Public Health

No symptoms in most people. Most people (8 out of 10) infected with West Nile virus do not develop any symptoms.

Febrile illness (fever) in some people. About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with febrile illness due to West Nile virus recover completely, but fatigue and weakness can last for weeks or months.

Serious symptoms in a few people. About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord).

• Symptoms of severe illness include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.
• Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk for severe illness if they are infected (1 in 50 people). People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.
• Recovery from severe illness might take several weeks or months. Some effects to the central nervous system might be permanent.
• About 1 out of 10 people who develop severe illness affecting the central nervous system die.

Diagnosis

• See your healthcare provider if you develop the symptoms described above.
• Your healthcare provider can order tests to look for West Nile virus infection.

Treatment

• No vaccine or specific medicines are available for West Nile virus infection.
• Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms
• In severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.
• If you think you or a family member might have West Nile virus disease, talk with your health care provider.

Reducing exposure to mosquitos is the best prevention for West Nile Virus:

• Use an approved insect repellent containing picaridin, DEET, oil of lemon eucalyptus (not for children under three), or products that contain the active ingredient IR3535.
• Visit the EPA site to search by product and duration of effectiveness.
• Make sure windows have screens. Repair or replace screens that have tears or holes.
• Eliminate any standing water from your property and dispose of containers that can collect water. Standing water is a violation of the New York City Health Code.
• Make sure roof gutters are clean and drained properly.
• Clean and chlorinate swimming pools, outdoor saunas and hot tubs. Keep them empty or covered if not in use. Drain water that collects in pool covers.

Supportive care remains the mainstay of treatment for WN virus infection.

Supportive therapy may include pain control for headaches; if nausea and vomiting are present, antiemetic therapy and rehydration may be beneficial. Patients with encephalitis should be monitored for signs and symptoms of elevated intracranial pressure and seizures. In some patients, particularly those with poliomyelitis-like symptoms, airway protection and ventilatory support may be needed. In patients with WN fever, there is no clear role for treatments other than supportive care.

Potential Therapeutic Agents

There are certain agents that may be of potential benefit for treatment of patients with WN virus neuroinvasive disease; however, data are conflicting, and the risks and benefits of using one of these agents must be determined on a case-by-case basis. These agents include:

• Corticosteroids – The rationale for corticosteroid therapy in the setting of WNV is to inhibit pro-inflammatory mediators that may contribute to the pathogenesis of WNV in the CNS. Several individual case reports have described clinical improvement after administration of high-dose corticosteroids for a variety of neurological complications of WN virus infection (eg, acute flaccid paralysis, opsoclonus myoclonus ataxia). However, in a nonrandomized series of patients with neuroinvasive disease, no difference was noted in the duration of hospitalization for the 18 patients treated with prednisone or other steroids compared with untreated patients.
• Intravenous immunoglobulin – There is a theoretical benefit of administering intravenous immunoglobulin (IVIG) in patients with WN virus neuroinvasive disease who have humoral deficiencies. In the United States and Europe, high titer neutralizing antibodies have been demonstrated in plasma as a consequence of recurring WN virus outbreaks, and animal studies suggested there may be a potential role for the use of IVIG for the prevention and treatment of WN virus infection.

However, IVIG has been administered to immunocompromised patients with varied outcomes. In, a randomized, placebo-controlled safety trial in 62 patients with neuroinvasive disease (the majority who were immunocompetent) failed to find benefit of a high-titered IVIG derived from Israeli donors, although this trial was designed to determine safety and not efficacy.

Limited data have also suggested a potential benefit of interferon alfa therapy, but interferon should not be used for treatment of WNV infection given the toxicity associated with interferon and the limited data supporting its use. Alfa interferon was found to be effective against WNV in in-vitro and in animal models. In addition, rapid neurologic improvement was demonstrated in two patients with serologically confirmed WNV infection who presented with deteriorating mental status and progression to coma and were treated with standard interferon alfa-2b within 72 hours of presentation. However, it remains unclear if the change in clinical status in these patients was due to interferon or to spontaneous improvement, which has been documented in untreated WNV infection. In addition, another report described two patients who developed WN fever after mosquito exposure while receiving interferon alfa-2b and ribavirin for hepatitis C infection.

 There does not appear to be a role for treatment of WN virus disease with the following agents given lack of efficacy:

• Ribavirin – The antiviral agent ribavirin has demonstrated in vitro activity against WN virus, but therapeutic efficacy has not been demonstrated. Ribavirin increased mortality in Syrian golden hamsters when administered two days after inoculation [3]. In addition, during an outbreak in Israel, ribavirin appeared to be ineffective and possibly detrimental when it was used in an uncontrolled, nonblinded fashion in some patients with WN virus neuroinvasive disease.
• Acyclovir – There does not appear to be a role for acyclovir in the treatment of WN virus infection based upon data from retrospective case series. In one report that included 49 patients treated with acyclovir, the duration of hospitalization did not differ compared with untreated patients [16]. In another series of 165 patients with neuroinvasive disease, 94 patients were treated with acyclovir for a median of eight days, and there was no clinical benefit compared with untreated patients.