MAINE PUBLIC HEALTH ALERT NETWORK SYSTEM

 

 

Maine Department of Health and Human Services

Maine Center for Disease Control and Prevention (Maine CDC)
 (Formerly Bureau of Health)
11 State House Station
Augusta, Maine 04333-0011

Phone 1-800-821-5821 / Fax 207-287-7443

**ADVISORY – Important Information**

 


2006PHADV010

 

TO:                 Infection Control Practitioners, Emergency Departments, Primary Care Association, Maine Hospital Association, Veterinarians, Maine HHS Public Health, Maine HHS Public Health Leadership, State and Federal Agencies, Public Health Nurses                       

 

FROM:           Dora Anne Mills, M.D., M.P.H., Public Health Director           

 

SUBJECT:     Human Arbovirus Update for Healthcare Providers in Maine, June 2006

 

DATE:            June 13, 2006 

 

TIME:            7:00 AM

 

PAGES:          3

 

PRIORITY:    Review

 

 

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Human Arbovirus Update for Healthcare Providers in Maine, June 2006

 

In 2005, two horses, one bird, and one mosquito pool tested positive for Eastern Equine Encephalitis (EEE) in Maine, all in York County.  In the same year, eight birds tested positive for West Nile virus (WNV).  These results are the latest indication that there is a real risk of EEE and WNV transmission from infected mosquitoes to Maine residents.  As the warm season approaches, the Maine CDC is alerting physicians and other healthcare providers of the risk of acquired human EEE and WNV infections, and providing laboratory testing criteria and guidelines. 

 

Clinical Features of Arbovirus Infection

 

EEE:  Symptoms of EEE usually appear 3 to 10 days after the bite of an infected mosquito, and range from mild flu-like illness to encephalitis, coma, and death.  The EEE case fatality rate is about 35%-50%.  It is estimated that 35% of people who survive EEE will have mild to severe neurological deficits.

 

WNV:  The incubation period for WNV in humans ranges from 2 to 15 days.  However, most people infected with WNV do not show any symptoms. Mild WNV infections can cause fever, headache and body aches, often with a skin rash and swollen lymph glands. More severe infections can cause headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, paralysis and, sometimes, death.

 

Risk Groups

 

Human cases of EEE occur relatively infrequently, largely because the primary transmission cycle takes place in swamp areas where human populations tend to be limited.  WNV probably infects more people than is known because about 80% of people infected remain asymptomatic. The following groups of people are at the greatest risk for both EEE and WNV infection:

 

Ø      Residents of and visitors to endemic areas

Ø      People who engage in outdoor work and recreational activities

Ø      Persons over age 50 (EEE and WNV) and younger than age 15 (EEE)

 

Diagnostic Tests for EEE and WNV Infections

 

Clinical Suspicion:  EEE and WNV infections can be suspected based on clinical symptoms and patient history.  Diagnosis relies on a high index of suspicion and on results of specific laboratory tests. EEE, WNV or other arboviral infections should be seriously considered in any individual – but especially those over age 50 or younger than age 15  - who has onset of unexplained encephalitis, meningitis, or high fever in the late summer or early fall.  The local presence of EEE and WNV enzootic activity should further raise the index of suspicion.

 

Laboratory Tests: Laboratory testing is required for a confirmed diagnosis. The most efficient diagnostic methods are listed below:

Ø      Detection of IgM antibody in serum collected 3-10 days after onset of illness (note: if a specimen collected less than 10 days after onset of illness is negative, a convalescent serum should be collected and tested for IgM antibody 2-3 weeks after the first collection date).

Ø      Detection of IgM antibody in cerebrospinal fluid collected 3 to 10 after onset of illness (for persons with neuroinvasive disease).

 

Because some other arboviral infections can cause indistinguishable clinical presentations, public health testing for EEE and WNV infections in Maine is accompanied by tests for the viruses that cause St. Louis Encephalitis and Powassan Encephalitis. Specimens that are positive by IgM at the Maine Health and Environmental Testing Laboratory (HETL) are sent to the federal CDC in Atlanta for confirmatory testing using the plaque-reduction neutralization (PRNT) technique.  PRNT is the current gold standard for ruling out possible false positive results and in distinguishing cross-reactions that can occur between different arboviral infections.

 

Diagnostic testing of serum and cerebrospinal fluid for arbovirus infections is available free of charge through HETL.  To ensure a quicker turnaround time and immediate access to laboratory test results for surveillance purposes, Maine CDC requests that all specimens for arboviral testing be submitted to HETL, rather than commercial laboratories. 

 

For information on obtaining and submitting specimens for diagnostic testing call 1-800-821-5821.