Are Mosquitoes Dangerous in New Hampshire?

The virus is maintained in a bird–mosquito cycle by Culiseta melanura, which breeds in the red maple and Atlantic white cedar swamps characteristic of Rockingham County. Human transmission occurs when bridge vectors — Coquillettidia perturbans, Aedes canadensis, Aedes vexans — feed on both infected birds and people. The CDC reports an approximately 30% case-fatality rate among symptomatic EEE patients. Published 2003–2016 surveillance observed a 41% case-fatality ratio overall, climbing to 64% in patients over 70 (Lindsey NP et al., PMC5953388). Roughly half of survivors sustain long-term neurologic sequelae — seizures, paralysis, cognitive impairment — and many require long-term care. There is no licensed human vaccine and no specific antiviral treatment; care is entirely supportive ICU management. NH EEE history: 2005 (7 cases, 2 deaths — the state's first locally acquired cases in 41 years of surveillance); 2014 (3 cases, 2 deaths); 2015–2023 (no confirmed human cases); 2024 (5 cases, 2 deaths — a 41-year-old Hampstead man, Steven Perry, was the first U.S. EEE death of 2024, dying August 19; a Danville adult died later in October). The highest NH EEE risk is in Rockingham County, with elevated risk in Strafford, southern Merrimack, and eastern Hillsborough counties.

By comparison, Connecticut and Massachusetts have each recorded roughly 150–200+ human cases in the same period. Positive mosquito batches are detected more routinely — the 2022 season produced nine WNV-positive mosquito batches in southern NH. Vectors are Culex pipiens and Culex restuans, which breed in stagnant residential water: catch basins, clogged gutters, neglected containers. Clinically, about 80% of WNV infections are asymptomatic, about 20% produce 'West Nile fever' (fever, headache, rash, fatigue), and fewer than 1% progress to neuroinvasive disease — meningitis, encephalitis, or acute flaccid myelitis. Among neuroinvasive cases, mortality is approximately 10% (CDC), rising to 30–40% in immunocompromised patients. Risk rises sharply with age: people over 60 are several times more likely to develop neuroinvasive disease, and those over 70 are more than six times more likely to be hospitalized. WNV is concentrated in NH's southern tier: Hillsborough, Rockingham, Merrimack, and Strafford counties.

New Hampshire is one of the higher-reporting states in the country for this orthobunyavirus, which is maintained in a mosquito–white-tailed-deer cycle and transmitted primarily by early-season Aedes and Ochlerotatus species after spring snowmelt. NH's first confirmed human JCV case was in 2013; by August 2022, 19 cumulative human cases had been reported, including a 2021 fatal case in Dublin (NH DHHS). Additional cases were identified in 2023 and 2024. Many JCV infections are asymptomatic; when symptomatic, patients develop fever, headache, and fatigue, with roughly half of reported cases requiring hospitalization. Neuroinvasive disease (meningitis or encephalitis) occurs in a meaningful minority of cases, and deaths, while rare, have been documented in NH. JCV's early-season transmission window (May–June) predates most residents' use of repellents, making it an underappreciated risk.

Their primary vectors — Aedes aegypti especially — cannot survive NH winters. Aedes albopictus (the Asian tiger mosquito) has not established resident populations in the state despite targeted surveillance with BG Sentinel traps; NH winters are colder than the isotherm that supports overwintering in coastal southwestern Connecticut. Pest-control content that names Ae. albopictus as an NH WNV vector is incorrect — NH's WNV vector is Culex pipiens. Cases of dengue, Zika, or malaria diagnosed in NH residents are always travel-imported. Residents returning from Latin America, the Caribbean, sub-Saharan Africa, or Southeast Asia who develop fever within two weeks of return should mention travel history to their provider.

Skeeter syndrome — a large local allergic reaction to mosquito-saliva proteins — causes marked swelling (often several inches across), warmth, redness, itching, and sometimes blistering, appearing within hours of a bite and resolving in 3 to 10 days. It is most common in young children, immunocompromised patients, and people newly exposed to unfamiliar mosquito species. It is frequently misdiagnosed as cellulitis; treatment differs (antihistamines and sometimes oral corticosteroids, not antibiotics). Secondary bacterial infection from scratched bites introduces Staphylococcus aureus and Streptococcus pyogenes, producing impetigo (especially in children), cellulitis, or, in severe cases, MRSA infections. Seek medical attention for expanding redness over several days, pus, red streaking, or fever — these indicate bacterial infection rather than normal bite reaction.