Hantavirus Outbreaks: History & Current Surveillance

Korean War Hemorrhagic Fever

Roughly 3,000 United Nations soldiers develop a mysterious hemorrhagic fever with renal syndrome during the Korean War (Jonsson, Figueiredo & Vapalahti, Clin Microbiol Rev 2010). Symptoms include fever, hemorrhage, and kidney failure. The cause is unknown at the time and is later identified as Hantaan virus. The outbreak spurs decades of military-funded infectious disease research — including the U.S. Army's HFRS vaccine programme that is still running trials today (see treatment).

Hantaan Virus Isolated — Ho Wang Lee

Korean virologist Ho Wang Lee isolates the causative agent from striped field mice near the Hantaan River in Korea, naming the virus (and the entire family) after the river. This discovery provides the first definitive cause for Korean hemorrhagic fever and opens the field of hantavirus research globally.

Four Corners Outbreak — Sin Nombre Virus Discovered

A cluster of previously healthy young adults in the Four Corners region (New Mexico, Arizona, Colorado, Utah) die rapidly from an unknown respiratory illness. CDC investigators identify a new hantavirus — Sin Nombre ("nameless") virus — carried by the deer mouse (Peromyscus maniculatus). Surveillance identifies 24 compatible cases with onset since December 1992, half of them fatal (CDC's surveillance summary, MacNeil et al., Emerg Infect Dis 2011); the first published clinical series of 17 confirmed patients recorded 13 deaths, a 76% case-fatality rate (Duchin et al., N Engl J Med 1994). CDC's case file records 48 cases and 27 deaths (56%) with onset in 1993 — still the largest single year. The discovery creates the disease category of hantavirus pulmonary syndrome.

Black Creek Canal Virus — Florida

A novel hantavirus, Black Creek Canal virus, is identified in Florida, carried by cotton rats. This discovery expands the geographic range of U.S. hantavirus beyond the West, establishing that multiple rodent species and virus strains co-exist across North America.

Andes Virus Cluster — Argentina: First Person-to-Person Transmission

A cluster of cases in El Bolsón, Argentina, provides the first molecular evidence of person-to-person transmission of any hantavirus: sequences from the linked patients were near-identical, including in people with no rodent exposure (Padula et al., Virology 1998). The strain, later named Epilink/96, is the genetic reference point against which the 2018–19 Epuyén outbreak strain was compared. Andes virus remains the only hantavirus with documented human-to-human spread (CDC, WHO).

Seoul Virus in Pet Rats — Global

Multiple outbreaks of Seoul virus — an HFRS-causing hantavirus normally carried by common rats — are identified in domestic pet rat colonies across the United States, Europe, and other regions. This is the first hantavirus associated with domestically kept animals (not wild rodents), though cases remain rare and the illness is generally milder than HPS or severe HFRS strains. Seoul virus is the only HFRS-causing hantavirus found in the United States (CDC clinician brief, May 2024).

Yosemite National Park Outbreak

Ten hantavirus infections among overnight visitors from three states; eight develop HPS, five need intensive care with ventilation, and three die. Nine of the ten had stayed in "Signature Tent Cabins" — double-walled canvas structures whose foam insulation held rodent nests and tunnels. Trapping around the cabins caught a deer mouse in 51% of trap-nights and 10 of 73 deer mice (14%) carried antibodies to Sin Nombre virus (Núñez et al., Emerg Infect Dis 2014). The Park Service notified everyone who had stayed in the cabins between 10 June and 24 August 2012 (WHO Disease Outbreak News, 12 September 2012); the cabins were closed and dismantled.

Seoul Virus Outbreak — U.S. Pet Rat Breeders

A Wisconsin home rat-breeder is hospitalised in December 2016 with fever, low white cells and kidney involvement; a family member falls ill four weeks later. The investigation that follows finds Seoul virus in 31 facilities in 11 states, six of which had exchanged rats with Canadian ratteries. Of 183 people tested in the two countries, 24 (13.1%) had Seoul virus antibodies; three were hospitalised and none died (Kerins et al., CDC's MMWR, February 2018). It is the first known transmission of Seoul virus from pet rats to people in the United States and Canada.

Epuyén, Argentina — The Largest Person-to-Person Hantavirus Outbreak on Record

From November 2018 to February 2019, Andes virus spreads through the town of Epuyén in Chubut Province: 34 confirmed infections and 11 deaths after a single introduction from a rodent. Genome sequencing and contact tracing show that three symptomatic people who attended crowded social events drove most of the spread. The median reproductive number was 2.12 before control measures and 0.96 after isolation of cases and self-quarantine of contacts were enforced once 18 cases had been confirmed. Patients with high viral loads and liver injury were the ones most likely to infect others; disease severity, age and time in hospital were not (Martínez et al., N Engl J Med 2020). WHO cited this outbreak as the precedent when assessing the 2026 cruise-ship cluster.

MV Hondius Cruise Ship Outbreak — First Shipboard Hantavirus Cluster

On 2 May 2026 the United Kingdom notifies WHO of severe respiratory illness aboard the Netherlands-flagged expedition ship MV Hondius, which had left Ushuaia, Argentina, on 1 April with 88 passengers and 59 crew of 23 nationalities and called at Antarctica, South Georgia, Tristan da Cunha, Saint Helena and Ascension. The first patient fell ill on 6 April and died on board on 11 April; the second, a close contact, died in Johannesburg on 26 April and was confirmed by PCR on 4 May. WHO's final tally (Disease Outbreak News, 2 July 2026): 13 cases — 12 laboratory-confirmed and one probable — and 3 deaths (case-fatality ratio 23%), all among people who had travelled on the ship; nine men and four women, median age 65; the three who died were 69, 70 and 79. One U.S. traveller's inconclusive result was later ruled negative and removed from the count on 15 May.

WHO's working conclusion is that the first case was infected on land before boarding (exposure in Chile was ruled out by the incubation window; the exact source is undetermined) and that transmission then occurred person-to-person aboard the ship — near-identical viral sequences from different patients support this. Contact follow-up in 33 countries and territories (317 high-risk contacts quarantined, 336 low-risk self-monitored, all for 42 days) found no secondary case off the ship, and WHO declared the outbreak over on 2 July 2026. Our calculation: 13 of 147 aboard is an attack rate of 8.8% — or 12 of 146 (8.2%) if the first case is treated as the imported one. WHO's own reading: "the virus did not exhibit transmission dynamics consistent with highly transmissible airborne pathogens (such as measles)." A 21-country prospective study of the exposed passengers and crew is under way; its results were not published as of September 15, 2026.