Purpose
- The purpose of this document is to support health departments in managing individuals who have experienced a potential exposure associated with the M/V Hondius Andes virus outbreak.
- Andes virus is a type of hantavirus and the only type that is known to spread person-to-person.
Scope
This interim guidance reflects current evidence as of May 14, 2026, and may be updated as new information is available.
What has changed
- Updated definitions
- Updated stratification for people who were on an aircraft with a symptomatic case-patient
- Clarified monitoring and modified activities recommendations for individuals with high-risk exposures
State of science and need for precaution
Our current understanding is that person-to-person transmission of Andes virus is relatively rare and generally associated with prolonged close contact. There is also no documented evidence of presymptomatic transmission. At the same time, the severity of hantavirus pulmonary syndrome and the lack of specific antiviral therapy or a vaccine underscore the importance of preventing secondary transmission in the United States. Even with close monitoring, there is the possibility that early symptoms might not be recognized, and people infected with Andes virus are thought to be most infectious around the time of symptom onset. The goal of the following recommendations is to reduce the likelihood of secondary transmission while monitoring is ongoing, even if the overall risk to the public remains low.
Definitions
For the purposes of this guidance, the following definitions apply.
Confirmed case: Laboratory confirmation of hantavirus by PCR or IgM serology
Suspect case: Illness compatible with hantavirus in an individual who had contact with a confirmed hantavirus case within the previous 42 days and for whom confirmatory test results are not yet available
Non-case: A negative laboratory result for hantavirus by IgM serology on a specimen collected from an acutely symptomatic person ≥72 hours after symptom onset
Compatible illness includes acute (or history of) fever (100.4°F/38°C or above), myalgia, chills, acute gastrointestinal (e.g. nausea, vomiting, diarrhea, abdominal pain) or acute respiratory (e.g. cough, shortness of breath, chest pain, difficulty breathing) symptoms, during a 42-day period after exposure to Andes virus.
Incubation Period
4 to 42 days, with a median of 18 days
Exposure risk stratification
For the purpose of this response, contacts are stratified into two levels.
Contacts with high-risk exposure:
- Being on board the M/V Hondius at any time from April 6 (date of symptom onset for the index case-patient) through the date of disembarkation of the exposed passenger cohort; or
- Answering "yes" to any of the exposure questions in Section 1.2 of the questionnaire (Appendix 1); or
- Being on an aircraft with a symptomatic case-patient and sitting within two seats in any direction*
- If the exact seat number of the case-patient is not known, the zone will be expanded to include the same row as, two rows in front of and two rows behind the case-patient.
*Aircraft crew members and anyone who provided direct assistance to the case-patient on board the aircraft should be individually assessed for high-risk exposures.
Standard monitoring group:
- Being on an aircraft with a symptomatic case-patient and sitting outside of the high-risk zone
Risk-based management for contacts
All contacts
Health departments should provide all individuals identified as contacts with a way to reach the health department at any time (24/7), information on signs and symptoms and general precautions, such as hand hygiene, and instructions on what they should do if they become symptomatic.
The recommended monitoring period is for 42 days after the last potential exposure. For passengers on the M/V Hondius, day 0 of the monitoring period is the date of disembarkation from the ship, provided no further exposures occur. During this period, all contacts should take their temperature at least one time daily and monitor for symptoms of hantavirus. They should be instructed to self-isolate immediately in a designated space away from others (preferably with a private bathroom) if they develop fever or any of the following symptoms, and to call the health department immediately for further instructions.
Symptoms for monitoring:
- Fever, measured ≥ 100.4°F (38°C) or subjectively
- New or worsening
- Headache
- Nausea and/or vomiting
- Diarrhea
- Muscle aches/back pain
- Chest pain
- Cough
- Difficulty breathing/shortness of breath
Health departments should monitor contacts as specified by the risk level below, until 42 days after their last potential exposure. Monitoring activities may include:
- Conducting regular check-ins to assess fever and symptoms and overall health status
- Reviewing temperature logs or other symptom reports submitted by the contact, if requested by the health department
- Reinforcing recommendations on activity modifications and infection prevention measures, and actions to take if symptomatic
- Documenting health department interactions with the contact and following up promptly if a check-in is missed
The goal of monitoring is to support the individual while facilitating early detection, rapid public health response, and coordinated access to clinical care if fever or other symptoms develop. Health departments should contact the CDC Viral Special Pathogens Branch by calling the CDC Emergency Operations Center at 770-488-7100 for clinical consultation and/or to request testing in the event that a contact develops symptoms. If testing is warranted, contacts should remain isolated pending test results.
Contacts with high-risk exposure
Location and housing
In consultation with public health authorities, asymptomatic contacts with high-risk exposure may have the option for home-based management (i.e., monitoring with modified activities), facility-based management at the National Quarantine Unit in Nebraska, or management at a location identified by their health department.
Decisions regarding where these individuals should reside during the monitoring period should be based on access to healthcare, the home environment, comorbidities, capacity to comply with public health directions, and ability to perform essential daily tasks. The individual should have a suitable home environment with access to a designated space in the home to isolate away from others immediately if symptoms develop, ideally with access to a private bathroom, for the duration of the monitoring period. If they typically share a residence with other people, the most protective option is to reside apart (in a separate room with separate bathroom, or at a different location) during their monitoring period.
Health departments should identify a hospital with capacity to isolate patients and to provide critical care, including extracorporeal membrane oxygenation (ECMO); CDC can provide technical assistance as needed.
General precautions
Health departments should advise all individuals with high-risk exposure to modify their activities during the monitoring period to protect their household members and communities as follows:
- Practice good hand hygiene
- Ensure good ventilation
- Wear a respirator or well-fitting mask that covers the mouth and nose, if indoors with others
- Maintain distance
- Avoid kissing, hugging, or other intimate contact
- Avoid sharing a bedroom with anyone
- Avoid exposing others to bodily fluids
- Avoid sharing items that may be contaminated (e.g., toothbrushes, cigarettes/vapes/hookah, or unwashed towels, bedding, or clothing, etc.)
- Avoid sharing food out of the same plate or bowl, eating from the same utensil, or sharing beverages
- Delay nonessential medical or dental appointments
- Coordinate any urgent or necessary care with the health department in advance and notify the healthcare facility
Monitoring
- Monitoring by the health department should occur twice daily, in person
Travel and movement
- Individuals with high-risk exposure should stay home and away from others
- This means, unless it is a life-threatening emergency* or they are instructed by public health authorities:
- They should not enter any buildings, except their residence
- They should not allow other people to enter their residence^
- They may spend time outdoors within walking distance of their residence. They should not come in contact with other people and avoid crowded settings (including outdoors)
- Any essential travel, for example to return individuals to their jurisdiction of residence or to facilitate access to urgent medical care, should be coordinated by authorities
*If it is a life-threatening emergency they should first, call 911 and tell the dispatcher right away that they have been exposed to Andes virus so responders can take proper precautions; then, they should call their health department emergency contact.
^If someone else must enter the home, for example to conduct necessary repairs, they should contact their health department for instructions.
Standard monitoring group
Health departments should regularly monitor individuals in this group. There are no recommended travel restrictions or activity modifications for these individuals. If individuals in the standard monitoring group intend to travel outside the jurisdiction, they should notify the health department of jurisdiction for their current location, and the health department should notify and coordinate with the receiving jurisdiction in advance of travel. If travel is international, CDC can assist with making notifications to destination authorities.
Laboratory diagnostics
CLIA diagnostic assays for detection of New World hantavirus IgM and IgG antibodies are available at CDC, some state public health laboratories, and Quest Diagnostics. If a serum specimen collected within 72 hours of symptom onset tests negative for IgM and IgG antibodies, a second specimen collected more than 72 hours after symptom onset should be submitted to rule out New World hantavirus infection. Detection of New World hantavirus IgM antibodies indicates recent infection, whereas IgG antibodies indicate past infection. Currently, a CLIA-validated Andes virus–specific rRT-PCR assay is available at the Nebraska Public Health Laboratory. However, sensitivity may be reduced for specimens collected later in the course of illness, as viremia may be low or undetectable beyond approximately 7–10 days after symptom onset. Detailed guidance for laboratory testing of contacts will be provided separately.
Infection prevention and control in healthcare settings
In healthcare settings, for patients with known or suspected Andes virus infection, CDC recommends patient placement in an airborne infection isolation room (AIIR) and the use of a gown, gloves, eye protection, and N95 or higher-level respirator when entering the patient's room (see "Andes Virus" in CDC's online Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions). Detailed guidance for risk assessment and management of potential exposures in U.S. healthcare settings will be provided separately.