# Contact tracing

> Public health process of identifying, informing and following up people who have been in contact with a confirmed case of an infectious disease, to break transmission chains.

Canonical source: https://hantatracker.fr/en/glossary/contact-tracing/

**Aliases**: contact tracing, case contact tracing, tracing of contacts

**Contact tracing** is a fundamental public health process that consists of identifying, informing and following up people who have been in contact with a confirmed case of an infectious disease, in order to break transmission chains. It is being applied in 10 countries for the passengers and crew of the MV Hondius, under joint WHO/ECDC international coordination.

## Principle and purpose

### Three objectives

Contact tracing pursues three simultaneous objectives: (1) **early detection** of contacts who develop symptoms, so they can be treated quickly and mortality limited; (2) **breaking secondary transmission** by isolating symptomatic contacts before they themselves become contagious; (3) **documenting the outbreak** to understand transmission chains and adjust measures.

### Method

The WHO distinguishes three steps: *identification* (listing contact persons through interviews with the case), *enumeration* (qualifying the nature and duration of contact) and *follow-up* (regular monitoring during the maximum incubation period, isolation if symptoms appear). This method is used for tuberculosis, measles, Ebola, COVID-19 and now Andes hantavirus.

## Application to the MV Hondius

### Scope

Authorities identified 149 people on board (passengers and crew) of **23 nationalities**. Contact tracing is coordinated internationally by the WHO and ECDC, and operated by the national health authorities of each country of residence. As of 10 May 2026, **10 countries** are running an active contact-tracing operation: Belgium, France, Greece, Ireland, Poland, Portugal, Spain, United States, Canada, Australia.

### Surveillance duration

Surveillance extends over **42 days** from the last possible exposure, the maximum known incubation period for Andes virus. This duration is three times that used for COVID-19 (14 days), mobilising health resources for nearly a month and a half.

### Individual instructions

Identified contacts are asked to: monitor their temperature daily, seek care immediately if fever, headache or respiratory symptoms appear, and systematically mention their hantavirus exposure to their care provider. In France, 15 remains the emergency number; people can also contact their family doctor or their Regional Health Agency (ARS).

## Legal and ethical framework

### Data protection

In Europe, contact tracing is governed by the **General Data Protection Regulation (GDPR)**. Health authorities only collect the information needed (identity, contact details, symptoms), for a strictly defined purpose (health follow-up), and destroy it at the end of the surveillance period. No data is shared for commercial or profiling purposes.

### International cooperation

The MV Hondius contact tracing illustrates the importance of the **International Health Regulations** (IHR 2005), the WHO legal framework that requires Member States to report events of international public health concern and to cooperate in managing them. The operation coordinated by the WHO and ECDC is an example of the IHR in action.