This is a longitudinal observational cohort study enrolling individuals with a defined exposure to Andes Virus (ANDV) who are confined or quarantined. Subjects can be included in one of the three tiers and are all followed from one tier to the other and/or to end of quarantine: (a) Tier 1 (Exposure/Enrolment): from X0/E0 to P0 (first RT-qPCR positive); (b) Tier 2 (Pre-symptomatic infection): from P0 to S0 (first symptom onset); (c) Tier 3 (Symptomatic disease): from S0 to clinical outcome (clinical resolution or death). Epidemiological information from their exposure (X0) is also collected. The overarching goal is to delineate the natural history and the virologic and immunologic mechanisms and consequences of infection with sampling intensity matched to biological inflection points, i.e., higher frequency around P0 and symptom onset (S0) and lower intensity elsewhere. Clinical care is not directed by the protocol. All medical decisions remain under treating clinicians. This protocol remains observational and purposely low-intensity because it does not direct clinical care, and uses a trigger-based, phase-adaptive tier structure (X0/E0, P0, S0) that limits biospecimen collection to fixed, low-frequency schedules (generally 1-2 collection days/week with step-down to 1 day/week in weeks 5-6 post-trigger) while daily follow-up is restricted to non-invasive clinical monitoring. Participation in the NAVIS protocol does not restrict or prevent enrollment in other Hantavirus-related emergency responses or interventional clinical trials.

Inclusion Criteria:

1. No age restriction.

2. Persons diagnosed with or exposed to Andes Virus (ANDV). Exposure must comply with the national definition of ANDV exposure in each country, or satisfy at least one of the following criteria:

   1. Direct physical exposure to a person with ANDV infection

   2. Environmental and proximity exposure to a person with ANDV infection, i.e.:

      • Prolonged presence in an enclosed or poorly ventilated shared airspace. Note: Prolonged exposure is defined as cumulative exposure of 15 minutes or more within a 24-hour period in a confined space, or shared occupancy of an enclosed environment for more than 2 hours (ECDC).
      • Co-habitation in the same household, room, or cabin (e.g., maritime or shared residential settings).
      • Documented proximity during long-haul travel exceeding 4 hours. Note: Proximity is defined as sitting in an adjacent seat, defined as the same row or within two rows in front or behind. Long haul travel includes flight, bus, car or train. See Box 2 for justification of the 4 hour time threshold.

   3. Occupational or caregiving exposure

      • Provision of direct healthcare or personal care to a person with ANDV infection without the consistent use of recommended Personal Protective Equipment (PPE).
      • Direct handling of potentially contaminated fomites, such as soiled linens, clothing, or bedding used by a confirmed case.
      • Direct handling of laboratory samples form a confirmed case with noncompliance with standard biosafety protocols.

3. Ability to comply with confinement sampling and follow up procedures.

4. Informed consent by participant, parent/legal guardian, or surrogate where allowed and applicable; assent or consent for children aged <18 years or <16 years as per local regulations.

Exclusion Criteria:

• 1. Current imprisonment (quarantine does not count).

Consenting persons of any age who have a confirmed exposure to Andes virus and persons with confirmed Andes virus infection who are placed under confinement or quarantine or clinical care for active Andes virus infection. Participation in the NAVIS protocol does not restrict or prevent enrollment in other Hantavirus-related emergency responses or interventional clinical trials.

Data are available upon reasonable request. The procedures carried out with the French data privacy authority (CNIL, Commission nationale de l'informatique et des libertés) and the european regulation (GDPR) do not provide for the transmission of the database, nor do the information and consent documents signed by the patients. Consultation by the editorial board or interested researchers of individual participant data that underlie the results reported in the article after deidentification may nevertheless be considered, subject to prior determination of the terms and conditions of such consultation and in respect for compliance with the applicable regulations.