surface waters in the state of New Hampshire. Questions regarding how to apply for such special permits may best be directed to the New Hampshire Department of Agriculture, Division of Pesticide Control at 603-271-3550.

What is the State doing to address the possible presence of West Nile virus?

The New Hampshire Department of Health and Human Services, along with other City, State and federal agencies, has developed a plan to assess for the presence of West Nile virus and to find and control the kind of mosquitoes known to carry the virus. This plan includes trapping and testing mosquitoes in selected areas throughout the state, testing dead birds and other animals, and human surveillance. If West Nile virus is found, focused and limited applications of pesticides may be needed to prevent the spread to people.

What health risks are posed to people and pets from pesticides?

If the West Nile Virus is detected in New Hampshire and control measures are needed pesticide application will be recommended; the products that will be applied will be used according to integrated pest management guidelines set by the U.S. Environmental Protection Agency. In the small amounts used, these pesticides would pose negligible risks to people and to pets. Residents will learn about spraying schedules through different mechanisms that may include public service announcements, the media, the DHHS /DES websites, a telephone information line and local authorities.

Should I report dead birds?

The Local Animal Control Officers, Health Officers and The Department of Agriculture are taking reports on dead bird sightings within New Hampshire. While we are interested in collecting information about all dead birds as part of our efforts to understand West Nile virus, we may not be testing every dead bird reported, crows are of particular interest. The Department will only be collecting a sample of all the dead birds reported. However, we encourage New Hampshire residents to report all dead bird sightings to assist the department's monitoring efforts.

If you do not receive a phone call from your Animal Control Officer, Health Officer or the Department of Agriculture to arrange pick up or delivery of the dead bird, within 24 hours of making the report or by the next business day, please carefully dispose of the dead bird. West Nile virus has never been shown to spread directly from birds to people, however dead birds should not be handled with bare hands. Bury the dead bird using gloves or a shovel to avoid direct contact.

For more information call the New Hampshire Department of Health and Human Services, West Nile Virus Info line, at (866) 273 - 6453.

For reports of dead birds, please call the Department of Agriculture at (603) 271 -2404 or the Pelham Animal Control Officer at 635-2411.

For health care providers with clinical questions or to report human suspect or probable cases please contact the Bureau of Communicable Disease Control at (800)852-3345 ext. 4496

Information provided by NH Department of Health and Human Services at www.dhhs.state.nh.us. Click here to visit.

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