West Nile Virus is a antigenic complex virus found both in tropical and temperate regions. It is known to mainly infect birds, but is also known to infect humans, horses, cats, dogs, skunks, squirrels, chipmunks, rabbits, alligators, and crocodiles. Infected mosquitoes are the main source of human infection. In humans, 90% of West Nile infections go without any symptoms.
West Nile Virus affects humans in 1 of 3 ways. Some people infected with West Nile Virus have an asymptomatic infection, which means they show no symptoms. The second form is a mild febrile syndrome called West Nile Fever. Febrile is a common medical sign characterized by an elevation of temperature above the normal range due to an increase in the body temperature set-point. This increase in set-point triggers increased muscle tone and shivering.
This stage has an incubation period of 2 to 8 days followed by fever, headache, chills, excessive sweating, weakness, swollen lymph nodes, drowsiness, pain in the joints and symptoms like those of influenza or the flu. On occasion there is a short-lived rash and some patients experience gastrointestinal symptoms including nausea, vomiting, loss of appetite, or diarrhea. Symptoms are generally resolved within 7 to 10 days, although fatigue can persist for some weeks and lymph nodes can stay swollen for 2 or 3 months.
The third is a neuroinvasive disease termed West Nile meningitis or encephalitis. Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include fever, headache, confusion, drowsiness, and fatigue. More advanced and serious symptoms include seizures or convulsions, tremors, hallucinations, and memory problems. This stage leads to long hospital stays and unfortunately death some of the time.
There is not a human vaccination available yet, though there is extensive research in the field. There are however vaccinations for horses. Check with your vet for more information on that. West Nile control is achieved through mosquito control, by elimination of mosquito breeding sites, larviciding active breeding areas to kill larva and encouraging personal use of mosquito repellents. The public is also encouraged to spend less time outdoors, wear long covering clothing, and apply a bug repellant that contains DEET. There are also organic repellant options available.