Case Classification

Confirmed vs Probable

Confirmed and probable cases describe different levels of laboratory and epidemiological evidence under U.S. surveillance case definitions developed by CDC and the Council of State and Territorial Epidemiologists (CSTE). They are not interchangeable, and a case's classification can change over time as additional testing returns.

Key facts

U.S. case definition: CDC / CSTE
Confirmed evidence: Lab (PCR · IgM · IHC · titers)
Probable evidence: Clinical + epi link
Suspect evidence: Clinical, testing pending
Reporting system: NNDSS

Working definitions

The definitions below align with the CDC/CSTE national surveillance case definition for hantavirus pulmonary syndrome.

Confirmed — clinically compatible illness with laboratory confirmation (PCR, IgM-positive serology, IHC of tissue, or rising IgG titers).
Probable — clinically compatible illness with an epidemiologic link to a confirmed case but no confirmatory laboratory result.
Suspect (inconclusive) — clinically compatible illness under investigation; testing pending or non-confirmatory.
Surveillance — a monitoring posture or baseline-context entry, not an individual case.

How classifications can change

Classifications are not fixed at first reporting. A probable case becomes confirmed when paired sera return seroconversion or PCR comes back positive. A suspect case can be reclassified to confirmed or ruled out. HantaScan reflects classification as published in the underlying source and tries to make changes visible rather than overwriting prior context.

CDC vs WHO framing

CDC uses the CDC/CSTE surveillance case definitions for U.S. notifiable-disease reporting through NNDSS. WHO Disease Outbreak News reports adopt event-appropriate categories for international clusters. The categories overlap conceptually but are not identical row-for-row across systems, which matters when reading a multi-country event.

Why HantaScan keeps them separate

Combining classifications produces a cleaner-looking count but loses the underlying evidence level. Keeping confirmed, probable, and suspect rows separate is the standard CDC and CSTE framing, and it is the framing HantaScan adopts.

Implications for citing counts

When citing a hantavirus count, citing 'confirmed' is conservative and defensible; citing a combined total can be useful for tracking an evolving event but should always be paired with the breakdown. A combined number with no breakdown is a red flag, not a finding.

CASE INDEX

Hantavirus surveillance timeline

Date	Location	Status	Cases	Deaths	Source	Signal
2026-05-13	MV Hondius — multi-country South America itinerary International	confirmed	8	3	WHO	WHO Disease Outbreak News third update on the MV Hondius hantavirus cluster: 11 linked records total — 8 laboratory-confirmed, 2 probable, and 1 inconclusive U.S. repatriated traveler. Andes virus identified as the agent of concern. Investigation continues across multiple Member States.
2026-05-08	MV Hondius cluster — WHO update International	surveillance	0	0	WHO	Second WHO Disease Outbreak News update on the MV Hondius cluster raised the confirmed count and described enhanced surveillance for returning passengers across home jurisdictions.
2026-05-05	United States — CDC monitoring posture United States	surveillance	0	0	CDC	CDC announced enhanced case-finding for returning MV Hondius passengers and issued clinician-awareness guidance through HAN. No confirmed U.S. Andes-virus cases linked to the cruise to date; the single U.S. record remains inconclusive.
2026-05-04	MV Hondius cluster — initial WHO report International	surveillance	0	0	WHO	Initial WHO Disease Outbreak News report on a hantavirus cluster linked to the MV Hondius cruise itinerary following Member State notification on May 2. Two confirmed cases and five suspected cases described at first publication.
2025-03-15	United States United States	surveillance	0	0	CDC	CDC and state health departments expanded clinician-awareness messaging on hantavirus pulmonary syndrome following a high-profile case in the rural Southwest that drew renewed national attention.
2023-12-31	United States — cumulative reported total United States	surveillance	864	311	CDC	CDC's Reported Cases of Hantavirus Disease page lists 864 laboratory-confirmed cases of hantavirus pulmonary syndrome in the United States through 2023, with historical case-fatality near 36 percent.
2012-08-16	Yosemite National Park — Curry Village United States	confirmed	10	3	CDC	Ten confirmed HPS cases were tied to the Signature double-walled tent cabins at Curry Village between June and August 2012. Deer-mouse infestation was identified between the cabin walls; the cabins were dismantled and roughly 22,000 visitors were notified.
1995-07-26	United States United States	surveillance	0	0	NNDSS	Hantavirus pulmonary syndrome added to the U.S. list of nationally notifiable diseases, formalizing weekly state-to-CDC case reporting through the National Notifiable Diseases Surveillance System.
1993-11-30	CDC — Atlanta, GA United States	surveillance	0	0	CDC	Sin Nombre virus identified as the etiologic agent of the Four Corners outbreak. The deer mouse (Peromyscus maniculatus) confirmed as the primary U.S. reservoir.
1993-05-14	Four Corners region (AZ · CO · NM · UT) United States	confirmed	17	13	CDC	Cluster of unexplained adult respiratory deaths in the Four Corners region — primarily on the Navajo Nation — prompted the CDC investigation that led to recognition of hantavirus pulmonary syndrome as a new clinical syndrome.

Related on HantaScan

Testing NNDSS Weekly Tables U.S. Monitoring Compare

Primary Sources

CDC Hantavirus CDC Prevention CDC Clinical Overview