Physicians

West Nile Virus - 6/2000

West Nile Virus: Is It Coming Our Way?

In New York City and surrounding counties during the summer and fall of 1999, West Nile Virus (WNV), an arthropod-borne disease, caused 62 cases of encephalitis, including 7 deaths.  Prior to this outbreak, the virus had never before been identified in the Western Hemisphere.  In addition to those human cases, WNV infection was confirmed in hundreds of birds, several horses and other domestic animals.  In February, 2000 WNV was identified in a bird in Baltimore, MD.  In May, it was confirmed in birds in New York and New Jersey, indicating that the virus had survived the winter.  Due to the migratory nature of birds, the Virginia Department of Health has instituted enhanced surveillance for West Nile Virus.

WNV is transmitted by the bite of Culex pipiens mosquito, a common household mosquito that feeds on birds, humans, and domestic animals.   Mosquitoes become infected after feeding on infected birds and then spread WNV to humans, animals and other birds by their bites.  WNV is not spread by person-to-person/animal/bird contact. 

Most people who are infected with WNV have no symptoms or experience mild illness such as fever, headache and body aches before fully recovering.  Some individuals may also develop a mild rash or swollen lymph glands.  However, persons over 50 years of age are at higher risk for developing West Nile encephalitis which can cause permanent neurological damage and death. 

Your part in this surveillance is to have a heightened suspicion for West Nile encephalitis in your patients presenting with signs and symptoms of encephalitis.  The recommended criteria for a suspect case is any adult or pediatric patient with:

• Fever  > 38°C or 100°F, and
• Altered mental status (altered level of consciousness, agitation, lethargy) and/or other evidence or cortical involvement (i.e., focal neurologic findings, seizures), and
• CSF pleocytosis with predominant lymphocyctes and/or elevated protein and a negative gram stain and culture, with or without
• Muscle weakness (especially flaccid paralysis) confirmed by neurologic exam or by EMG.  NOTE: In the New York outbreak, two-thirds of the encephalitis cases were associated with severe muscle weakness.

If you have a patient who meets the above criteria, promptly phone the Virginia Beach Department of Public Health at 518-2745.  A communicable disease nurse will obtain further information and discuss obtaining the appropriate specimens for diagnostic tests.  If you do an LP, freeze 1 ml of CSF.

As a part of surveillance activities, we have also begun testing mosquitoes, the sentinel chicken flocks, and  dead birds for WNV.  We will inform you of any confirmed WNV in the area.  Please call 518-2745 if you have any questions or need additional information about West Nile Virus.