Glossary · Epidemiology
Contact case
A person exposed to a confirmed case under conditions likely to enable transmission. Subject to medical surveillance and, depending on risk, appropriate isolation.
A contact case is a person who has been exposed to a confirmed case of an infectious disease under conditions likely to enable transmission, without being ill themselves at the moment of identification. For the MV Hondius hantavirus episode, France had 22 contact cases identified and hospitalised by 12 May 2026 (passengers of the two key flights of 25 April). Contact case status triggers a medical surveillance period whose duration matches the maximum incubation window of the pathogen.
Operational definition #
Generic criteria #
Health authorities (Santé publique France for France, ECDC at European level) define a contact case from several parameters:
- physical proximity to the case (distance, duration),
- environment of the contact (enclosed space vs. outdoors, ventilation),
- type of exposure (presence or absence of protective equipment, direct contact with secretions),
- infectious period of the index case (often symptoms ± day −2 to day +10).
For Andes virus, criteria align with Argentinian and Chilean recommendations: prolonged close contact in an enclosed space with a symptomatic case, household sharing, unprotected care.
Risk levels #
Contacts are classified into several levels by exposure intensity:
- High risk: household contacts, unprotected carers, prolonged shared enclosed space.
- Moderate risk: short exposure or with partial protection.
- Low risk: occasional contact in a large ventilated space.
The measures applied (strict isolation, medical surveillance, simple instructions) follow this classification.
Application to the MV Hondius #
The 22 French contact cases #
On 12 May 2026, Minister of Health Stéphanie Rist announced that the 22 French contact cases identified on the two key flights were "hospitalised or being hospitalised":
- 8 contacts from the Saint Helena → Johannesburg flight of 25 April 2026,
- 14 contacts from the Johannesburg → Amsterdam flight the same day.
Among them, 3 teenagers accompanied by their parents were placed at Pitié-Salpêtrière (Paris 13th). One contact case was transferred from home (Concarneau) to Rennes University Hospital. Another is hospitalised at Marseille University Hospital per the Ministry.
Legal framework #
The decree of 11 May 2026 signed by Prime Minister Sébastien Lecornu governs isolation modalities. Initial hospitalisation lasts about 15 days per the Minister, extended up to 42 days in case of doubt or evolution.
Difference from "contact tracing" #
Contact tracing is the activity by which health authorities identify everyone exposed to a confirmed case. This activity produces contact cases. Once the list is established, each person receives the "contact case" status, with the corresponding measures attached.
End of status #
Contact case status is lifted after the pathogen's maximum incubation period with no symptom onset or biological detection. For Andes virus, this period is 42 days. Beyond that, the risk of developing the disease becomes negligible and the person returns to normal life, without specific surveillance.
Key figures
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22
French contact cases identified as of 12 May 2026 on the two key flights (Saint Helena → Johannesburg and Johannesburg → Amsterdam) and placed in hospital.
Stéphanie Rist / Caroline Semaille press conference, 12 May 2026
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42 days
Maximum surveillance duration for a hantavirus contact case under the French decree of 11 May 2026, aligned with the upper bound of incubation.
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≈ 15 days
Planned initial hospitalisation duration for asymptomatic contact cases per Minister Stéphanie Rist (press conference 12 May 2026).
Standards & references
- Santé publique France — Case and contact definitions — Operational reference definitions for epidemiological investigations in France.
- WHO — Contact tracing guidance — International framework for contact follow-up in outbreaks, adapted by pathogen.
Frequently asked questions
What is a contact case?
A contact case is a person who has been exposed to a confirmed case under conditions likely to enable pathogen transmission, without being ill themselves at the moment of identification. Criteria vary by pathogen: for Andes virus (transmission by aerosols and short-distance human-to-human transmission), a contact case is typically someone who has shared an enclosed space with a symptomatic case for several hours.
What should a hantavirus contact case do?
For the MV Hondius episode, the French decree of 11 May 2026 provides for high-risk contact cases (passengers of the two key flights of 25 April) an initial hospitalisation of about 15 days, with extended medical surveillance up to 42 days if needed. Moderate-risk contact cases receive medical follow-up without systematic hospitalisation, with instructions to immediately report any evocative symptom (fever, myalgias, respiratory signs).
How long does one remain a contact case?
Duration depends on the pathogen. For Andes virus, it spans the maximum incubation period, i.e. up to 42 days (6 weeks) after the last possible exposure. Beyond that, the risk of developing the disease becomes negligible and the person exits contact case status.
What is the difference between 'contact case' and 'contact tracing'?
Contact tracing is the activity by which health authorities identify everyone who has been in contact with a confirmed case. The contact case is the individual status assigned to each of those persons once identified. Contact tracing produces contact cases.
Further reading
- Santé publique France — Contact tracing — Santé publique France (official documentation)
- WHO — Contact tracing guidance — WHO (official documentation)
- DGS-Urgent n°2026-04 — Hantavirus — Direction générale de la Santé (health alert)