Andes orthohantavirus (ANDV)
Andes orthohantavirus (ANDV) is a hantavirus endemic to the Southern Cone of South America — primarily Argentina and Chile — and is responsible for the most severe form of hantavirus pulmonary syndrome. It is unique among hantaviruses in being able to spread directly from person to person. The 2026 MV Hondius outbreak has been its most internationally significant event.
Virology
ANDV is an enveloped, negative-sense single-stranded RNA virus with a tripartite genome (S, M, L segments) encoding nucleocapsid protein, two glycoproteins (Gn and Gc) and an RNA-dependent RNA polymerase respectively. Multiple genetic lineages have been characterized — Andes-Sur, Andes-Cent, Andes-Norte and others — that correlate with geographic origin. Reverse genetics systems exist but the virus is BSL-3 (BSL-4 in some jurisdictions) which constrains research.
Geographic range and reservoir
The primary reservoir is the long-tailed pygmy rice rat, Oligoryzomys longicaudatus, which ranges from southern Argentina and Chile through Patagonia, with a discontinuous distribution into the Andean valleys further north. Human cases have been reported from at least Argentina, Chile, Brazil (south), Uruguay, Bolivia and Paraguay. Rodent population dynamics — particularly bamboo mast events that produce population booms — are correlated with case clusters.
Person-to-person transmission
ANDV is the only hantavirus with confirmed person-to-person transmission, documented across multiple outbreaks: El Bolsón (1996), Los Antiguos (2003), Bariloche (multiple), and Epuyén (2018-2019). The Epuyén cluster involved at least 34 cases and 11 deaths, with up to 4 sequential generations of transmission. Genomic studies show transmission requires close, sustained contact, and the index case is typically infectious during prodrome and early cardiopulmonary phase. Sexual transmission has been documented. Healthcare-associated transmission is preventable with appropriate PPE.
The MV Hondius cluster (2026)
In March 2026, an outbreak emerged among passengers and crew of the expedition cruise vessel MV Hondius operating in the Drake Passage and South Atlantic. Initial cases were attributed to environmental rodent exposure at a brief Patagonian shore landing, but the rapid emergence of secondary cases among confined shipboard contacts strongly suggested person-to-person spread, later confirmed by genomic sequencing. An evacuation charter flight from St Helena to Johannesburg on 25 April 2026 produced a small downstream cluster among flight crew and passengers. The MV Hondius event is the largest documented ANDV propagation outside Patagonia and triggered a WHO Disease Outbreak News notice.
Surveillance and the future
Several ANDV countermeasures are in development: convalescent plasma protocols, monoclonal antibody candidates (notably JL16 and SAB-159), and DNA vaccines from USAMRIID. None is licensed. Wider availability of rapid molecular diagnostics, expansion of ICU and ECMO capacity in Patagonian referral centers, and rodent population modeling tied to climate variables are active priorities for the region.
- •ANDV is endemic to Argentina and Chile, with a Patagonia core
- •Reservoir: Oligoryzomys longicaudatus (long-tailed pygmy rice rat)
- •The only hantavirus with documented person-to-person transmission
- •Case fatality 35-50%, mitigated by early ECMO
- •MV Hondius (2026) is the largest documented ANDV cluster outside Patagonia
FAQ
How is ANDV different from Sin Nombre virus?+
Sin Nombre causes HPS in North America (deer mouse reservoir) and does not spread person to person. ANDV causes HPS in South America (rice rat reservoir), has a hemorrhagic component, and does spread person to person.
Is there a vaccine for ANDV?+
No licensed vaccine exists. Several DNA vaccine candidates have completed Phase 1 trials. Argentine and Chilean research groups are evaluating monoclonal antibodies for both prevention and treatment.