The largest documented person-to-person Andes virus transmission event in history. 34 cases, 11 deaths, traced to a single birthday gathering in Patagonia.
The Epuyén outbreak in Chubut Province, Argentina, between November 2018 and February 2019 remains the most thoroughly documented person-to-person hantavirus transmission event ever recorded. The outbreak began at a birthday gathering on 25 November 2018 attended by approximately 25 people; the index case fell ill several days later and the cluster propagated through three identifiable generations of transmission before being contained.
The outbreak transformed clinical understanding of Andes virus, which had been suspected of person-to-person transmission since the 1990s but never traced through generations of cases with the resolution achieved at Epuyén. The 2020 NEJM analysis remains the reference for hantavirus interpersonal transmission biology.
A single individual exposed to long-tailed pygmy rice rat (the Andes virus reservoir) attended a birthday celebration on 25 November 2018, fell ill, and died.
Among ~25 attendees of the birthday party, multiple cases developed within 2-4 weeks. Several attended the funerary wake of the index case, where additional transmission occurred.
Household members of generation-2 cases who did not attend the birthday party — including healthcare workers without adequate PPE and intimate partners — formed the third transmission ring. Containment was achieved through aggressive contact tracing and isolation by Argentine and Chilean health authorities.