Oligoryzomys longicaudatus presence in Tierra del Fuego is formally documented in Parque Nacional Tierra del Fuego by Argentina’s official mammal categorisation authority (SAREM), notwithstanding statements by provincial health officials during the 2026 MV Hondius cruise outbreak investigation that the subspecies does not inhabit the region. A well-documented example occurred in 2019 in the Villa La Angostura and Villa Traful area of Neuquén, when mass Chusquea flowering in Nahuel Huapi National Park triggered a major rodent population explosion, captures doubled, and O. longicaudatus became the most abundant species in the area.  In the 2025–2026 season, experts link the broader rise in Argentine hantavirus cases to climate change accelerating rodent range expansion: rising temperatures allow reservoir rodents to reproduce in new areas, while drought episodes force them out of their habitats in search of food and water, increasing human contact. Bariloche registered its first human hantavirus case of 2026 in May, highlighting the ongoing risk in northern Patagonia.

Notably, in February 2026, while the MV Hondius was still operating out of Chubut, a household cluster of hantavirus was confirmed in Cerro Centinela, Chubut, where three family members were infected and died. Genetic sequencing showed 99.99% similarity between the three cases. The sequential onset of symptoms among household members was considered consistent with person-to-person transmission, although a common rodent source could not be fully excluded.