Idaho Health Advisory: Testing for Hantavirus

HEALTH ALERT NETWORK

Health District 4

Advisory for Healthcare Providers

Idaho Health Advisory: Testing for Hantavirus

May 20, 2026

An outbreak of Andes virus, a type of hantavirus, on the cruise ship M/V Hondius has raised concern about the possibility of Andes virus cases in the United States, including Idaho. CDC and public health departments in several states are monitoring the health of U.S. passengers from the ship and U.S. air travel contacts of passengers who became symptomatic and were subsequently confirmed.

Idaho Risk Assessment

At this time:

• There are no Idahoans under monitoring for Andes virus
• No Idaho residents were passengers on the M/V Hondius or identified as possibly exposed contacts
• The risk to the Idaho public remains very low

The primary hantavirus concern in Idaho remains Sin Nombre virus exposure associated with deer mice or rodent-infested environments such as:

• Cabins
• Sheds
• Campsites
• Homes and outbuildings

Sin Nombre virus is the primary cause of Hantavirus Pulmonary Syndrome (HPS) in North America and Idaho, a rare but potentially severe respiratory disease.

Hantavirus Overview

Hantaviruses are a group of viruses that have co-evolved with specific wild rodent hosts and are typically spread to people from infected rodent hosts. In Idaho, Sin Nombre virus is carried by deer mice and is not spread from person to person. About one Sin Nombre virus infection a year is reported. The risk of infection with Sin Nombre virus is greater in spring and summer when rodent populations increase and people could have more exposure to rodent-infested environments such as cabins, sheds, and campsites.

Andes virus, carried by the long-tailed pygmy rice rat, is endemic in South America and the only hantavirus known to spread from person to person. Several other New World hantaviruses are endemic to the United States; none are transmissible from person to person, but all can cause HPS (see https://www.cdc.gov/hantavirus/hcp/clinical-overview/hps.html). Hantavirus infection in which patients experience non-specific viral symptoms without cardio-pulmonary symptoms can also occur. An Old World hantavirus, Seoul virus, has also been found in the United States, primarily in association with Norway rats. Seoul virus causes hemorrhagic fever with renal syndrome (HFRS) (see https://www.cdc.gov/hantavirus/hcp/clinical-overview/hfrs.html).

Clinical Presentation

Hantavirus infections typically present in two major clinical syndromes: hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS).

• HPS primarily affects the lungs. Following rodent exposure, symptoms generally emerge between 1-8 weeks. Early manifestations include fatigue, fever, and myalgia, with muscle aches often concentrated in large muscle groups, such as the thighs, hips, back, and occasionally the shoulders. Approximately one-half of HPS patients also experience additional symptoms such as headaches, dizziness, chills, and gastrointestinal issues, including nausea, vomiting, diarrhea, and abdominal pain.
• HFRS primarily targets the kidneys. Symptoms typically develop within 1 to 2 weeks of rodent exposure, although in some cases they may appear up to 8 weeks later. The initial presentation is often abrupt and includes intense lower back pain, abdominal pain, fever, chills, nausea, and blurred vision. As the illness progresses, patients may experience hypotension, impaired tissue perfusion, internal bleeding, and acute kidney failure, which can result in severe fluid overload.

Recommendations for Clinicians

Clinicians should consider testing for New World, non-Andes hantavirus (which includes Sin Nombre virus) in patients who have signs and symptoms compatible with HPS or other hantavirus infection AND have a history of known or suspected exposure to sylvatic rodents or rodent excreta (e.g., urine, droppings, or nesting materials). Contact the Idaho Bureau of Laboratories (statelab.idaho.gov) to discuss Sin Nombre virus serologic testing. Sin Nombre virus testing is also available at commercial laboratories.

Clinicians should consider Andes virus infection in patients who have signs and symptoms compatible with hantavirus infection AND either 1) had direct contact with a person associated with the M/V Hondius Andes virus outbreak, OR 2) were exposed to environments in southern South America contaminated with long-tailed pygmy rice rat excreta.

• Contact Central District Health, 208-327-8625, or the Idaho Department of Health and Welfare, Epidemiology Section, 208-334-5939, immediately to report a suspected Andes virus case and for assistance with diagnostic testing for Andes virus.
• Note that assays designed to detect Andes virus specifically may not detect other New World hantaviruses endemic in the United States.

Clinicians should consider infection with Old World hantaviruses in patients who have symptoms consistent with HFRS AND have a history of known or suspected exposure to Norway or roof rats or their excreta in the United States or to wild rodents or their excreta in Europe, Asia, and Africa. Contact Idaho Bureau of Laboratories to facilitate Old World hantavirus testing.

Serologic testing for New World hantavirus may be negative if collected less than 72 hours after symptom onset, in which case a second specimen should be collected more than 72 hours after symptom onset to rule out New World hantavirus infection. Do not use serologic testing to screen for hantavirus in asymptomatic people because antibodies are not present during incubation. Viremia may be low or undetectable by PCR by about 7 to 10 days after symptom onset.

CDC’s Viral Special Pathogens Branch (VSPB) is available to discuss hantavirus diagnostic testing by calling the CDC Emergency Operations Center at 770-488-7100 and requesting VSPB’s on-call epidemiologist. VSPB cannot accept specimens without prior consultation.

Additional Resources

Centers for Disease Control and Prevention

About Hantavirus, https://www.cdc.gov/hantavirus/about/index.html

About Andes virus, https://www.cdc.gov/hantavirus/about/andesvirus.html

Hantavirus disease trainings for healthcare providers, https://www.cdc.gov/hantavirus/hcp/training/index.html

World Health Organization

Hantavirus Disease Outbreak News, https://www.who.int/emergencies/emergency-events/item/2026-e000227

New England Journal of Medicine

Martínez VP, Valeria, Di Paola N, Alonso DO, et al. “Super-Spreaders” and Person-to-Person Transmission of Andes Virus in Argentina. New England Journal of Medicine. 383. 2230-2241.https://doi.org/10.1056/nejmoa2009040