The number of human West Nile virus (WNV) cases in Massachusetts has increased to 24 with the addition of ten additional cases reported Friday.
“We’ve seen four times more West Nile virus human cases this year in the Commonwealth than last year,” said Public Health Commissioner Monica Bharel, MD, MPH. “It is important that we continue to remember that even with the start of fall and its cooler temperatures, mosquito season is not yet over.”
Massachusetts reported six human WNV cases in all of 2017, according to the Centers for Disease Control and Prevention.
“People’s minds are not always on mosquito-borne disease risk at this time of the year,” said Massachusetts Department of Public Health (DPH) State Epidemiologist Dr. Catherine Brown. “However it is not unusual to see people get infected in October – and in fact the latest WNV case we have ever had got sick on November 5.”
WNV is usually transmitted to humans through the bite of an infected mosquito. While WNV can infect people of all ages, people over the age of 50 are at higher risk for severe disease. Most people infected with WNV will have no symptoms. When present, WNV symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur.
As of September 18, 2018, a total of 47 states and the District of Columbia have reported West Nile virus infections in people, birds, or mosquitoes in 2018. Overall, 1,077 cases of West Nile virus disease in people have been reported to CDC. Of these, 608 (56%) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 469 (44%) were classified as non-neuroinvasive disease.
In related news, DPH announced this week that Eastern Equine Encephalitis (EEE) virus has been detected in a mosquito in Massachusetts for the first time this year.
The mosquito samples were collected on September 17 in the town of Lakeville in Plymouth County. This single finding does not indicate elevated risk from EEE at this time, but personal protection from mosquitoes remains a high priority. Mosquito trapping and testing will continue in the area to monitor risk.
There have been no human cases of EEE so far this year and none acquired by a Massachusetts resident in 2017.
DPH offers the following preventive measures for the public to take:
Avoid Mosquito Bites
Apply Insect Repellent when Outdoors. Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)] or IR3535 according to the instructions on the product label.
DEET products should not be used on infants under two months of age and should be used in concentrations of 30% or less on older children. Oil of lemon eucalyptus should not be used on children under three years of age.
Be Aware of Peak Mosquito Hours. The hours from dusk to dawn are peak biting times for many mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning.
Clothing Can Help Reduce Mosquito Bites. Wearing long-sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin.
Mosquito-Proof Your Home
Install or Repair Screens. Keep mosquitoes outside by having tightly-fitting screens on all of your windows and doors.
Protect Your Animals
Horse, llama and alpaca owners should keep animals in indoor stalls at night to reduce their risk of exposure to mosquitoes. Owners should also speak with their veterinarian about mosquito repellents approved for use in animals and vaccinations to prevent WNV and EEE. If an animal is suspected of having WNV or EEE, owners are required to report to DAR, Division of Animal Health by calling 617-626-1795 and to the Department of Public Health (DPH) by calling 617-983-6800.
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