PATHOGEN CLASSIFICATION FRAMEWORK

WORKING DOCUMENT

PCF/1.0
ISSUED: 12 MAY 2026
STATUS: DRAFT — OPEN

Pathogen Classification Framework

Transmission-Primary Designation System — Version 1.0

Preamble

A pathogen's most operationally significant characteristic is how it moves. Severity, mortality, and reservoir origin are consequential — but they are downstream of transmission. Containment strategy, public response, resource deployment, and the ceiling on outbreak scale are all determined first by the question: how does this cross?

This framework assigns a single primary classification to any pathogen based on its dominant transmission mechanism. Where a pathogen's mechanism is unknown, contested, or violates established parameters for its class, a distinct designation is assigned rather than forcing a fit. Classifications are not permanent — they track the pathogen's behavior and are revised as understanding develops.

Class Definitions

HERMES

Messenger of the gods — crosses all boundaries, moves faster than response, cannot be stopped at the threshold

Airborne or droplet transmission with sustained human-to-human spread. The pathogen moves faster than containment infrastructure can respond. Behavioral intervention alone cannot hold it. Requires population-level immunity or pharmaceutical intervention to alter trajectory. The defining characteristic is that the vector is air itself — the boundary cannot be sealed.

R₀ TYPICALLY >2 IN NAIVE POPULATION
TRANSMISSION PRECEDES SYMPTOM ONSET
CONTAINMENT REQUIRES NON-PHARMACEUTICAL INTERVENTIONS AT SCALE
FOMITE CONTRIBUTION SECONDARY OR ABSENT

EXAMPLES: SARS-CoV-2 (endemic phase), Influenza (pandemic strains), Measles, Tuberculosis, SARS-CoV-1

CHARON

Ferryman of the dead — nothing crosses without the carrier; control the ferry, control the crossing

Vector-borne transmission requiring a biological intermediary — arthropod, insect, or animal — to complete the crossing. Human-to-human spread is absent or negligible without the vector. The strategic implication is precise: eliminate or suppress the carrier and transmission stops. Containment is tractable but geographically and ecologically constrained.

OBLIGATE BIOLOGICAL VECTOR REQUIRED
DIRECT H2H TRANSMISSION ABSENT OR NEGLIGIBLE
GEOGRAPHIC RANGE DETERMINED BY VECTOR HABITAT
SEASONAL PATTERN TRACKS VECTOR LIFECYCLE

EXAMPLES: Malaria (Anopheles), Dengue (Aedes), Lyme disease (Ixodes), West Nile Virus, Yellow Fever

EROS

Requires proximity — cannot act at a distance; the crossing demands contact

Direct contact transmission — sexual, bloodborne, or sustained physical proximity. The pathogen cannot cross space; it requires the closing of distance. This makes behavior the primary containment lever. Outbreak scale is bounded by contact network density. Characterized by identifiable chains with reconstructible links — epidemiology has traction.

TRANSMISSION REQUIRES DIRECT PHYSICAL CONTACT OR FLUID EXCHANGE
AIRBORNE SPREAD ABSENT
CONTACT NETWORK ANALYSIS IS PRIMARY EPIDEMIOLOGICAL TOOL
BEHAVIORAL INTERVENTION IS SUFFICIENT CONTAINMENT MECHANISM

EXAMPLES: HIV, Hepatitis B/C, Ebola (standard transmission), Syphilis, Mpox (2022 outbreak)

HECATE

Goddess of the threshold — exists at the boundary between worlds; the crossing point is the danger

Zoonotic spillover — the pathogen lives in an animal reservoir and crosses into the human population at points of contact. Human-to-human transmission is limited or absent; the threat is recurrent spillover events rather than sustained chains. The reservoir is the engine. Containment focuses on the interface between species — hunting, wet markets, habitat encroachment, agricultural practice.

PRIMARY RESERVOIR IS NON-HUMAN
HUMAN INFECTION IS SPILLOVER EVENT, NOT ENDEMIC CHAIN
H2H TRANSMISSION LIMITED TO NEGLIGIBLE
OUTBREAK RISK TRACKS HUMAN-ANIMAL INTERFACE CONDITIONS

EXAMPLES: Rabies, Hantavirus (standard rodent-to-human), H5N1 (current), Nipah, MERS-CoV

SPHINX

Poses the question the system cannot yet answer — kills those who cannot solve it

Transmission mechanism unknown, contested, or empirically violating established parameters for the pathogen's expected class. This is not a residual category — it is an active designation indicating that current epidemiological doctrine is insufficient to explain observed transmission. SPHINX demands urgent investigation. Applying a prior classification to a SPHINX-designated pathogen is a systemic failure mode.

OBSERVED TRANSMISSION EVENTS UNEXPLAINED BY KNOWN MECHANISM
OR: PATHOGEN BEHAVIOR VIOLATES PARAMETERS OF ITS PRIOR CLASS
OR: INSUFFICIENT DATA TO ASSIGN PRIMARY CLASS WITH CONFIDENCE
RESOLUTION REQUIRES ACTIVE INVESTIGATION — NOT ASSUMPTION

EXAMPLES: Andes Virus / MV Hondius 2026 (P2P parameters unresolved), SARS-CoV-2 (early phase), COVID-19 fomite/airborne debate 2020

State Transitions

Classifications track behavior, not identity. A pathogen may transition between classes as its transmission dynamics are better understood or as the pathogen itself evolves. The transition must be driven by empirical evidence, not modeling assumptions. Downgrading from SPHINX requires documented resolution of the contested mechanism — not passage of time. SARS-CoV-2: SPHINX (Jan 2020) → HERMES (Mar 2020) → HERMES/endemic (2022–present)
ANDV/HONDIUS: HECATE (pre-2018 doctrine) → SPHINX (Epuyen 2018, confirmed P2P) → SPHINX (Hondius 2026, mechanism still unresolved)
H5N1: HECATE (1997–present) → SPHINX (if sustained H2H confirmed)

Designation Syntax

Historical Index

Pathogen / Event	Designation	Basis	Status
SARS-CoV-2 / COVID-19	HERMES	Sustained airborne H2H, pre-symptomatic transmission, R₀ 2–4+ (ancestral)	Endemic — monitoring
SARS-CoV-2 / COVID-19 (Jan 2020)	SPHINX → HERMES	Initial mechanism contested; fomite vs. airborne debate delayed response	Reclassified Mar 2020
Influenza A H1N1 / 2009	HERMES	Respiratory droplet/airborne, rapid pandemic spread	Resolved — seasonal
Ebola / 2014 West Africa	EROS	Direct contact/fluid transmission; no airborne component confirmed	Resolved
Mpox / 2022 global	EROS	Close contact/skin-to-skin; sexual network amplification	Monitoring
Malaria (P. falciparum)	CHARON	Obligate Anopheles vector; no H2H	Endemic — active
Dengue	CHARON	Aedes aegypti vector; no H2H	Endemic — expanding range
Hantavirus / standard (pre-2018)	HECATE	Rodent reservoir to human spillover; no documented H2H	Reclassified
Andes Virus / Epuyen 2018	SPHINX	P2P transmission documented at brief proximity (4ft, 90min); prior HECATE classification violated	Unresolved
Andes Virus / MV Hondius 2026	SPHINX	P2P parameters unresolved; transmission window, minimum exposure duration, and ship's doctor infection unexplained by current doctrine	ACTIVE
H5N1 / current	HECATE → SPHINX (watch)	Zoonotic to date; sustained H2H not confirmed but proximity events increasing	Elevated monitoring
MERS-CoV	HECATE	Dromedary camel reservoir; limited H2H in healthcare settings	Endemic — monitoring
HIV	EROS	Bloodborne/sexual; no airborne component	Endemic — controlled
Measles	HERMES	Airborne, R₀ 12–18, highest of any known pathogen	Controlled (vaccine) — resurgent in gaps
Tuberculosis	HERMES	Airborne droplet nuclei; prolonged exposure amplifies risk	Endemic — global burden

SPHINX CLASS: ANDV — MV HONDIUS 2026

Andes orthohantavirus. 9 confirmed, 2 suspected, 3 deceased as of 12 May 2026. CFR ~38% symptomatic. Prior doctrine: HECATE (rodent-to-human spillover, no H2H). Epuyen 2018 established P2P transmission at parameters inconsistent with sustained contact requirement. Hondius 2026 confirms: ship's doctor infected in clinical setting; 30+ passengers dispersed across 23 countries before containment; incubation window 4–42 days. SPHINX designation maintained until minimum exposure duration and transmission window are empirically resolved.

Surveillance bias note: prior "prolonged contact" doctrine derived from household chains in rural Andean communities — a product of who gets detected, not a biological constraint.