1993 Four Corners outbreak and virus identification
CDC's summary of the first recognized U.S. outbreak explains that a newly recognized hantavirus was identified in June 1993 as the cause of severe respiratory illness (hantavirus pulmonary syndrome, HPS) in the southwestern United States. Through December 31, 1993, CDC reported 53 persons meeting the surveillance case definition; illness onset for many residents of Arizona, Colorado, or New Mexico clustered in April–July 1993. Investigators linked the virus to deer mice and discussed naming tied to geography (initial references included proposed names such as Muerto Canyon virus in MMWR).
The CDC Emerging Infectious Diseases retrospective on the 25th anniversary of the Four Corners outbreak provides additional narrative context on recognition of the syndrome and early investigations (November 2018 article).
U.S. surveillance after 1993
CDC reports that national hantavirus disease surveillance began during the 1993 Four Corners outbreak; HPS became nationally notifiable in 1995. Case reporting later expanded: as of the end of 2023, CDC lists 890 laboratory-confirmed U.S. cases since surveillance began in 1993, including both HPS and non-pulmonary infections captured after reporting rules broadened in 2015.
How understanding evolved
- Clinicians learned to suspect HPS when flu-like illness progresses to cough, shortness of breath, and respiratory failure after rodent exposure—CDC's clinician brief emphasizes early intensive care because deterioration can be rapid.
- Diagnostic approaches consolidated around serology and molecular testing; CDC outlines IgM detection and PCR among acute laboratory criteria for confirmed illness.
- Prevention messaging centered on rodent exclusion and safe cleanup because aerosols from fresh urine, droppings, or nesting material are a primary route described by CDC for North American strains carried by wild rodents.
Sin Nombre, Andes, and geography
CDC's clinician brief notes that different hantaviruses circulate in the United States and that North American strains identified to date have not been observed spreading person-to-person. Andes virus, found in South America, is the strain repeatedly flagged by CDC and WHO as having rare, close-contact-dependent human-to-human transmission.
WHO's January 2019 Disease Outbreak News on Argentina illustrates how Andes virus outbreaks can trigger intense local investigations: it describes dozens of laboratory-confirmed HPS cases in Chubut Province with epidemiologic links and discussion of potential person-to-person transmission under investigation at that time, alongside regional endemic areas described by Argentine authorities.
For maps of overall U.S. case counts by state (not county, to protect privacy), CDC's reported cases page publishes distribution summaries based on national surveillance data through 2023.