West Nile virus is carried by mosquitoes; it can infect humans, horses, and birds. Humans get the virus from the bite of an infected mosquito. There is no evidence that the disease can spread from other animals to humans or from person to person. Most infections are mild, causing fever and flu-like symptoms, but severe infections may result in encephalitis (inflammation of the brain), and, rarely, death.
The spread of the disease to humans can be controlled by preventing mosquito bites. Avoid outdoor activities during peak mosquito biting times (dusk to dawn, April through October), use insect repellent and drain standing water where mosquitoes breed. Additional information is available on the websites listed below.
A. West Nile virus is a flavivirus commonly found in Africa, the Middle East and West Asia. It was first detected in the United States in 1999. Since then it has spread to almost every state, although it has not yet been reported in Oregon.
A. West Nile virus is spread by the bite of an infected mosquito. The virus is known to have infected people, birds, horses, cats, dogs and some other animals such as chipmunks, bats, skunks, squirrels and domestic rabbits.
A. No. Of the 53 known mosquito species in the northwest United States, only a small number have the potential to carry West Nile virus. The mosquito species responsible for transmitting the West Nile virus, such as Culex species and Aides species, are not common to wetlands. Instead, they prefer highly organic watery areas, such as leaf-clogged gutters and unattended birdbaths.
A. Current estimates indicate that only about 20 percent of people who become infected will develop any type of illness. Mild symptoms (called West Nile fever) can include fever, headache and body aches, swollen lymph glands, and a skin rash. Severe symptoms (called West Nile encephalitis, meningitis and meningoencephalitis) can include high fever, headache and neck stiffness, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. The incubation period in humans (the time between being infected and the onset of symptoms) is 3-14 days.
A. Preventive measures you can take include using a mosquito repellent containing DEETTM that provides protection for the amount of time you will be outdoors. You should be sure to follow all application instructions to avoid irritating your skin, eyes and mouth, or using too much on young children. When outdoors it’s also a good idea to wear long-sleeved shirts and full-length pants. However, mosquitoes can bite through thin clothing, so you also may want to spray your clothing with a repellent. It’s also a good precaution to place mosquito netting over infant carriers.
A. There currently is no conclusive evidence that West Nile virus can be spread from animals to people. However, you should contact your veterinarian on infection control precautions when caring for a sick animal.
A. Hunters (as well as all other outdoor recreators) may be at risk if they become bitten by mosquitoes in areas where West Nile virus is known to be active. There currently is no conclusive evidence that West Nile virus can be transmitted to humans by consuming infected birds or other animals. However, hunters always should follow the usual safety precautions when handling and cleaning animals to prevent blood exposure to bare hands, and always should follow procedures for fully cooking meat to prevent infections from both viruses and bacteria.
A. You should mmediately report dead birds to your local or state health agency or ODFW office. Those agencies will determine if the situation meets the criteria for testing the birds for the presence of West Nile virus.
A. You can reduce the numbers of mosquitoes in areas where you work or recreate by periodically draining sources of standing water such as flower pots, birdbaths, swimming pool covers, livestock and pet water dishes and bins, and miscellaneous buckets and barrels.
A. Natural wetlands provide many benefits: They improve water quality, reduce floods, and provide a rich and diverse natural habitat. In healthy wetlands, water levels fluctuate, constantly moving water around, which limits mosquito production. Also, birds and insects in a wetland area feed on mosquitoes and mosquito larvae, thereby reducing mosquito numbers. If a wetland is disturbed by humans, or if other life forms are eliminated through the incorrect use of pesticides, it is possible that the numbers of mosquitoes in a wetland actually may increase. Therefore, it is important to preserve the natural balance in a wetland by minimizing use of potentially harmful chemicals.