West Nile Virus-The Eye of the Storm

Abstract

A bstract: West Nile virus (WNV) is an arbovirus that emerged in the United States in 1999 and is migrating westward across the country. It occurs in the late summer or fall when there is an abundance of mosquitoes. Symptoms develop 3-14 days after an infected mosquito bites a person. Most WNV infections are asymptomatic or produce mild symptoms; however, 1 in 150 cases is severe with significant neurological deficits. The virus can attack the anterior horn cells, causing acute flaccid paralysis resulting in a poliomyelitis-like syndrome. Diagnosis is based on history, clinical presentation, and laboratory tests. In the late summer or fall, WNV infections should be suspected in persons with unexplained encephalitis, meningitis, or flaccid paralysis. There is no definitive medical treatment for WNV. Preventive measures are the most effective means to combat the disease. Case StudyMr. R is a 55-year-old construction worker who had been digging ditches much of the summer. Prior to admission, he was struck in the right thoracic region with a back hoe and thrown 10 feet. Mr. R did not lose consciousness, but did experience back pain. He promptly recovered and returned to work. Two weeks later, Mr. R awoke with tingling in his right shoulder and pain radiating down his back. He began developing progressive numbness, tingling, and weakness in his lower extremities. He presented to a chiropractor, who did not do any manipulation but rather referred him to the hospital. By the time he reached the emergency department (ED), Mr. R had difficulty walking. He also explained to the ED staff that he had recently experienced difficulty swallowing and had a hoarse voice.Mr. R's medical history was significant for diabetes mellitus with peripheral neuropathy, as well as hypothyroidism, and a possible bleeding disorder. He had quit smoking 5 years previously after an extensive history of smoking for 35 years.In the ED, Mr. R had diffuse weakness, 4+/5, in his legs and right arm with a C4 sensory level of decreased light touch and pinprick. In addition, he was areflexic, although this may have been secondary to his diabetes mellitus. His vital signs were within normal limits; he was afebrile and his blood pressure was 150/80 mm Hg. At that time, steroids were initiated.Mr. R was experiencing marked weakness, altered sensation, areflexia, and swallowing difficulties. The differential diagnoses were cervical myelopathy secondary to a hematoma resulting from his recent trauma, a herniated disc or a tumor. Cervical stenosis and diabetic neuropathy could have accounted for his extremity weakness and sensory changes, but not his swallowing difficulties. Another possible diagnosis was Guillian-Barré Syndrome.The initial work-up consisted of laboratory studies, lumbar puncture, and magnetic resonance imaging (MRI) of the head and cervical spine. Mr. R's metabolic panel was within normal limits with the exception of a glucose level of 162 mg/dL. The complete blood count was also within normal limits with the white blood count at 7.4 K/UL. Th...