Massachusetts Department of Public Health
Arbovirus Weekly Report
Week of September 3, 2024
For additional information regarding this report,
Please contact Ryan McGeown-Conron, DPH Director of Legislative Affairs
Ryan.c.mcgeown-conron@mass.gov
Background information on West Nile virus (WNV) and eastern equine encephalitis (EEE) virus and the
Department of Public Health’s current surveillance and response activities is available through
www.mass.gov/dph/mosquito.
Additionally, please find videos regarding mosquitoes and ticks and how best to protect yourself.
Please feel free to share these resources with your constituents: www.mass.gov/MosquitoesAndTicks.
Season Total Total Positive
Number of Mosquito Samples 7185 WNV –286
Tested EEE – 80
Number of Animals Tested 6 WNV – 0
EEE – 2
Number of People Tested 99 WNV – 4
EEE – 2
Key Talking Points for the public for the week of September 3, 2024:
• Aerial spraying to control EEE vectors in Plymouth County was completed on 8/28/24 and ground
spraying in Worcester County was completed on 8/31/24.
• Elevated risk of human transmission occurs from late August through mid-September.
• Completed Aerial and Ground Spray Maps are be posted here: https://massnrc.org/spray-
map/Region/List
• DPH identified the two EEE human cases in Plymouth and Worcester Counties and two EEE horse
cases in Plymouth County. Risk levels have been raised in communities adjacent to these
detections. DPH has increased mosquito surveillance and testing.
• DPH identified four WNV human cases Hampden, Middlesex, Norfolk, and Suffolk Counties. and
the first EEE horse case in the community of Plymouth.
• DPH has detected 80 positive EEE mosquito samples in Barnstable Bristol, Essex, Middlesex,
Norfolk, Plymouth, and Worcester Counties.
• DPH has detected 282 positive WNV mosquito samples statewide. WNV detections are increasing
in MA and in neighboring jurisdictions.
• DPH is responding to EEE detections in Connecticut, New Hampshire, New York, Rhode Island,
and Vermont with increased surveillance activities.
• 2019 was the first year of a two-year outbreak cycle and was the most active EEE year in
Massachusetts since the 1950s. There were 12 human cases with 6 deaths and nine animal cases.
Six aerial sprays were conducted to reduce risk from EEE.
• In 2023 MDPH identified five WNV human cases and 164 WNV positive mosquito samples.
• DPH began early season EEE surveillance in mid-May and continues surveillance activities this
week to monitor for viral activity. Results from trapping and testing mosquitoes are critical to
 understanding how rapidly the viruses might emerge this year and how widespread it might
become.
• DPH has been working since the end of the last season with partners and stakeholders, most
significantly the Massachusetts Department of Agricultural Resources, to prepare for this season.
• Recommended public health measures include raising awareness among residents and reminding
them that it is important to use mosquito repellents with an EPA-registered active ingredient, use
long sleeves and pants to reduce exposed skin and be aware of mosquito activity around you.
• Regional precipitation events coupled with warm weather are expected to increase abundance of
mosquito vectors for both EEE and WNV.
• Check your risk levels throughout the season by visiting www.mass.gov/dph/mosquito.
• Most human cases of WNV and EEE occur in the months of August and September.
• Remember that several 30 second PSA videos are available for download and use on your website
to help promote prevention activities to your residents. These can be found at
www.mass.gov/mosquitoesandticks.
• Pick a repellent with an EPA-registered active ingredient;
• Use long sleeves to cover up when possible;
• Repair screens;
• Remove standing water to help reduce mosquito populations; and
• Teach children to be aware of mosquito activity around them and avoid it.
Interactive EEE and WNV Mapping
Check risk levels throughout the season by visiting our interactive site https://www.mass.gov/info-
details/massachusetts-arbovirus-update
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EEE/WNV Risk Levels
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 EEE Summary by County
As of: 9/3/24
Note: Municipalities start the season at remote, low or moderate risk depending upon historical
EEE activity:
Human Animal
County Towns at Critical risk Towns at High risk Cases Cases
Barnstable 0 0
Berkshire 0 0
Bristol 0 0
Dukes 0 0
Essex 0 0
Franklin 0 0
Hampden 0 0
Hampshire 0 0
Middlesex 0 0
Nantucket 0 0
Norfolk 0 0
Plymouth 3 1 2
Suffolk 0 0
Worcester 4 3 1 0
Total: 2 2
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 WNV Summary by County
As of: 9/3/2024
Note: All municipalities start the season at low risk for WNV:
Human Animal
County Towns at Critical risk Towns at High risk Cases Cases
Barnstable 0 0
Berkshire 0 0
Bristol 0 0
Dukes 0 0
Essex 0 0
Franklin 0 0
Hampden 1 0
Hampshire 0 0
Middlesex 5 1 0
Nantucket 0 0
Norfolk 3 1 0
Plymouth 7 0 0
Suffolk 1 1 0
Worcester 0 0
Total: 4 0
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Below are important steps families and individuals can take in protecting themselves
and their loved ones from illnesses caused by mosquitoes:
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 2 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 3 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
• Drain Standing Water. Mosquitoes lay their eggs in standing water. Limit the number of
places around your home for mosquitoes to breed by either draining or discarding items
that hold water. Check rain gutters and drains. Empty any unused flowerpots and
wading pools, and change water in birdbaths frequently.
• Install or Repair Screens. Keep mosquitoes outside by having tightly-fitting screens on
all of your windows and doors.
More information is available on the DPH website:
www.mass.gov/dph/mosquito. Information about WNV and Eastern Equine Encephalitis (EEE)
is also available by calling the Epidemiology Program at 617-983-6800.
Also, please find videos regarding mosquitoes and ticks and how best to protect yourself to
share with your constituents: www.mass.gov/MosquitoesAndTicks.
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