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 10, 2026, and may be updated as new information is available.
Definitions
For the purposes of this guidance, the following definitions apply.
Confirmed case: Laboratory confirmation of hantavirus by PCR or IgM serology
Probable case: Fatal illness compatible with hantavirus in an individual who had contact with a suspect, probable, or confirmed hantavirus case within the previous 42 days without test results
Suspect case: Illness compatible with hantavirus in an individual who had contact with a suspect, probable, or confirmed hantavirus case within the previous 42 days
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.
Contact
An individual who has had an exposure as described below.
Exposure
Any of the following:
(1) being aboard the M/V Hondius at any time from April 6 (date of symptom onset for the index case) through the date of disembarkation of the exposed passenger cohort;
(2) being within approximately 6 feet of a symptomatic case-patient in an enclosed space for a cumulative duration of ≥15 minutes;*
(3) having direct physical contact with a symptomatic case-patient; or
(4) having contact with respiratory secretions or other bodily fluids from a symptomatic case-patient.
*These thresholds are not absolute and should be interpreted based on the nature and setting of the contact.
Incubation Period
4 to 42 days with a median of 18 days
Exposure risk stratification
Risk for known contacts is stratified into two levels.
High-risk contact:
- Being aboard the M/V Hondius at any time from April 6 (date of symptom onset for the index case) through the date of disembarkation of the exposed passenger cohort is considered high risk due to likelihood of prolonged close contact among passengers and crew, shared living spaces, and the potential for recall bias when assessing exposures and symptom onset; 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*
*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.
Low-risk contact:
Any contact not meeting high-risk criteria who meets at least one of the following:
- Answering “no” to all 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 further away than two seats in any direction
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), education and a fact sheet on Andes virus, including information on signs and symptoms and general precautions such as hand hygiene. They should additionally provide instructions on what contacts should do if they become symptomatic, including how to reach the health department 24/7 and where to seek health care.
The recommended monitoring period is for 42 days after the last potential exposure. During this period, all contacts should take their temperature at least one time daily and monitor themselves for symptoms of hantavirus and also be monitored regularly by public health authorities, as specified by risk level below. 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 other symptoms, and to call the health department immediately for further instructions.
- 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
Monitoring by the health department may include:
- Conducting regular check-ins to assess fever and symptoms and overall health status
- Monitoring can be conducted by phone, video conferencing, other electronic means (e.g., text message, email, app, web form), or in person, according to resources available in that jurisdiction.
- Reviewing temperature logs or other symptom reports submitted by the contact (if requested by 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 daily monitoring is to support the individual while facilitating early detection and rapid public health response if fever or other symptoms develop. Health departments should contact CDC Viral Special Pathogens Branch by calling the CDC Emergency Operations Center at 770-488-7100 for clinical consultation and/or to request testing. If testing is warranted, contacts should remain isolated pending test results.
High-risk contacts
Location and housing
High-risk contacts have the option for home-based management (i.e., monitoring with modified activities) or facility-based management at the National Quarantine Unit in Nebraska or a location identified by a health department of jurisdiction.
If home-based management is preferred, the health department should coordinate with the high-risk contact to assess their capacity to follow public health directions. 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. 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.
Monitoring
Health departments should monitor high-risk contacts daily until 42 days after the last known high-risk 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.
Travel
Health departments should advise high-risk contacts not to travel (domestically or internationally) during the monitoring period. However, if they do intend to travel, travel should be by chartered flight (no commercial air travel) and/or personal vehicle only. Additionally, high-risk contacts should notify the health department of jurisdiction, 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.
Activities
Health departments should advise high-risk contacts to modify their activities during the monitoring period to protect their household members and communities. See the following table for more information.
Recommended activity modifications for high-risk contacts:
- Limiting activities outside the home to those that are essential. For example:
- Delay nonessential medical or dental appointments
- Coordinate any urgent or necessary care with the health department in advance and notify the healthcare facility before arrival
- Minimizing close or prolonged interactions with others
- If it is necessary to be around others in indoor spaces (e.g., household members or others outside the home):
- Practicing good hand hygiene
- Wearing a well-fitting respirator or mask that covers the mouth and nose
- Maintaining distance when possible
- Ensuring good ventilation
Activities that are not recommended for high-risk contacts:
- Sharing a bed with someone else (in case fever or symptoms develop while asleep)
- Sharing personal items, including towels, bed linens, clothing, toothbrushes, utensils, cigarettes/vapes, etc.
- Sharing food out of the same plate or bowl, sharing beverages
- Attending social events
- Visiting crowded venues, including movie theaters, concert halls, or professional sports events
Low-risk contacts
Health departments should regularly monitor low-risk contacts and advise them to self-monitor for fever and symptoms daily for 42 days after the last known exposure; there are no recommended travel restrictions or activity modifications other than general precautions such as hand hygiene.
If low-risk contacts intend to travel outside the jurisdiction, they should notify the health department of jurisdiction, 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. A CLIA Andes virus–specific rRT-PCR assay is not currently available in the United States; once available, it could be used to test symptomatic patients. 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 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.