Pandemic Watch
Andes virus vs Hantaan virus
A factual side-by-side comparison of two hantavirus strains: Andes virus and Hantaan virus. Reservoir biology, geographic distribution, clinical course, case-fatality rate, and outbreak history.
Discovery and history
Andes virus
Andes virus was isolated in 1995 from cases in El Bolsón, in the Argentine province of Río Negro, and was named for the mountain range running through its endemic region. The following year, an outbreak in the same town produced evidence that fundamentally changed hantavirus epidemiology: case clusters in family members and physicians who had attended the index patients in Buenos Aires showed transmission patterns that could not be explained by shared rodent exposure. Genetic sequencing of the patient isolates confirmed direct human-to-human spread — the first such evidence for any hantavirus. Subsequent outbreaks have repeatedly reproduced the finding.
Hantaan virus
Between 1951 and 1954, roughly 3,000 United Nations soldiers near the Hantaan River in central Korea developed an unexplained hemorrhagic fever with renal involvement. The case-fatality rate approached 10 percent. The disease was given the descriptive name 'Korean hemorrhagic fever' and an etiology was sought for the next 25 years. Karl Johnson and Ho Wang Lee finally isolated the causative agent from striped field mice in 1976, naming it after the river. The discovery established hantaviruses as a coherent family and provided the type species against which all subsequent strains have been characterized.
Reservoir and ecology
Andes virus
The primary reservoir is the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), a small nocturnal rodent native to the Patagonian forests and steppes of Argentina and Chile. Like other hantavirus reservoirs, infected animals are persistently and asymptomatically infected and shed virus throughout life. The rodent prefers brushy forest edges and the bunchgrass habitats of southern South America, putting it in contact with rural and peri-urban human settlements where its populations periodically expand following bamboo (caña colihue) seeding events that release abundant food.
Hantaan virus
The reservoir is the striped field mouse (Apodemus agrarius), widely distributed across temperate East Asia in grasslands, agricultural fields, and forest margins. The species is intimately associated with grain agriculture across China, Korea, and the Russian Far East, which puts it in regular contact with farmers, harvesters, and rural residents. Seasonal peaks in HFRS cases track the autumn harvest and the spring planting cycles when human exposure to rodent-contaminated environments is highest.
Clinical course
Andes virus
The clinical course mirrors Sin Nombre virus infection: a one-to-eight-week incubation, then a febrile prodrome with severe myalgia, then a cardiopulmonary phase with pulmonary edema and shock. Case-fatality is similar at 35 to 40 percent. The crucial epidemiological difference is the documented person-to-person transmission — close family contacts, healthcare workers, and acquaintances can be infected through respiratory droplets and possibly fomites during the symptomatic phase of an index case. Documented incubation periods for human-acquired cases extend to about 45 days, the period over which exposed contacts are monitored.
Hantaan virus
HFRS classically progresses through five phases: febrile (fever, myalgia, headache, lasting 3-7 days), hypotensive (sudden drop in blood pressure, lasting hours to days), oliguric (acute kidney injury with reduced urine output, lasting 3-7 days — most deaths occur here), diuretic (recovery of urine output), and convalescent (gradual recovery over weeks to months). Hemorrhagic manifestations — petechial rash, conjunctival hemorrhage, gastrointestinal bleeding — give the syndrome its name. The case-fatality rate of 5 to 15 percent is lower than for HPS but the overall morbidity is substantial.
Notable outbreaks
Andes virus
The 1996 El Bolsón outbreak (Argentina) provided the original evidence of person-to-person transmission. The 2018 to 2019 Epuyén outbreak in Chubut province produced 29 cases and 11 deaths across at least three generations of transmission and prompted provincial-level quarantine measures unprecedented for a hantavirus event. The 2025 to 2026 multi-country cluster among passengers and crew of an expedition cruise — currently tracked on this site — appears to involve Andes virus contracted in Tierra del Fuego.
Hantaan virus
The Korean War cases between 1951 and 1954 remain the largest documented Hantaan virus event. Modern outbreaks are smaller — clusters in agricultural workers, military trainees, or rural communities during harvest peaks. China has documented major HFRS outbreaks tied to flood-displacement of rodent populations.
Prevention
Andes virus
In addition to standard rodent-exposure precautions, Andes virus is the one hantavirus where person-to-person transmission protocols matter. Public health response in Argentina and Chile includes respiratory isolation of symptomatic cases, contact tracing for close contacts during the symptomatic period, and 45-day monitoring of contacts for incubation-period symptoms. Travelers to endemic regions during periods of known outbreak should follow local public health guidance.
Hantaan virus
Inactivated HFRS vaccines have been licensed in South Korea since 1990 and in China shortly thereafter. They are recommended for high-risk occupational groups (military, agricultural workers, lab researchers) and provide partial protection against Hantaan and Seoul viruses. Uptake outside occupational programs is limited. Beyond vaccination, standard rodent-exposure precautions and grain-storage rodent-proofing reduce risk.
Full strain profiles: Andes virus · Hantaan virus. For the broader disease guide, see hantavirus.
