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Vector Borne Infectious Diseases / Viral Infections and Vectors / Mosquito Borne Diseases and Control · Journal article
Infectious Disease Reports · August 31, 2026
Early or partial results. Treat as a signal, not a conclusion.
This scoping review characterizes Powassan virus as an emerging U.S. tick-borne encephalitis threat with rising case incidence (60 cases in 2024), a severe neurological syndrome (10–15% case fatality; lasting sequelae in ~50% of survivors), and a sylvatic transmission cycle involving Ixodes scapularis ticks and small-mammal reservoirs. The authors synthesize surveillance, published literature, and archival data to map clinical features, geographic distribution, and ecological drivers, and conclude that enhanced cross-sector surveillance is urgently needed; however, significant surveillance gaps (only 7 of 48 states reporting) and heterogeneous data sources limit definitive inference.
Scoping review (PRISMA-ScR guideline). U.S. Powassan virus cases reported in surveillance systems and published literature; ecological and zoonotic drivers involving Ixodes scapularis ticks, small-mammal reservoirs, and incidental human spillover; geographic focus on U.S. endemic regions (northeastern, Great Lakes, mid-Atlantic, souther…. United States; cases cluster in northeastern and Great Lakes states; viral evidence extends to mid-Atlantic, southern, and western regions..
U.S. POWV cases increased from fewer than two annually before 2005 to a record 60 in 2024 Neuroinvasive disease carries a 10–15% case fatality rate with lasting neurological sequelae in roughly half of survivors Clinical spectrum spans asymptomatic seroconversion to fatal meningoencephalitis, with prodromal fever, headache, vomiting, and fatigue progressing to encephalitis, seizures, aphasia, cranial-nerve palsies, paralysis, and ataxia
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Clinicians should recognize POWV as a rapidly emerging neurological threat in tick-endemic regions, particularly in older adults presenting with acute encephalitis, meningitis, seizures, or cranial-nerve involvement without rash and unresponsive to antibiotics. The absence of effective antivirals and high neurological morbidity underscore the need for clinical awareness and early supportive care; however, the severe national surveillance gap (only 7 of 48 states reporting) means case numbers likely substantially underestimate true burden.
A scoping review synthesizing surveillance data, published literature, and archival records to characterize an emerging infectious disease threat; descriptive and integrative rather than hypothesis-testing, with no comparative trial or meta-analytic effect size.
As stated by the source record.
Quoted from the source exactly as published.
Clinicians should recognize POWV as a rapidly emerging neurological threat in tick-endemic regions, particularly in older adults presenting with acute encephalitis, meningitis, seizures, or cranial-nerve involvement without rash and unresponsive to antibiotics. The absence of effective antivirals and high neurological morbidity underscore the need for clinical awareness and early supportive care; however, the severe national surveillance gap (only 7 of 48 states reporting) means case numbers likely substantially underestimate true burden.
Graded across the dimensions that decide whether you should act, each from what the source actually supports. There is no single score, and where a dimension was not assessed it says so.
Background: Powassan virus (POWV) is the only tick-borne encephalitis-group flavivirus endemic to the United States (U.S.) and is an increasingly serious public health threat. Reported U.S. cases remain relatively few but have grown steadily—from fewer than two annually before 2005 to a record 60 in 2024—and neuroinvasive disease carries a 10–15% case fatality with lasting neurological sequelae in roughly half of the survivors. Examining POWV through a One Health lens, we conducted a scoping review of its ecological and zoonotic drivers, its interactions with co-circulating tick-borne pathogens, its full clinical spectrum, and its distinction from other tick-borne diseases. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidance, we searched PubMed/MEDLINE, U.S. Centers for Disease Control and Prevention (CDC) surveillance databases, state health-department publications, and vetted public-health news through early 2026. The review was conducted as an AI-integrative partnership among the authors, the Global Infectious Diseases and Epidemiology Online Network (GIDEON) database, and Claude (Anthropic), enabling a synthesis of human-curated archival records collected over six years alongside the published literature; this yielded over 200 sources, almost half unavailable through an AI search alone. Results: POWV is maintained in a sylvatic cycle involving I. scapularis ticks, small-mammal reservoirs, and incidental human spillover. Its clinical spectrum spans asymptomatic seroconversion to fatal meningoencephalitis; prodromal fever, headache, vomiting, and fatigue may progress to encephalitis, seizures, aphasia, cranial-nerve palsies, paralysis, and ataxia—the most severe neurological syndrome among U.S. tick-borne diseases. Cases cluster in the northeastern and Great Lakes states, with older males disproportionately affected, while viral evidence extends to the mid-Atlantic, southern, and western regions. POWV is distinguished by its flaviviral etiology, short (as little as 15 min) transmission window, absence of a characteristic rash, and complete antibiotic resistance. Of the 48 states surveyed, only 7 published POWV data. Conclusions: POWV is an escalating One Health threat driven by expanding vector tick ranges, land-use and climate change, and wildlife–human interface dynamics. Enhanced cross-sector surveillance integrating human, animal, and environmental monitoring, alongside improved public-health data reporting, is urgently needed.
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