West Nile Virus (WNV) is an emerging infectious disease first discovered in Uganda in 1937. Now commonly found in Africa, West Asia, Europe and the Middle East, it was identified for the first time in the Western Hemisphere in the New York City area in 1999. In early spring 2000, it reappeared in birds and mosquitoes and spread to other parts of the eastern United States. By 2004, the virus was found in birds and mosquitoes in every state except Alaska and Hawaii. Experts believe WNV is established as a seasonal epidemic in North America that flares up in summer and continues into fall, and they consider it a threat to public and animal health.

More than 1,100 cases of WNV in humans were reported in the United States in 2012, the highest number of cases reported since it was first detected here. According to the Centers for Disease Control and Prevention, the majority of cases originate in five states: Mississippi, Louisiana, South Dakota and Oklahoma, with almost half reported in Texas.

The virus infects humans, birds, mosquitoes, horses and other mammals such as dogs and cats. Most often spread to humans from the bite of an infected mosquito, the virus passes into a person’s bloodstream, where it may cause serious illness. In a very small number of cases, WNV has spread through blood transfusions, organ transplants, breastfeeding and even during pregnancy from mother to baby. WNV is not spread through casual contact such as touching or kissing a person with the virus.

Not all mosquitoes carry the virus that causes West Nile, and approximately 80 percent of people infected with it don’t experience any signs or symptoms, or may experience minor ones. Some individuals, such as those over 50, organ transplant recipients and those with weakened immune systems, are at increased risk for severe WNV illness. Laboratory workers, field and clinical workers who examine and perform necropsies on infected birds or handle WNV-infected tissue or fluids are at risk if their skin is penetrated or cut. If you work or spend time outdoors — especially from July through September and particularly in Midwestern and Southern states — you have a greater chance of being bitten by an infected mosquito.

Diagnosis is based on the patient’s clinical assessment, history of present illness, places and dates of travel, activities and epidemiologic history of the location where the infection occurred. Blood work is tested for the WNV antibody. A lumbar puncture may also be performed. A brain CT or MRI may be ordered to check for inflammation of the brain or the tissue surrounding the brain and spinal cord.

Mild symptoms typically develop three to 14 days after an individual has been bitten and may include fever, head and body aches, nausea, vomiting and sometimes swollen lymph nodes or a skin rash on the chest, stomach and back. Symptoms can last from a few days to several weeks.

However, about one in 150 people infected with WNV develop severe illness. Symptoms include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, seizures, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects could be permanent.

In severe cases, the person is admitted to the hospital for supportive care and treatment with intravenous fluids, medications, oxygen, airway management, nutrition and possible assistance with breathing, usually in a critical care unit. Prevention of secondary infections such as pneumonia and urinary tract infection is essential. This disease can be fatal.

Milder cases of WNV improve on their own, and people do not necessarily need to seek medical attention, though they may choose to do so. If you develop symptoms such as severe headaches or confusion, seek medical attention immediately. Pregnant women and nursing mothers are encouraged to talk to their health care providers if they develop symptoms of WNV.

While no vaccine for humans for West Nile virus exists (one is available for horses), scientists are researching a possible vaccine, with several clinical trials under way. The best way to prevent infection is to avoid mosquito bites.

If possible, stay indoors at dusk and dawn when mosquitoes are most active. Wear socks, shoes, long-sleeved shirts and long pants. Loose-fitting, light-colored clothing is best so you can see the mosquitoes on you. Apply mosquito repellent that contains DEET or oil of lemon eucalyptus to exposed skin as well as your clothing. Choose strength based on the number of hours of protection you need; products with more repellent are not stronger, they just last longer. Do not use DEET on infants under 2 months of age. You can use oil of lemon eucalyptus and cover your child’s stroller, playpen or bed with mosquito netting. Do not apply any repellent to children’s hands since they tend to place their fingers in their mouths. Always use repellents as directed.

WAGE WAR ON MOSQUITOES

• Remove items in your yard that collect water (old tires, empty cans, barrels, flower pots).
• Change the water in birdbaths at least once a week.
• Clean a pet’s outdoor water bowl daily.
• Drain unused pools; remove collected water from pool covers.
• Clean clogged gutters.
• Install and repair door and window screens.
• Report dead birds to your local/state health department.

The content of this article is for informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition.