25% — Above 15 human H5N1 cases in the United States during 2026
Kalshi 25% · 8 contracts · $0 volume · medium confidence
Updated 2026-05-28 20:44:05 UTC

Why this matters:
This contract resolves to 'yes' if 15 or more confirmed human H5N1 cases are reported in the United States during 2026. The 15% probability reflects that such an outbreak would represent a significant escalation from recent years. H5N1 cases in the U.S. have been sporadic, with most occurrences limited to agricultural workers with direct animal exposure. The probability depends primarily on two factors: whether the virus continues spreading in U.S. livestock populations (particularly dairy cattle) and whether human-to-animal transmission rates increase or human-to-human transmission emerges. As of mid-2026, actual case data through the year will provide the primary signals for resolution. The contract's value chain shows declining probabilities at higher thresholds—above 10 cases trades at 6% and above 15 at 3%—suggesting market participants view sustained human transmission as unlikely but not impossible. Seasonal patterns and ongoing surveillance will shape how certainty evolves through the remainder of 2026.

Key factors:
- Current confirmed U.S. H5N1 cases in humans through May 2026 compared to historical annual totals (typically 0-3 cases annually before 2024)
- Extent of H5N1 circulation in U.S. livestock, particularly dairy herds, as a prerequisite for human exposures
- Evidence of human-to-human transmission capability, as nearly all historical U.S. cases involved direct animal contact
- Laboratory testing and reporting capacity across states to detect and confirm cases
- Seasonal transmission patterns, particularly during fall/winter months when influenza activity typically increases

Contracts:
- Above 2 human H5N1 cases in the United States during 2026: Above 2 — 33¢ Kalshi $0 (weight 13%)
- Above 0 human H5N1 cases in the United States during 2026: Above 0 — 44¢ Kalshi $0 (weight 13%)
- Above 1 human H5N1 cases in the United States during 2026: Above 1 — 38¢ Kalshi $0 (weight 13%)
- Above 10 human H5N1 cases in the United States during 2026: Above 10 — 10¢ Kalshi $0 (weight 13%)
- Above 15 human H5N1 cases in the United States during 2026: Above 15 — 8¢ Kalshi $0 (weight 13%)
- Above 3 human H5N1 cases in the United States during 2026: Above 3 — 27¢ Kalshi $0 (weight 13%)
- Above 5 human H5N1 cases in the United States during 2026: Above 5 — 22¢ Kalshi $0 (weight 13%)
- Above 7 human H5N1 cases in the United States during 2026: Above 7 — 16¢ Kalshi $0 (weight 13%)

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## Methodology

SimpleFunctions aggregates live YES-side prices from Kalshi and Polymarket contracts bound to this question. For binary topics the headline is the liquidity-weighted mid-price (weight = log(1 + 24h volume) × freshness, where freshness is 1.0 if updated <24h, 0.7 if <7d, 0.4 otherwise). For multi-outcome (winner-take-all) topics the headline is the current leader's price — disjoint outcomes are never arithmetically averaged. Snapshots refresh every 5 minutes during market hours.

## SF Signal

- SF Index, regime, and 30d Brier calibration are computed separately and surfaced at https://simplefunctions.dev/admin/calibration.
- No SimpleFunctions index / regime / calibration signal is bound to this topic yet — the headline above is market-derived only.

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*Last verified: 2026-05-28T20:20:07.631Z*

By SimpleFunctions — https://simplefunctions.dev/

Cite as: "25% per prediction markets (SimpleFunctions, May 2026)"
Canonical: https://simplefunctions.dev/answer/h5n1count
Full data: https://simplefunctions.dev/api/public/query?q=Above%2015%20human%20H5N1%20cases%20in%20the%20United%20States%20during%202026
Provider: SimpleFunctions — https://simplefunctions.dev