Scan: Will there be at least 10000 measles cases in the U.S. in 2026?

date	predicted	market price	confidence
2026-08-23	7%	7%	72%
2026-08-10	4%	7%	65%

1. Planner Fable 5.1 · Fermi decomposition + tool plan

Tools chosen: polymarket_direct polymarket_related kalshi_related claude_news article_search gdelt_news wikipedia code_execution

Sub-questions (Fermi decomposition)

What is the current 2026 year-to-date confirmed measles case count on the CDC counter, and what was the weekly pace of new cases over the last 4-8 weeks?
How many measles cases did the US record in 2025 (final CDC count), and what fraction of those came from a single large outbreak (West Texas)?
Are there currently large active outbreaks (e.g., South Carolina, Utah/Arizona, Texas, other states) and are their weekly case counts growing, plateauing, or declining?
Has the US lost (or is it about to lose) measles elimination status due to 12+ months of continuous transmission, indicating sustained endemic spread rather than sporadic imported outbreaks?
What does linear or exponential extrapolation of the 2026 YTD pace imply for the full-year total, and what growth rate would be needed to reach 10,000?
How are the sibling Polymarket/Kalshi threshold markets (e.g., ≥2,000, ≥5,000, ≥10,000 cases in 2026) priced, and is the implied distribution internally consistent?
What are national MMR vaccination coverage trends and any 2026 policy changes (e.g., ACIP/CDC schedule changes, school exemptions) that could increase susceptibility?

Planner reasoning

This is a Polymarket health question about whether the CDC counter will show ≥10,000 confirmed US measles cases in 2026, a threshold far above 2025's ~1,700+ (already the worst since 1992). The key drivers are the current 2026 year-to-date count on the CDC tracker, the trajectory of active outbreaks (e.g., South Carolina, Utah/Arizona, Texas), whether the US has lost elimination status and is seeing endemic spread, and how sibling threshold markets (2,000/5,000/etc.) are priced. I'll anchor on the direct Polymarket price, pull sibling threshold markets, get latest news on 2026 case counts and outbreaks, and use code execution for trajectory extrapolation and historical base rates.

2. Research Parallel tool calls

tool	status	time	items	summary
polymarket_direct	OK	0.4s	1	## This Market's Polymarket Data Will there be at least 10000 measles cases in the U.S. in 2026? - Current price (probability): 7.05% - 7-day price change: +0.50% - 30-day price change: +1.20% - Total volume: $6,525,084 (USD notional) - Price range: 4.50% - 9.05% - Data points: 91 days
polymarket_related	OK	0.7s	0	Scanned 100 active Polymarket markets, kept 0 matches. keyword 'measles': 0 markets
kalshi_related	OK	0.6s	1	1 related markets / summaries. keyword 'measles': ok
claude_news	OK	18.9s	14	Based on my research, here are the key findings: - 2026 YTD case count (as of Sept 10, 2026): As of September 10, 2026, 3,294 cases have been confirmed in 2026, 8% of which required hospitalization . This already exceeds one-third of the way to 10,000. (usafacts.org) - **2026 already surpasse
article_search	OK	1.9s	14	Fetched 14 unique articles across 4 queries (lookback=45d). 'CDC measles cases 2026 United States total': 10 articles \| 'measles outbreak 2026 South Carolina Utah Arizona weekly cases': 10 articles \| 'US measles elimination status lost 2026': 10 articles \| 'MMR vaccination rates decline 2026': 10 ar
gdelt_news	OK	62.3s	20	GDELT: 20 articles across 2 queries (lookback=30d). 'measles outbreak United States 2026': 10 hits \| 'CDC measles case count': 10 hits
wikipedia	OK	0.2s	3	Fetched 3 Wikipedia entries (0 missing pages).
code_execution	OK	43.5s	0	## Quantitative Findings: US Measles Cases ≥10,000 in 2026 Historical base rate (post-elimination era, 2000–2025, n=26 years): - 0 of 26 years (0.0%) have reached ≥10,000 cases since elimination was declared in 2000; max was 2025's ~1,900 cases, followed by 2019's 1,274. - Raw MLE base

3. Evidence Brief Sonnet 5 · 8201 chars

# Current state As of the latest CDC data cited in research (Sept 10, 2026), the U.S. has confirmed **~3,294 measles cases in 2026** — already the worst year since 1991 and far above full-year 2025 (~2,144–2,289 cases). Reaching 10,000 by Dec 31, 2026 requires roughly 4-5x acceleration in the weekly case pace over the remaining ~16 weeks of the year. Polymarket prices this outcome at only ~7%. # Timeline of key events - **2025 (Jan–Aug)**: West Texas/Southwest measles outbreak (Gaines County, TX epicenter) spreads to NM, OK, Kansas; ~750-800 cases, 3 deaths; declared over Aug 18, 2025 (confirmed, Wikipedia/CIDRAP). - **2025 (Oct)–2026 (Apr)**: South Carolina/Spartanburg County outbreak grows to ~997 cases (largest single US outbreak since 2000); declared over April 27, 2026 (confirmed, CIDRAP). - **2025 full-year**: CDC finalizes ~2,144–2,289 confirmed cases (sources vary slightly), 45 jurisdictions, 49 outbreaks (confirmed, AAP/CDC/Wikipedia). - **2026-06-20**: New outbreak begins on Utah-Arizona border in under-vaccinated communities; grows to 680+ cases across 22 of 29 Utah counties by fall (confirmed, CIDRAP). - **2026-07 (mid-July)**: 2026 YTD cases (~2,318) surpass full-year 2025 total (confirmed, multiple sources). - **2026-08-17**: CDC/CIDRAP report "35-year high" in cases (~2,700+) (confirmed). - **2026-08-25**: First two US measles deaths of 2026 reported in Pennsylvania (unvaccinated individuals); Pennsylvania becomes new epicenter, surpassing South Carolina (confirmed, CNN/CIDRAP). - **2026-09 (early)**: CDC declines to add two Pennsylvania measles-associated deaths to official tally pending review; sparks controversy (reported, multiple outlets: NBC10, 6abc, MoneyControl). - **2026-09-10**: CDC/state data shows ~3,294 YTD cases nationally; Pennsylvania at 676, ~38 outbreaks in 2026, 95% outbreak-associated (confirmed, CDC/CIDRAP/USAFacts). - **2026-08 (mid-Aug)**: National verification committee reviews US measles elimination status; forwarding findings to PAHO committee, decision expected November 2026 (reported, STAT News). A Lancet study concludes it is "highly likely" the US will lose elimination status in 2026. # Event Will there be at least 10,000 measles cases in the U.S. in 2026 per the CDC counter? # Outcomes to forecast - Yes (≥10,000 cases) - No (<10,000 cases) # Kalshi market anchor No Kalshi-direct price was returned for this specific ticker; the closest cross-platform anchor is **Polymarket at 7.05% YES** (as of research date), up from a 90-day low of 4.5% and near its 90-day high of 9.05%. 7-day trend +0.5pp, 30-day trend +1.2pp — slow upward drift, $6.5M total volume (high liquidity/confidence). Treat this as the de facto consensus given no distinct Kalshi print was retrieved. # Sub-question answers 1. **YTD count & pace**: ~3,294 cases as of Sept 10, 2026 (CDC/USAFacts); implies an average pace of ~85-90 cases/week over ~37 weeks. Weekly pace has been accelerating with new outbreaks (PA, GA daycare cluster) emerging even as older ones (SC) close. 2. **2025 final count & Texas share**: Final 2025 CDC tally ~2,144–2,289 (sources vary); the West Texas/Southwest outbreak contributed ~750-800 cases (~33-35% of the year's total). 3. **Active outbreaks now**: Pennsylvania (676 cases, growing — added 52 in 2 days as of early Sept), Utah (526-680 cases, plateauing per CIDRAP), South Carolina outbreak declared over (Apr 2026, 670-997 cumulative), plus 38 new 2026 outbreaks including a Georgia/Atlanta daycare cluster. Net: PA growing fastest; SC/Utah stabilizing/declining. 4. **Elimination status**: Not yet formally lost. National verification committee reviewed evidence mid-Aug 2026; referred to PAHO for a November 2026 decision. Lancet study says loss is "highly likely" in 2026 — this is a rumored/anticipated event, not yet resolved. 5. **Extrapolation**: Code-execution analysis shows steady 2025-like pace yields only ~4,000-7,800 full-year cases; reaching 10,000 requires remaining-weeks average to jump ~2.7-4.7x current pace (~4-9% compounding weekly growth) — a high bar exceeding typical outbreak decay dynamics. 6. **Sibling market consistency**: Illustrative sibling-threshold pricing (≥2,000: 55%, ≥5,000: 18%, ≥10,000: 6%) is monotonic and roughly consistent with a power-law tail-decay (~1/3 survival probability per threshold jump); Kalshi sibling market on "avg measles cases during Trump's term ≥5,000" prices 35% (up from 28% a month ago), suggesting some optimism about sustained elevated case counts but not to the 10,000 single-year level. 7. **Vaccination trends**: Kindergarten MMR coverage down from 95.2% (2019-20) to 92.4% (2025-26), ~280,000 kindergartners now under-vaccinated (CDC). No specific 2026 ACIP/policy change was reported in research; decline is gradual/structural rather than a single 2026 event. # Key facts (high-confidence, factual) 1. [USAFacts/CDC] 3,294 confirmed 2026 cases as of Sept 10, 2026. 2. [CIDRAP/AAP] 2025 final total ~2,144–2,289 cases, worst year since 1991 at the time. 3. [Wikipedia/CIDRAP] South Carolina outbreak (997 cases) is largest single US outbreak since 2000; declared over April 27, 2026. 4. [CNN] First 2026 measles deaths (Pennsylvania, unvaccinated) confirmed Aug 25, 2026; later a third PA death (infant) reported Sept 2026. 5. [CDC] Kindergarten MMR coverage fell to 92.4% (2025-26 school year) from 95.2% (2019-20). 6. [STAT News/Lancet] US elimination status review ongoing; PAHO decision expected November 2026. # Cross-market signals - Kalshi related: "Avg measles cases during Trump's term ≥5,000" priced at 35% (up 3pp/7d, 4pp/30d) — implies moderate confidence in sustained multi-year elevated counts, not single-year 10,000. - Polymarket: This exact market at 7.05% YES, gradually rising, high volume ($6.5M) — a credible, liquid consensus. - No sportsbook signal available (not applicable to this event type). # Analyst opinions and speculation - Lancet/PAHO commentary: US "highly likely" to lose elimination status in 2026 — a distinct, lower-bar milestone than 10,000 cases (12 months continuous transmission suffices). - CIDRAP/CBS: Outbreaks framed as "record-breaking," raising narrative salience but not necessarily changing quantitative trajectory toward 10,000. - Code-execution Bayesian estimate: 0/26 years since 2000 have hit 10,000; Laplace-smoothed base rate ≈3.4%; current-pace-adjusted estimate ≈3-8%. # Directional lean per outcome - **Yes (≥10,000)**: Supported by unprecedented 2026 pace (already exceeding 2025 by midyear), multiple simultaneous outbreaks (PA, Utah, GA), declining vaccination coverage, elimination-status loss narrative. Opposed by: no historical precedent even close (max ever ~2,289), extrapolation showing pace would need to nearly 5x, and individual outbreaks typically plateau/decline within weeks (SC already closed). - **No (<10,000)**: Supported by base rates (0/26 years), quantitative extrapolation (linear/steady pace yields 4,000-7,800), historical outbreak dynamics (peak-and-decline pattern), and market pricing consensus (~7% Yes). Opposing: accelerating case counts and new outbreak emergence could still surprise to the upside if a large new event (e.g., major urban spread) occurs. # Gaps / unknowns - No direct Kalshi YES price was retrieved for this specific ticker (relied on Polymarket as proxy). - Exact current weekly case velocity (last 4-8 weeks specifically) not granularly detailed — only cumulative snapshots (2,318 → 2,700 → 2,777 → 2,144-2,289(2025) → 3,294). - CDC vs. state-reported death/case discrepancies (PA controversy) suggest possible undercount/reporting lag risk both ways. - No explicit sibling ≥2,000/≥5,000 Kalshi/Polymarket prices were directly retrieved (code-execution used illustrative figures). # Calibration anchors - Polymarket YES price: **7.05%** (current anchor), range 4.5-9.05% over 90 days. - Historical base rate: 0/26 years (2000-2025) reached 10,000; worst year (2025) ~2,289; 2026 already ~3,294 by Sept — an unprecedented pace but still requiring ~3x acceleration to hit threshold. - Analogous Kalshi sibling market (Trump-term average ≥5,000) priced at 35%, providing a rough upper bound for even lower thresholds.

4. Forecasters Fable 5.1 + GPT-5.6 Sol · in parallel

claude-fable-5-1

78% conf

Yes	4%
No	96%

As of Sept 10, 2026 the CDC counter stands at ~3,294 cases, so reaching 10,000 requires ~6,700 more cases in ~16 weeks — roughly 420/week versus the year-to-date pace of ~85-90/week, a 4-5x acceleration with no historical precedent (0/26 years since 2000 anywhere near 10,000; prior record ~2,289). The fastest-growing outbreak (Pennsylvania, ~676 cases) is large but the biggest outbreaks of this era (SC ~997, West Texas ~800) have plateaued within months, and extrapolation of steady or moderately rising pace yields ~4,000-7,800 full-year cases. The Polymarket anchor at ~7% YES is the consensus; I shade slightly lower because the required compounding weekly growth exceeds typical outbreak dynamics and year-end reporting lag works against the counter, while leaving tail probability for a major urban super-spreading event.

gpt-5.6-sol

74% conf

Yes	6%
No	94%

The 3,294 cases reported through September 10 point toward No because reaching 10,000 would require roughly 6,700 additional cases in about 16 weeks, far above the year-to-date weekly pace. Pennsylvania is growing quickly and vaccination coverage is declining, but Utah is plateauing and South Carolina has ended, making the required nationwide acceleration unlikely. Possible loss of elimination status indicates sustained transmission but is a much lower bar than 10,000 cases, while historical data show no year since 2000 approaching this threshold. I anchor near Polymarket's liquid 7.05% YES consensus and move slightly lower to 6% because quantitative extrapolations generally finish well below 10,000 and outbreak dynamics usually plateau.

5. Devil's Advocate Sonnet 5 · red-team critique

Both forecasts converge tightly around the Polymarket anchor (4.5-6%) without independently stress-testing the tail — neither models a scenario where PA's growth (52 cases in 2 days cited) combined with new GA/Atlanta daycare cluster and continued Utah spread compounds multiplicatively rather than plateauing, which the brief flags as the key upside risk ("major urban super-spreading event").

Neither forecaster explicitly reconciles the sibling market signal: "Trump-term average ≥5,000" priced at 35% (rising) implies meaningfully higher sustained-transmission expectations than a single-year 10,000 threshold at ~5%, but the brief's stated "roughly consistent" power-law relationship (≥5,000 at ~18%, ≥10,000 at ~6%) isn't tested against this real sibling price of 35% — a notable inconsistency in the illustrative tail-decay assumption neither forecaster interrogates.

Both treat the CDC-reported case count as authoritative without weighing the "PA controversy" (CDC declining to add deaths pending review) — if reporting lags or undercounts are being contested now, year-end revisions/backlogs could push the final tally meaningfully higher than the live Sept 10 snapshot suggests, a scenario neither forecast addresses.

Forecast 1's claim that "year-end reporting lag works against the counter" is asserted without justification — reporting lag could just as easily mean cases occurring in Nov-Dec are confirmed and added *after* Dec 31 but backdated to 2026 in the CDC's system (a common surveillance practice), which would cut against the "No" case; this logic is stated confidently but is not clearly correct either way.

Neither forecaster explicitly incorporates the elimination-status decision (PAHO, expected November 2026) as a potential feedback/salience event — a formal loss-of-elimination announcement could trigger increased public/political attention, testing surges, and case-finding (i.e., ascertainment effects) that mechanically raise the confirmed case count independent of true transmission acceleration.

Both forecasts sit essentially on top of each other (4.5% vs 6%) and anchor almost entirely on Polymarket's 7% rather than triangulating with the base-rate Bayesian estimate (~3-8%) and the extrapolation range (4,000-7,800) to justify a wider or more differentiated confidence interval — this convergence suggests insufficient independent reasoning rather than genuine agreement.

6. Aggregator Fable 5.1 · final calibrated forecast

6% (76% confidence)

Yes: 6% No: 94%

With ~3,294 cases through Sept 10, reaching 10,000 requires ~6,700 more cases in ~16 weeks (~420/week), roughly 4-5x the year-to-date pace and well above even Pennsylvania's peak burst (~180/week), while the era's largest outbreaks (SC, West Texas) plateaued within months and Utah is already flattening. The critique's points on sibling-market inconsistency, reporting revisions, and ascertainment effects are real but modest: none plausibly generates thousands of additional confirmed cases by year-end, and the Trump-term ≥5,000 average market reflects multi-year expectations rather than this single-year 10,000 bar. Long-shot tail markets like Polymarket's 7% tend to be slightly overpriced, so I sit just below the anchor, between the two forecasts, leaving meaningful tail mass for a major urban super-spreading event or large year-end backfill.

Pipeline Timing

Total pipeline time: 158.9s

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