Scan: Will there be a case of polio in the USA this year? — In 2026

1. Planner Fable 5.1 · Fermi decomposition + tool plan

Tools chosen: kalshi_direct kalshi_related polymarket_related resolution_source claude_news article_search gdelt_news wikipedia code_execution

Sub-questions (Fermi decomposition)

Has CDC or any state health department reported any confirmed polio case (paralytic or non-paralytic) in the US so far in 2026?
What is the historical base rate of years with at least one reported polio case in the US since 2000 (e.g., 2005 Minnesota, 2013, 2022 Rockland County)?
Have there been any poliovirus wastewater detections in the US in 2025-2026, and do wastewater-only detections count as a 'case' for this market?
What are current US childhood polio vaccination coverage rates and are there communities (e.g., Rockland/Orange County NY, Amish/Mennonite areas) with coverage low enough to sustain transmission?
How is global poliovirus circulation trending in 2025-2026 (WPV1 in Pakistan/Afghanistan, cVDPV2 outbreaks, detections in Europe/Israel/Gaza), affecting importation risk?
Have changes at CDC/HHS or ACIP in 2025-2026 affected polio surveillance, reporting, or vaccination recommendations in a way that alters detection or case probability?

Planner reasoning

Polio cases in the US are extremely rare (last confirmed paralytic case: Rockland County NY, 2022; before that 2013), so the key questions are the base rate, current surveillance signals (wastewater detections, CDC reports), vaccination coverage trends, and how ambiguous cases (e.g., wastewater-only detections, vaccine-derived virus, imported cases) would be treated for resolution. The Kalshi price is the primary anchor, with Polymarket cross-checks and news searches for any 2026 detections.

2. Research Parallel tool calls

tool	status	time	items	summary
kalshi_direct	OK	0.2s	1	## This Market's Kalshi Data In 2026 (KXPOLIO-26-0) - Current price (probability): 12.00% - 7-day price change: +5.00% - 30-day price change: -5.00% - Average daily volume: 61 contracts - Price range: 5.00% - 21.00% - Data points: 58 days
kalshi_related	OK	2.8s	2	2 related markets / summaries. series KXPOLIO: 0 markets (skipped 1 no-signal) \| keyword 'polio': ok \| keyword 'measles case': ok
polymarket_related	OK	0.6s	0	Polymarket search over 2 keyword(s), kept 0 matches. keyword 'polio': 0 markets \| keyword 'poliovirus': 0 markets
resolution_source	OK	5.1s	1	already_resolved=unclear; matches_criteria=False; last_updated=May 9, 2024. The page states no wild polio case has been acquired in the US since 1979, and the last imported wild polio case was 1993. It also notes a July 2022 vaccine-derived poliovirus type 2 case in Rockland County, NY, but no cases
claude_news	OK	24.2s	10	## Findings on US Polio Situation for 2026 No confirmed polio cases in the US in 2026 found: - The United States does not have ongoing transmission of polio, but public health officials must remain vigilant. This CDC-related commentary from March 2026 confirms no active transmission as of tha
article_search	OK	0.8s	29	Fetched 29 unique articles across 4 queries (lookback=120d). 'polio case United States 2026': 10 articles \| 'poliovirus wastewater detection US': 10 articles \| 'polio vaccination coverage decline US counties': 10 articles \| 'CDC polio surveillance ACIP polio vaccine recommendation': 10 articles
gdelt_news	OK	193.9s	10	GDELT: 10 articles across 3 queries (lookback=60d). 'polio United States case': error GDELT rate-limited after retries (429) \| 'poliovirus wastewater': 10 hits \| 'polio outbreak 2026': error GDELT rate-limited after retries (429)
wikipedia	OK	0.4s	3	Fetched 3 Wikipedia entries (1 missing pages).
code_execution	OK	20.9s	0	## Base Rate & Probability Estimates for a US Polio Case in 2026 Historical data (2000–2025, 26 years): - 3 years with at least one reported case/infection: 2005 (MN Amish cVDPV1), 2013 (imported case), 2022 (Rockland County NY paralytic case) Core estimates: - **Empirical base

3. Evidence Brief Sonnet 5 · 7299 chars

# Current state No confirmed or suspected polio case (paralytic or non-paralytic, wild or vaccine-derived) has been reported anywhere in the US in 2026 as of the latest research (~Sept 2026). Kalshi prices this at 12% YES, reflecting elevated background risk (declining vaccination coverage, global cVDPV/WPV1 circulation) rather than any active domestic event. # Timeline of key events - 2022-07: Unvaccinated adult in Rockland County, NY diagnosed with paralytic VDPV2 polio; wastewater surveillance later found VDPV2 in NY state/NYC (confirmed, CDC). - 2022–2023: Wastewater poliovirus surveillance conducted in 7 US jurisdictions following the Rockland case; no wild poliovirus found, only VDPV2 traces (confirmed). - 2024-09 onward: Poliovirus wastewater detections reported in Finland, Germany, Poland, Spain, UK (confirmed, ECDC/Eurosurveillance). - 2026-03-11: CNN/CDC commentary reaffirms no ongoing US polio transmission, but urges vigilance (confirmed). - 2026 (through Sept): GPEI reports 23 WPV1 cases (Afghanistan/Pakistan) and ~35–66 cVDPV2 cases globally year-to-date; no US cases (confirmed). - 2026-06-26: Death of Martha Lillard, last US polio survivor using an iron lung — historical/human-interest, not a new case (confirmed). - 2026-07: US measles outbreak surpasses 2025's 35-year record (2,318+ cases), highlighting broader vaccine-preventable-disease resurgence and declining coverage, though distinct from polio (confirmed). - 2026-08: CDC data shows kindergarten polio vaccine coverage at 92.4%, down 2.6 points since 2019-20; 18 states below 90% coverage (confirmed, CDC/KFF/Georgetown). - 2026 (ongoing): Lancet Public Health review notes cVDPV2 detected in wastewater in Cologne/Bonn, Germany; no analogous new US detection reported (confirmed/reported). # Event Will the US report at least one polio case (any type) in calendar year 2026? # Outcomes to forecast Yes / No # Kalshi market anchor KXPOLIO-26-0 currently trades at **12% YES** (7-day: +5pts, 30-day: -5pts; range 5–21% over 58 days; avg daily volume ~61 contracts — thin but liquid enough to be informative). This is the primary consensus benchmark. # Resolution source CDC clinical overview page (last updated May 9, 2024) confirms no wild polio case acquired domestically since 1979, last imported wild case 1993, and the most recent case overall is the July 2022 Rockland County VDPV2 case. Page contains no 2026-specific case data — not a real-time tracker, so it cannot directly confirm current-year status; treated as background/historical anchor only. # Sub-question answers 1. **Any confirmed 2026 US case?** No — CDC/news searches through ~Sept 2026 find no confirmed or suspected case (claude_news, article_search, resolution_source). 2. **Historical base rate since 2000?** 3 of 26 years (2005 MN Amish cVDPV1, 2013 imported case, 2022 Rockland NY VDPV2) had ≥1 case = ~11.5% empirical base rate (code_execution); Laplace-smoothed ~14%. 3. **2025-26 wastewater detections?** No new US detections reported; recent poliovirus wastewater positives are in Europe (Finland, Germany, Poland, Spain, UK since Sept 2024; Cologne/Bonn 2026) (claude_news, Lancet). Ambiguous whether wastewater-only detection (no clinical case) would satisfy this market's "case" definition — likely would NOT count absent a human case, per market description ("cases of polio," not environmental detections). 4. **Vaccination coverage / low-coverage pockets?** National kindergarten polio coverage 92.4% (2025-26), down from higher pre-COVID levels; 18 states below 90%; coverage fell for 5 of last 6 years (US News/CDC, KFF, Georgetown CCF). Rockland/Orange County NY and Amish/Mennonite communities remain historically under-vaccinated, sustaining reintroduction risk, though no new outbreak confirmed there in 2026. 5. **Global circulation trend?** WPV1 ongoing in Afghanistan/Pakistan (23 cases in 2026 per GPEI); cVDPV2 widespread (35-66 cases globally in 2026, multiple countries incl. DRC, Nigeria); Europe seeing wastewater cVDPV2 detections. Importation risk elevated but not directly tied to any confirmed US event. 6. **CDC/HHS/ACIP changes affecting surveillance?** No direct evidence of ACIP/CDC changes altering polio-specific surveillance in 2026; however, broader vaccine-policy shifts under HHS Secretary RFK Jr. are associated with falling MMR/polio coverage and a record measles resurgence (2,318+ cases in 2026), suggesting a systemic risk environment but no direct polio surveillance change documented. # Key facts (high-confidence, factual) 1. [CDC/resolution_source] Last US polio case: July 2022 Rockland County, NY (VDPV2, unvaccinated adult). 2. [code_execution] 3/26 years since 2000 had ≥1 US case (~11.5% base rate). 3. [KFF/CDC] 18 states below 90% kindergarten polio vaccine coverage in 2025-26; national average 92.4%, declining. 4. [GPEI] 2026 global WPV1 total: 23 cases (Afghanistan/Pakistan); cVDPV2 active in multiple countries. 5. [claude_news] No US wastewater poliovirus detections reported in 2025-2026 (unlike Europe). 6. [article_search] 2026 US measles outbreak is worst since 1991 (2,318+ cases), signaling weakening vaccine-preventable disease control broadly. # Cross-market signals - Kalshi related: "Year without polio before 2030" trades at 7.6% (implies markets see near-term elimination unlikely but slow-moving). - Kalshi related: Measles-average-cases market (≥5000 for Trump term) at 34%, reflecting broader vaccine-preventable disease concern. - Polymarket: No matching polio markets found. - Sportsbook implied: N/A. # Analyst opinions and speculation - News commentary (CNN, Mar 2026) frames CDC messaging as "vigilance" rather than alarm — no imminent outbreak signal. - Public health analysts (Georgetown, KFF) flag declining coverage and rising exemptions as structural risk factors that could eventually enable a case, but no analyst predicts a 2026-specific event. # Directional lean per outcome - **Yes**: Supported by declining vaccination coverage, low-coverage pockets (<90% in 18 states), sustained global WPV/cVDPV circulation, and historical precedent (2022 case triggered by similar conditions). Opposed by: no current detection, no wastewater signal, high thin-tail rarity of actual cases even in bad years. - **No**: Supported by zero confirmed 2026 cases through Sept, no domestic wastewater detections, historical base rate <15%/yr even with degrading conditions. Opposing: elevated risk factors could still produce a late-year surprise (a single imported or Rockland-type case is fast and low-notice). # Gaps / unknowns - No visibility into potential undetected/unreported cases in final months of 2026. - Unclear whether wastewater-only detection (no clinical case) would trigger Yes resolution. - No explicit confirmation CDC surveillance capacity/reporting hasn't been reduced by 2025-26 HHS restructuring. # Calibration anchors - Kalshi current YES price: **12%** (primary anchor). - Historical base rate (2000-2025): ~11.5% empirical, ~14% Laplace-smoothed. - Risk-adjusted model range (accounting for coverage decline/global circulation): ~16-25% central estimate. - Related Kalshi market (elimination before 2030) implies ~7.6% annualized elimination-year likelihood, roughly consistent with current 12% single-year case risk.

4. Forecasters 5 draws · Fable 5.1 + GPT-5.6 Sol

claude-fable-5-1

62% conf

Yes	8%
No	92%

No confirmed or suspected US polio case has been reported through ~Sept 2026, and no domestic wastewater detections have occurred (unlike Europe), so roughly two-thirds of the year has passed with zero signal. The historical base rate is ~11.5% per full year (3 of 26 years since 2000), and even a risk-adjusted annual estimate of 16-25% for declining coverage and global cVDPV2 circulation implies only ~5-8% for the remaining ~4 months. Kalshi's 12% YES appears to under-discount elapsed time, though thin liquidity and the possibility of a fast, low-notice Rockland-type case or late reporting justify staying somewhat above the pure time-prorated figure. Ambiguity about wastewater-only detection counting as a 'case' adds a small tail. I settle at 8% YES.

claude-fable-5-1

58% conf

Yes	8%
No	92%

No confirmed or suspected US polio case has been reported through ~September 2026, and no domestic wastewater detections have occurred in 2025-26 (unlike Europe), so roughly three-quarters of the year has already elapsed clean. The full-year historical base rate is ~11.5% (3 of 26 years since 2000), which pro-rated to the remaining ~3.5 months gives only ~3-5%, though elevated structural risk (kindergarten coverage down to 92.4%, 18 states below 90%, active global cVDPV2/WPV1 circulation, record measles resurgence signaling weakened control) and the possibility of a late-reported case before the Jan 2027 close justify some upward adjustment. Kalshi's 12% YES appears to overweight background risk rather than time-remaining; I shade below the anchor to ~8%, recognizing a single Rockland-type case could appear with little warning.

claude-fable-5-1

58% conf

Yes	8%
No	92%

As of ~Sept 2026 no confirmed or suspected US polio case exists, and no domestic wastewater detections have been reported (unlike Europe), so only ~3.5 months of exposure remain plus a reporting-lag window before the Jan 2027 close. The full-year empirical base rate is ~11.5% (3 of 26 years since 2000), which pro-rated to the remaining period is ~3-4%; scaling up ~1.5-2x for declining coverage (92.4% nationally, 18 states <90%), sustained global cVDPV2/WPV1 circulation, and the possibility of retrospective or late-reported cases gives ~6-9%. Kalshi's 12% YES is the anchor, but thin long-shot markets tend to overprice tail events and the brief surfaces no active signal (no wastewater hits, no suspected cases, CDC messaging is 'vigilance' not alarm), so I shade modestly below the market.

gpt-5.6-sol

72% conf

Yes	8%
No	92%

The Kalshi anchor is 12% YES, but no confirmed or suspected US case and no domestic wastewater detection had appeared through roughly September, leaving only the final months of 2026 for a case to emerge. Declining polio vaccination coverage, under-vaccinated pockets, and continued global WPV1/cVDPV2 circulation preserve a meaningful importation and transmission tail risk. However, the historical 11.5% full-year base rate overstates the remaining-year risk once most of 2026 has passed without a signal, so I move below the market to 8% YES. Uncertainty about delayed reporting and the lack of a real-time resolution tracker prevents a more extreme forecast.

gpt-5.6-sol

68% conf

Yes	9%
No	91%

No confirmed or suspected US case has appeared through roughly September 2026, and the absence of a domestic wastewater signal points toward No. Declining vaccination coverage, under-vaccinated pockets, and continued global WPV1/cVDPV2 circulation preserve a meaningful late-year tail risk for Yes. The historical annual base rate of about 11.5% supports the 12% Kalshi YES anchor, but conditioning on nine case-free months and no warning signal warrants a modest reduction to 9%. Uncertainty remains around delayed reporting, undetected cases, and the market's treatment of ambiguous detections.

6. Final plain mean of 5 draws

8% (64% confidence)

Yes: 8% No: 92%

Mean of 5 draws (0.08, 0.08, 0.08, 0.08, 0.09). No confirmed or suspected US polio case has been reported through ~Sept 2026, and no domestic wastewater detections have occurred (unlike Europe), so roughly two-thirds of the year has passed with zero signal. The historical base rate is ~11.5% per full year (3 of 26 years since 2000), and even a risk-adjusted annual estimate of 16-25% for declining coverage and global cVDPV2 circulation implies only ~5-8% for the remaining ~4 months. Kalshi's 12% YES appears to under-discount elapsed time, though thin liquidity and the possibility of a fast, low-notice Rockland-type case or late reporting justify staying somewhat above the pure time-prorated figure. Ambiguity about wastewater-only detection counting as a 'case' adds a small tail. I settle at 8% YES.

Pipeline Timing

Total pipeline time: 262.4s

Per-tool research timings shown in the Research section above.