Detailed examination of 23 patients at the Cleveland Clinic revealed that among the earliest symptoms in 26 percent was a rash, which helped distinguish the disease from another rapid-onset paralytic disorder, Guillain-Barre syndrome. Misdiagnosis is still very common for West Nile virus, according to lead study author Lara Jeha, MD. Other early symptoms include low back pain, limb pain, and gastrointestinal complaints, typical of many viral illnesses. All patients developed fever at some point in their illness.
Half the patients developed muscle weakness, which developed rapidly, over the course of three to eight days. For many patients, this progressed to involve all four limbs. In one patient, weakness remained the primary symptom even in advanced disease. Nine patients required mechanical ventilation due to weakness of the breathing muscles. Previous studies had described flaccid paralysis with West Nile virus infection, but details about the various aspects of this weakness were very limited.
Altered mental status (confusion, agitation, lethargy) was seen in three-quarters of the patients, along with a variety of other neurological abnormalities, including tremor and seizures. Patients also developed a variety of biochemical abnormalities seen in laboratory tests, and other problems were detected with neuroimaging.
In addition to the need for ventilation, other serious complications occurred, including rhabdomyolysis (breakdown of muscle tissue) in two patients, and hyponatremia, or severe depletion of salt in the blood, in 30 percent of patients. Three patients died as a result of infection.
"West Nile virus infection can cause significant disability," said Jeha. "As the new season begins, it's important for general physicians to be aware of this disease." Catching it early allows the doctor to deal effectively with complications as they arise, including life-threatening ones, she said.
West Nile virus was first reported in the United States in 1999. In 2001, 66 cases occurred in 10 states and resulted in three deaths. By 2002, it had spread to 44 states, with over 4,000 cases and 284 deaths. The virus is spread by mosquitoes, and infects birds and horses as well as humans. Symptoms of infection occur in approximately 1 percent of infected people. There is not yet a vaccine for humans, nor any specific treatment for viral infection.
The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as stroke, Alzheimer's disease, epilepsy, Parkinson's disease, autism and multiple sclerosis.
For more information about the American Academy of Neurology, visit its web site at http://www.aan.com/professionals/
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Neurology