Arboviral Disease in New Hampshire: Preparation for the 2014 Season

|June 20, 2014
Related Drugs & Diseases

Arboviruses in New Hampshire (NH) include West Nile virus (WNV) and Eastern equine encephalitis (EEE) virus, both transmitted to humans through the bite of an infected mosquito. In 2013, the first human case of locally acquired Jamestown Canyon virus (JCV) was identified in NH. EEE and WNV are maintained in a bird–mosquito cycle, with humans considered incidental hosts.

NH Division of Public Health Services (NH DPHS) recommends the following:

1. Consider mosquito-borne diseases, including WNV and EEE, in patients with compatible clinical features. Laboratory testing is recommended and may be arranged by calling 1-603-271-4496 during business hours or 1-603-271-5300 after hours. Forms and human testing information are available at

2. Educate patients to take preventive measures, including avoiding mosquito bites by use of protective clothing and insect repellents, and environmental reduction of mosquito populations.

3. Use equine vaccines to protect horses; the vaccines are available for both EEE and WNV. Vaccines are not available for human use.

4. Report all arboviral illnesses, confirmed or suspected, to the NH DPHS within 24 hours at 1-603-271-4496 (after hours, 1-800-852-3345, ext. 5300).


JCV is maintained in a deer–mosquito cycle, and reports of human illness are rare. In NH, the highest risk for human infection occurs from July through October. Year-round transmission is possible in some geographic locations in the United States.

Nationally in 2013, there were 2469 human cases of WNV reported in the United States, including 119 deaths. Neuroinvasive disease (meningitis and/or encephalitis) was recorded in 1267 cases, while 1202 cases were diagnosed with milder West Nile fever. There were 7 human cases of EEE reported in the United States, one of which was in the Northeast.

In NH during the 2013 season, there were 14 WNV-positive mosquito batches, 1 veterinary case of WNV, and 1 human with neuroinvasive WNV disease. There were 24 EEE-positive mosquito batches and 3 EEE-positive animals. No human cases of EEE were reported; the last human case of EEE in NH was reported in 2009.

When to Suspect Arboviral Illness

The incubation period following the bite of an infected mosquito ranges from 3 to 14 days. Most arboviral infections are mild and nonapparent. Mild forms of disease normally present as a febrile illness, but sudden onset of symptoms can be seen with headache, myalgias, and arthralgias. Approximately 20% of those infected with WNV develop a mild illness known as West Nile fever.

The more severe forms of arboviral infection include altered mental status and/or neurological dysfunction (cranial and peripheral neuritis or other neuropathies, including acute flaccid paralysis syndrome). A minority of patients with severe disease develop a diffuse maculopapular or morbilliform rash. Approximately 1 in 150 WNV infections will result in severe neurological disease, with encephalitis more common than meningitis. Older patients are at additional risk of developing severe WNV infections. For EEE, approximately one third of all people who develop clinical encephalitis will die from the disease. Among those who recover, many suffer from permanent brain damage, and severe disease can been seen in any age group, including children.

The typical laboratory findings are normal or elevated total leukocyte counts, lymphocytopenia and anemia, and hyponatremia in peripheral blood. Examination of cerebrospinal fluid (CSF) shows pleocytosis (usually with a predominance of lymphocytes), elevated protein, and normal glucose levels. For about one third of WNV patients, magnetic resonance imaging (MRI) shows enhancement of the leptomeninges, the periventricular areas, or both, while MRI of EEE patients often reveals abnormalities of the basal ganglia and thalami.

Treatment is supportive, often involving hospitalization, intravenous fluids, respiratory support, and prevention of secondary infections for patients with severe disease.

When to Report Suspected Cases of Arboviral Illness

Clinicians, hospitals, and laboratories should report within 24 hours any patient meeting the following criteria:

1. Any patient with encephalitis or meningitis from July through November who meet criteria a, b, and c below without an alternative diagnosis:

a. Fever >38.0°C or 100°F, and

b. central nervous system involvement, including altered mental status (altered level of consciousness, confusion, agitation, lethargy) and/or other evidence of cortical involvement (eg, focal neurologic findings, seizures), and

c. Abnormal CSF profile suggesting a viral etiology (a negative bacterial stain and culture) showing pleocytosis with predominance of lymphocytes. Elevated protein and normal glucose levels.

How to Report Suspect Cases of Arboviral Illness

All suspected arboviral cases should first be reported to the NH DPHS by telephone. A completed case report form must be faxed to the NH (1-603-271-0545) and a copy must be submitted with the laboratory specimen(s) to the NH Public Health Laboratories. DPHS staff members are available 24/7 to help determine if the clinical presentation meets the case criteria for viral meningoencephalitis and whether further testing would be appropriate. Specimen submission guidelines are available at the end of this PDF file.

For additional information on arboviral illness and maps of recent activity, please visit the NH Department of Health and Human Services Web site.

Fact sheets on WNV and EEE are also available.

For additional information on WNV and EEE:

NH Department of Health and Human Services Web site

Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases Web site

If you or other healthcare providers have questions, please call the Bureau of Infectious Disease Control at 1-603-271-4496 or 1-800-852-3345, extension 4496, during business hours (8 am to 4:30 pm). Nights or weekends call the New Hampshire Hospital switchboard at 1-800-852-3345, extension 5300, and request the Public Health Professional on call.

Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:


All material on this website is protected by copyright, Copyright © 1994-2016 by WebMD LLC. This website also contains material copyrighted by 3rd parties.