Summer is here, which means mosquitoes are here as well. Arboviral diseases, including eastern equine encephalitis (EEE) and West Nile virus (WNV), are very serious infections that are transmitted by the bite of an infected mosquito. Additionally, Powassan virus is an arboviral disease transmitted by the bite of an infected tick. Although rare, these diseases have potentially severe and even fatal consequences for those who contract them. Maine CDC reminds clinicians of the potential for human disease activity in Maine and to consider testing for arboviral disease in patients presenting with unexplained encephalitis, meningitis or fever (≥100.4°F or 38°C) during the summer and early fall.
EEE and WNV were first detected in Maine in 2001 in birds. In 2009, Maine experienced unprecedented EEE activity with 19 animals and two mosquito pools testing positive. In 2012, Maine reported its first human case of locally-acquired WNV neuroinvasive illness. In 2014, Maine reported its first human case of locally-acquired EEE neuroinvasive illness. Powassan was first identified in Maine in 2000 but is rarely reported; a confirmed case in 2013 was the first reported case in nearly a decade. In 2014, Maine reported EEE in an emu from Cumberland County, 22 mosquito pools from York County and one human from York County.
Many people infected with arboviral illness remain asymptomatic. The following groups of people are at higher risk for clinically significant arboviral infection:
- Residents of and visitors to areas with mosquito or tick activity
- People who engage in outdoor work and recreational activities
- People older than 50 and younger than 15
Additional Information
- For more information on arboviral disease: http://www.maine.gov/dhhs/mecdc/infectious-disease/epi/vector-borne/index.shtml
- HETL Laboratory Submission Sheet: http://www.maine.gov/dhhs/mecdc/public-health-systems/health-and-environmental-testing/micro/documents/wnv-sle-eee.pdf
- Weekly arboviral reports will be posted throughout the season at: http://www.maine.gov/dhhs/mecdc/infectious-disease/epi/vector-borne/arboviral-surveillance.shtml
- Disease consultation and reporting available through Maine CDC at 1-800-821-5821
