First cases of coronavirus disease 2019 (COVID-19) in France: Surveillance, investigations and control measures, January 2020

Abstract

A novel coronavirus (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2) causing a cluster of respiratory infections (coronavirus disease 2019, COVID-19) in Wuhan, China, was identified on 7 January 2020. The epidemic quickly disseminated from Wuhan and as at 12 February 2020, 45,179 cases have been confirmed in 25 countries, including 1,116 deaths. Strengthened surveillance was implemented in France on 10 January 2020 in order to identify imported cases early and prevent secondary transmission. Three categories of risk exposure and follow-up procedure were defined for contacts. Three cases of COVID-19 were confirmed on 24 January, the first cases in Europe. Contact tracing was immediately initiated. Five contacts were evaluated as at low risk of exposure and 18 at moderate/high risk. As at 12 February 2020, two cases have been discharged and the third one remains symptomatic with a persistent cough, and no secondary transmission has been identified. Effective collaboration between all parties involved in the surveillance and response to emerging threats is required to detect imported cases early and to implement adequate control measures.

Full text

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O
First cases of coronavirus disease 2019 (COVID-19)
in France: surveillance, investigations and control
measures, January 2020
Sibylle Bernard Stoecklin1 , Patrick Rolland2 , Yassoungo Silue3 , Alexandra Mailles1 , Christine Campese1 , Anne Simondon4 ,
Matthieu Mechain , Laure Meurice , Mathieu Nguyen , Clément Bassi³ , Estelle Yamani , Sylvie Behillil , Sophie Ismael , Duc
Nguyen , Denis Malvy9,10 , François Xavier Lescure8,11 , Scarlett Georges¹ , Clément Lazarus12 , Anouk Tabaï13 , Morgane Stempfelet13 ,
Vincent Enouf , Bruno Coignard¹ , Daniel Levy-Bruhl¹ , Investigation team14
1. Santé publique France, Direction des maladies infectieuses, Saint-Maurice, France
2. Santé publique France, Direction des régions, Saint-Maurice, France
3. Santé publique France, Direction des régions, Cellule Régionale Ile-de-France, Paris, France
4. Agence Régionale de Santé Ile-de-France, Paris, France
5. Agence Régionale de Santé Nouvelle-Aquitaine, Bordeaux, France
6. Santé publique France, Direction des régions, Cellule Régionale Nouvelle-Aquitaine, Bordeaux, France
7. Centre National de Référence des virus des infections respiratoires, dont la grippe, Institut Pasteur, Paris, France
8. AP-HP, Hôpital Bichat, Service des maladies infectieuses et tropicales, Paris, France
9. Centre Hospitalier Universitaire de Bordeaux, Bordeaux GeoSentinel Site, Bordeaux, France
10. UMR 1219, Université de Bordeaux, Bordeaux, France
11. Université de Paris, IAME, INSERM, Paris, France
12. Direction Générale de la Santé, Ministère des solidarités et de la santé, Centre opérationnel de réception et de régulation des
urgences sanitaires et sociales, Paris, France
13. Santé publique France, Direction alerte et crise, Saint-Maurice, France
14. The members of the investigation team are listed at the end of the article
Correspondence: Sibylle Bernard-Stoecklin (sibylle.bernard-stoecklin@santepubliquefrance.fr)
Citation style for this article:
Bernar d Stoecklin Sibylle , Rolland P atrick , Silue Yass oungo , Mailles Alexandra , Campese C hristine , Simondon Anne , Mec hain Matthieu , Meurice Laure ,
Nguyen Mathieu , Bassi Cléme nt , Yamani Estelle , Be hillil Sylvie , Ismael Sophie , Nguyen Duc , Malvy Denis , Les cure François Xav ier , Georges Scarlett , Lazar us
Clément , Tabaï Anouk , Stempfelet M organe , Enouf Vincent , Coig nard Bruno , Lev y-Bruhl Danie l , Investigation team . First case s of coronavirus disease 20 19
(COVID- 19) in France: surveillance, investigations a nd control measur es, January 2020 . Euro Surveill . 2020;25(6):pii=200 0094. https://doi.org/10.2807/1560-7917.
ES.2020.25.6.2000094
Article submit ted on 05 Feb 2020 / accep ted on 11 Feb 2020 / published on 13 Feb 2020
A novel coronavirus (severe acute respiratory syn-
drome coronavirus 2, SARS-CoV-2) causing a cluster
of respiratory infections (coronavirus disease 2019,
COVID-19) in Wuhan, China, was identified on 7 January
2020. The epidemic quickly disseminated from Wuhan
and as at 12 February 2020, 45,179 cases have been
confirmed in 25 countries, including 1,116 deaths.
Strengthened surveillance was implemented in France
on 10 January 2020 in order to identify imported cases
early and prevent secondary transmission. Three cat-
egories of risk exposure and follow-up procedure were
defined for contacts. Three cases of COVID-19 were
confirmed on 24 January, the first cases in Europe.
Contact tracing was immediately initiated. Five con-
tacts were evaluated as at low risk of exposure and
18 at moderate/high risk. As at 12 February 2020, two
cases have been discharged and the third one remains
symptomatic with a persistent cough, and no second-
ary transmission has been identified. Effective collab-
oration between all parties involved in the surveillance
and response to emerging threats is required to detect
imported cases early and to implement adequate con-
trol measures.
Background
A novel coronavirus (severe acute respiratory syndrome
coronavirus 2, SARS-CoV-2) causing a cluster of res-
piratory infections (coronavirus disease 2019, COVID-
19) in Wuhan, China, was identified on 7 January 2020
[1]. Twenty-seven patients with pneumonia had initially
been reported, with an epidemiological link to a live
animal market that was closed and disinfected on 1
January [1]. From 20 January, the number of notifica-
tions of cases rose dramatically, and as at 12 Februar y
2020, 45,179 cases of SARS-CoV-2 have been con-
firmed, including 1,116 deaths [2]. Most of the cases
(n = 44,665) were reported in 31 provinces and autono-
mous regions of China and 514 cases were reported in
25 other countries in Asia, Australia, Europe and North
America [2]. To date, the primary source of infection
remains unknown and could still be active. Human-
to-human transmission was observed early after the
emergence of this new virus in China and abroad,
including family clusters and healthcare settings. The
current outbreak dynamics strongly indicate sustained
human-to-human transmission.
Strengthened surveillance of COVID-19 cases was
implemented in France on 10 January 2020. The

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objective of the sur veillance is to identify imported
cases early and to prevent secondary transmission
whether in the community or among healthcare work-
ers (HCW). Investigations are carried out among con-
tacts immediately upon illness onset and a follow-up
procedure is initiated according to the evaluated level
of infection risk.
Here we describe the real-time implementation of this
surveillance scheme for the first three imported cases
of COVID-19 identified in France, who were confirmed
on 24 January 2020 in persons with a recent stay in
Wuhan. Two cases were diagnosed in Paris and one
in Bordeaux. We present data until 12 February on the
follow-up of the cases’ contacts initiated immediately
upon confirmation of infection.
Methods
French surveillance system
In France, according to the COVID-19 surveillance pro-
tocol, physicians suspecting a COVID-19 case have
to contact immediately either the emergency hotline
(SAMU-Centre 15), if the patient is seeking medical
attention from a general practitioner, or a referring
infectious diseases specialist at hospital level.
Together, they evaluate whether the patient matches
the case definition criteria for a possible case (see
below). If they do, the case has to be reported imme-
diately through a 24/7 available phone line to the
Regional Health Agency (Agence régionale de santé,
ARS), which informs without delay the hospital infec-
tion control teams involved in the management of the
patient, the French Public Health Agency (Santé pub-
lique France, SpFrance) and the Ministr y of Health.
A standardised investigation form collecting socio-
demographical information, clinical details and history
of exposure (history of travel to or residence in Wuhan,
China or contact with a confirmed case) is completed
for each possible case at regional level, in collabora-
tion between the clinicians, the ARS and SpFrance.
Data are entered into the secure web-based applica-
tion Voozanoo (Epiconcept, Paris).
Possible cases have to be hospitalised, isolated and
cared for in one of the 38 French referral hospitals
designated by the Ministr y of Health, according to the
guidelines for the management of patients with Middle
East respiratory syndrome (MERS) [3].
For each possible case, respiratory samples from the
upper respiratory tract (nasopharyngeal swabs or
aspirates) and when possible from the lower respira-
tory tract (bronchoalveolar lavage fluid, when indi-
cated, or induced sputum) are collected and sent to
one of the laboratories accredited to perform SARS-
CoV-2-specific real-time RT-PCR. Until 27 January, only
the National Reference Centre for respiratory viruses
(Institut Pasteur, Paris) was able to test for the pres-
ence of the SARS-CoV-2.
Case definition
From 17 to 29 January 2020, a possible case was
defined either as a patient with a severe acute lower
respirator y infection requiring admission to hospital
and with a history of travel to or residence in Wuhan,
T
Definition of a contact and follow-up procedure by level of risk of infection, COVID-19, France, January 2020
Level of risk of
infection Contact definition Follow-up procedure
Negligible risk
Person who had short (< 15 min) contact with a confirmed
case in public settings such as in public transportation,
restaurants and shops; healthcare personnel who treated a
confirmed case while wearing appropriate PPE without any
breach identified.
Neither identification nor information of contacts.
Low risk
Person who had a close (within 1 m) but short (< 15 min)
contact with a confirmed case, or a distant (> 1 m) but
prolonged contact in public settings, or any contact in private
settings that does not match with the moderate/high risk of
exposure criteria.
Contacts are asked to measure their body temperature
twice a day and check for clinical symptoms. In
case of occurrence of symptoms like fever, cough
or dyspnoea, contacts are asked to wear a surgical
mask, isolate themselves and immediately contact the
emergency hotline (SAMU-centre 15) indicating that
they are contacts of a confirmed COVID-19 case.
Moderate/high risk
Person who had prolonged (> 15 min) direct face-to-face
contact within 1 m with a confirmed case, shared the same
hospital room, lived in the same household or shared any
leisure or professional activit y in close proximity with a
confirmed case, or travelled together with a COVID -19 case
in any kind of conveyance, without appropriate individual
protection equipment. Healthcare personnel who treated a
confirmed case without wearing appropriate PPE or with an
identified breach.
In addition to the above, contacts are asked to stay at
home during a 14-day period after their last contact
with the confirmed case while symptomatic and to
avoid contacts with the other persons living in the
same household (or at least wear a surgical mask).
The follow-up consists of an active follow-up through
daily calls from the regional follow-up team organised
by the Regional Health Agency in collaboration with
Santé publique France.
COVID-19: coronavirus disease 2019; PPE: personal protective equipment.

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China in the 14 days before symptom onset, or a
patient with an acute respiratory illness whatever the
severity and with a history of at-risk exposure, mainly
to a confirmed case. A confirmed case was defined as
a possible case with a positive SARS-CoV-2 RT-PCR on
respiratory samples, performed by an accredited labo-
ratory. Testing relied on the real-time RT-PCR procedure
developed by the Charité [4] as well as on the use of
real-time RT-PCR specific for the RdRp gene (four tar-
gets) designed at Institut Pasteur (RdRp-IP).
The case definition was first set up on 10 January and
adapted over time. The detailed case definition used
for the cases presented here as well as the most up-to-
date case definition are available in theSupplement.
Contact and co-exposure tracing
Co-exposed persons are defined as people who shared
the same risks of exposure as a possible or confirmed
case of COVID-19. Contact and co-exposure identifica-
tion is done for all identified possible cases. Contacts
are traced from the date of onset of clinical symptoms
in a case. If the diagnosis of SARS-CoV-2 infection is
confirmed in the index case, active surveillance of con-
tacts/co-exposed persons is initiated immediately.
Three levels of risk of infection are defined for contacts/
co-exposed persons of a possible/confirmed COVID-19
case (Table). Co-exposed persons of a confirmed case
are followed-up according to the same procedure as a
moderate-/high-risk contact. The follow-up procedure
for the contacts/co-exposed persons differs according
to the evaluation of the level of risk of infection (Table).
During the initial implementation phase of the proce-
dure, owing to the limited number of contacts involved,
it was decided to also implement an active follow-up
for low risk contacts.
Patients are inter viewed by the clinicians, with the help
of a translator if needed, who recover relevant informa-
tion on their contacts since onset of clinical symptoms
and the nature and intensity of exposure. The involved
regional health agencies work closely with the regional
entities of Santé publique France (cellules régionales)
in order to implement contact tracing and follow-up.
Santé publique France coordinates the surveillance
at national level in liaison with the national Health
Authorities.
Ethical statement
The investigations were carried out in accordance with
the General Data Protection Regulation (Regulation
(EU) 2016/679 and Directive 95/46/EC) and the French
data protection law (Law 78–17 on 06/01/1978 and
Décret 2019–536 on 29/05/2019). Informed consent to
disclosure of information relevant to this publication
F
Timeline of travel, onset of illness and close contacts of confirmed cases of COVID-19, France, January 2020 (n = 3)
Arrival
in
Wuhan
•Shanghai -
Paris flight
•Paris-
Bordeaux
flight
•GP visit
•Classification as
possible case
•Transfer to
referring
hospital
Laboratory
confirmation of
SARS-CoV-2
infection
Onset
of
illness
Case 1
Shanghai- Paris and
Paris-Bordeaux flights:
13 moderate/high risk
contacts
Taxi: 1 low-
risk contact
GP practice:
1 low-risk contact (GP)
4 moderate/high- risk contacts
(other patients in waitingroom)
Wuhan-
Shanghai
flight
Cases
2 & 3 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Departure
from
WuhanArrival
in Paris
Cases 2&3
•Call to national emergency hotline
•Classification as possible case
•Transfer to referring hospital
Cases 2&3
Laboratory confirmation of
SARS-CoV-2 infection
Visitat Wuhan
hospital(waiting
room at ED)
Case 2
Onsetof
illness
Department store:
1 low- risk contact
(vendor)
Case 3
Onsetof
illness
Rental apartment:
2 low-risk contacts (owners)
1 moderate/high- risk contact (owners’ child)
ICU admission
of case 2
January
Case 2 back
to ID ward
13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
January
ED: emergency depar tment; GP: general practitioner; ICU: intensive care unit; ID: infectious diseases.

4www.eurosurveillance.org
was obtained from the three patients confirmed with
2019-nCoV infection.
Results
Detected confirmed cases
Between 10 January and 24 January (period until confir-
mation of the first cases in France), nine possible cases
were identified in France; among them, three cases
were confirmed with COVID-19.
Case 1 was a 48-year-old male patient living in France.
He was travelling for professional reasons in China in
various cities including Wuhan when he experienced
his first symptoms (fever, headaches and cough) on
16 January. He flew back to Bordeaux, France on 22
January via Shanghai, Qingdao and Paris Charles de
Gaulle airports. He reported wearing a mask during
the flights. He sought medical attention from a general
practitioner on 23 January, where he was suspected
of COVID-19, and was subsequently transferred to the
regional referring hospital in Bordeaux, isolated and
sampled for laborator y confirmation of SARS-CoV-2
infection. Infection was confirmed on 24 January by the
National Reference Centre (Figure). Case 1 tested posi-
tive only for the E gene target when using the Charité
procedure [4] and was positive for all four RdRp-IP tar-
gets with threshold cycles (Ct) in good agreement with
those obtained for the E gene target.
The patient arrived in Wuhan on 13 January, did not
report any visit to markets, exposure to live animals or
contact with sick persons during his stay. No detailed
information is available about the circumstances of
exposure, apart from a visit to family members and
friends on 15 January.
Case 2 was a 31-year-old Chinese male tourist who had
left Wuhan on 18 January and arrived in Paris on 19
January. He developed fever, chills, fatigue, conjuncti-
vitis and cough on 19 January. Case 3 was a 30-year-
old Chinese female tourist who travelled with Case
2. She developed fever, chills, fatigue and cough on
23 January. On 24 January, they were advised by the
Chinese embassy to seek medical attention at the
national hotline (SAMU-centre 15) and were imme-
diately transferred to a regional referring hospital,
isolated and sampled for laborator y confirmation of
COVID-19. Infection with SARS-CoV-2 was confirmed on
24 January for both of them by the National Reference
Centre (Figure). Cases 2 and 3 were positive by RT-PCR
for all targets of the Charité procedure [4] (RdRp Pan
Sarbeco and 2019-nCov probes; E; N) as well for the
four RdRp-IP targets with Ct values in good agreement
with those obtained for the E gene target.
The condition of the male patient deteriorated on 29
January and he was admitted to the intensive care unit
(ICU) the same day. He stayed 72 h in the ICU for non-
invasive oxygen therapy and was transferred back to
infectious diseases ward on 31 January.
Neither of the two cases repor ted any visit to markets,
exposure to live animals or contact with sick persons
during the 14 days before symptom onset. Both vis-
ited a hospital in Wuhan on 16 January for an unrelated
medical condition in Case 3 (Figure).
As at 12 February, Case 1 was afebrile and symptomatic
with a persistent cough. Cases 2 and 3 were not symp-
tomatic any more and were discharged from hospital
on 12 Februar y.
As soon as the infection with SARS-CoV-2 was con-
firmed for the three cases on 24 January, this infor-
mation was immediately released through a press
conference held by the French Minister of Health and
the Chief Medical Off icer. Daily public communication
on the state of the investigations around the cases was
subsequently implemented by the Ministry of Health.
Daily updates were also published on the SpF website.
The three cases were notified to the European
Commission via the Early Warning and Response
System (EWRS) on 26 January, and to the European
Center for Disease Prevention and Control (ECDC)
via the European Surveillance System (TESSy) on 28
Januar y.
Contact and co-exposition tracing
No co-exposed person was identified for Case 1. Two
contacts were evaluated at low risk of infection, the
taxi driver who drove the case from the airport to his
home (30-min drive) and the general practitioner who
took care of the patient before wearing appropriate
personal protection equipment (3-min non-close con-
tact). Seventeen contacts were evaluated at moderate/
high risk of infection. Four of them shared the same
waiting room in the general practitioner’s office while
Case 1 was coughing, seated ca 1–1.5 m away from the
case during 5–30 min. The other 13 contacts were the
persons sitting in the two seats around Case 1 in the
Shanghai–Paris and Paris–Bordeaux flights (Figure).
They were considered at moderate risk of exposure
despite the fact that Case 1 reported wearing a mask
during the whole flight; this was based on the length of
one of the flights (> 6 h) and the fact that it was unclear
whether or not Case 1 removed his mask during short
periods (e.g. meals) and kept the same mask during the
whole flights. None of the contacts of the Shanghai–
Paris flight were French nationals and their contact
tracing was referred to their home countries’ health
authorities. All other identified contacts were evalu-
ated at negligible risk of infection because the con-
tacts were short and/or distant in public settings and
did not imply face-to-face conversations or because
appropriate personal protective equipment (PPE) was
worn by the healthcare personnel who took care of the
patient, including those involved in the transfer from
the general practitioner to the referring hospital.
Cases 2 and 3 stayed together and shared the same
activities during their stay in Paris, and therefore

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shared the same contacts from 23 January (date of ill-
ness onset for Case 3). Three contacts were evaluated
at low risk of infection: the two owners of the apart-
ment rented by the couple and a department store
employee with whom Case 2 reported a distant (> 1 m)
contact during around 20 min on 22 January. The apart-
ment owner’s child who visited Cases 2 and 3 and
was hugged by them was evaluated at moderate/high
risk of infection (Figure). All other identified contacts
were evaluated at negligible risk of infection, as con-
tacts were short and distant in public settings such as
department stores and did not imply face-to-face con-
versations or because appropriate PPE was worn by the
healthcare personnel who took care of the patients.
Follow-up of the identified contacts was initiated
according to the COVID-19 procedure (Table). As at 2
February, two contacts have been classified as pos-
sible cases since the implementation of the follow-up:
A person sitting two seats away from Case 1 during
the Paris–Bordeaux flight, and therefore identified as
a moderate/high risk contact, developed respiratory
symptoms on 27 January and was classified as a possi-
ble case on 31 January and was subsequently excluded
following negative RT-PCR results. Infection with SARS-
CoV-2 was excluded on the same day. A radiology assis-
tant who took care of both Cases 2 and 3 developed
respiratory symptoms on 30 January and was classified
as a possible case on 2 February. This person had been
classified as at negligible risk of exposure, because
she wore appropriate PPE during the whole procedure.
Infection with SARS-CoV-2 was excluded on 2 February.
Follow-up of the contacts ended on 6 February. No
identified contact of the three cases has been con-
firmed with COVID-19.
Discussion
Specific COVID-19 surveillance has been in place in
France since 10 January 2020, 3 days after the iden-
tification of the SARS-CoV-2 in China. The first three
imported cases of COVID-19 in France, the first ones in
Europe, were diagnosed 14 days later, on 24 January.
Rapid and effective collaboration between the cli-
nicians (general practitioners attending the cases,
emergency hotline clinicians (SAMU-centre 15) and
infectious diseases specialists), the National Reference
Centre and the regional and national health authori-
ties has played a crucial role in the system’s capacity
to quickly detect, isolate and investigate those cases
in order to implement adequate control measures. The
surveillance system as well as the control measures
were adapted from those implemented during past
emerging infections that occurred after 2003 (severe
acute respiratory syndrome (SARS), MERS, influenza
A(H1N1)pdm09, Ebolavirus disease), and all involved
parties were already familiar with the system, which
probably favoured its responsiveness.
The case definition of a possible case in use on 24
January was slightly adapted from the one provided
by the World Health Organization (WHO), based on
an epidemiological link to Wuhan, China and a severe
lower acute respiratory disease. It is notewor thy that
the first nine possible cases identified in France,
including the three confirmed cases described here,
displayed mild respiratory symptoms with no sign
of severity at the time of diagnosis. Increasing evi-
dence suggests that mild clinical symptoms could be
more frequent in cases of COVID-19 than with SARS-
CoV and MERS-CoV [5]. Therefore, the case definition
in effect on 24 January lacked sensitivity. This was
counter-balanced by a tendency from the infectious
diseases specialists in charge of classification of sus-
pected cases to privilege the exposure to Wuhan over
the clinical presentation in their decision. However, we
cannot exclude that some COVID-19 cases remained
undetected in France because of the lack of sensitiv-
ity of our case definition. The clinical criteria were
expanded on 4 February to include any lower acute
respiratory disease and the epidemiological criterion
was extended to the whole of China. At that time, the
French laboratory capacities were reinforced from one
to five laboratories able to perform the diagnostics for
COVID-19. Further extension to all 38 referring hospital
laboratories is expected by early to mid-February 2020.
Santé publique France will deploy in early February the
outbreak investigation tool developed by the WHO (Go.
Data [6]) in order to facilitate case data management
and contact tracing at the national and local level in
France.
Contact and co-exposure identification of the three con-
firmed cases had been initiated as soon as they were
classified as possible cases, which facilitated investi-
gations upon confirmation of COVID-19. Confirmation
of the diagnosis was made in the evening of 24 Januar y
and the investigation to retrieve as exhaustively as
possible contacts and co-exposed individuals and
evaluate their level of risk of transmission was started
immediately overnight. Complete transparency of the
investigations was ensured through daily press confer-
ences held by the French health authorities.
Although the follow-up procedure for the contacts/co-
exposed persons used in France slightly differ from
the ECDC and WHO guidelines [7,8], which were not
available at the time of this investigation, it relies on
the same general principles. Contact tracing of the
passengers seated near Case 1 during the two flights
Shanghai–Paris and Paris–Bordeaux was adapted
from the ECDC guidelines for infectious diseases trans-
mitted on aircraft [9]. Even though Case 1 was wearing
a face mask during those flights, we could not exclude
breaches and subsequent risk of transmission to the
persons sitting in the two seats around him.
Because of the current uncertainties about the capac-
ity of SARS-CoV-2 to easily spread from human to
human, the decision to consider a contact as close if
the case–contact distance was between 1 m and 2 m
was made on a case-by-case basis, depending on the
type and leng th of interaction. Through the extensive

6www.eurosurveillance.org
interviews made with the cases and their high com-
pliance to cooperate to the investigation, we believe
that the contacts most at risk have been satisfactorily
identified. All of them could be rapidly contacted and
informed about measures to be taken, which they all
agreed to. However, some contacts were either impos-
sible to trace back (e.g. co-travellers on public trans-
portation) or evaluated as at negligible risk of exposure
because of short and/or distant contacts (e.g. restau-
rant, contacts with cashiers while running errands, vis-
iting museums), although accidental events carrying
the risk of transmission on such occasions, such as an
episode of cough of sneezing, cannot be ruled out.
Moreover, the contact tracing was limited to the period
after onset of illness. However, should the transmis-
sion of SARS-CoV-2 occur during the asymptomatic
phase, we cannot exclude that secondar y transmis-
sion events initiated from the three confirmed cases
remained undetected during the investigations.
Case 3 developed symptoms 4 days after her husband
and 5 days after the couple had left Wuhan. The incu-
bation period of SARS-CoV-2 is currently estimated at
around 3–7 days [5,10,11]. Therefore, she may have
acquired the infection from her husband, although this
cannot be proved.
The active surveillance of close contacts of confirmed
COVID-19 cases and the implementation of control
measures, including home quarantine for those evalu-
ated at moderate/high risk of exposure, decrease the
risk of human-to-human transmission originating from
imported cases and subsequently delay propagation
of the virus in the general population. This allows our
healthcare system to prepare for any further spread of
the epidemic. Besides, the epidemiological and clini-
cal data collected about the confirmed cases and their
contacts will increase our knowledge of COVID-19.
The rapid and collaborative management of the first
imported COVID-19 cases in France highlights the fact
that the French healthcare system is adequately pre-
pared to respond to such emerging diseases threats.
However, this surveillance system is extremely time-
consuming and requires considerable manpower. The
data available on 12 February strongly suggest that
human-to-human transmission of SARS-CoV-2 is fre-
quent, with the reproduction number estimated at 2 to
3 [5,10-14]. Twenty-five countries have already reported
imported cases from China, and several of them have
described autochthonous transmission events [15].
In the case of further spread of SARS-CoV-2 world-
wide, it would soon become impossible to detect all
imported cases and trace their contacts. Especially the
occurrence of large clusters in the same region would
strongly impact on the local health authorities’ capaci-
ties. The surveillance objectives would then need to
evolve from containing the epidemic to mitigating its
medical and societal impact.
As at 12 February, the contacts of the three first con-
firmed cases of COVID-19 in France have been followed
up for the whole 14 days follow-up time after the cases
isolation. No secondary transmission event has been
detected so far despite active follow-up. Given the first
estimations of the SARS-CoV-2 incubation period, the
probability of secondary cases originating from those
three cases is negligible.
Investigation team
Santé publique France, Direction des régions, Cellule
Régionale Nouvelle Aquitaine, Bordeaux, France: Laurent
Filleul, Stéphanie Vandentorren.
Santé publique France, Direction des régions, Cellule
Régionale Auvergne-Rhône-Alpes, Lyon, France: Guillaume
Spaccaferri.
Santé publique France, Direction des régions, Cellule
Régionale Hauts-de-France, Lille, France: Hélène Prouvost.
Centre national de référence Virus des infections respira-
toires, dont la grippe, Institut Pasteur, Paris, France: Mélanie
Albert, Marion Barbet, Angela Brisebarre, Flora Donati,
Sylvie van der Werf.
Agence Régionale de Santé Ile-de-France, Paris, France:
Alexis Ardoin, Marion Dreyer, Karim Tararbit.
Agence Régionale de Santé Nouvelle-Aquitaine, Bordeaux,
France: Matthieu Amodeo, Elodie Couaillier, Pascal Fabre,
Daniel Habold.
Santé publique France, Direction des maladies infectieuses,
Saint-Maurice, France: Didier Che.
AP-HP, Hôpital Bichat, Service des maladies infectieuses
et tropicales, Paris, France: Gisèle Bendjelloul, Marine
Billaudelle Lallemant, Valentine Charachon, Laurène
Deconinck, Diane Descamps, Sandrine Gérard, Nadirha
Houhou, Quentin Le Hingrat, Isabelle Lolom, Jean-Christophe
Lucet, Annabelle Pourbaix, Simon Valayer, Yazdan
Yazdanpanah.
Centre Hospitalier Universitaire de Bordeaux, Service des
maladies infectieuses et tropicales, Bordeaux GeoSentinel
Site, Bordeaux, France: Alexandre Boyer, Benjamin Clouzeau,
Xavier Combes, Arnaud Desclaux, Jean-Michel Dindart,
Alexandre Duvignaud, Isabelle Garrigue, Didier Gruson,
Marie-Edith Lafon, Pauline Perreau, Thierry Pistone, Maxime
Poteau, Eric Tentillier.
Direction Générale de la Santé, Ministère des solidarités
et de la santé, Centre opérationnel de réception et de ré-
gulation des urgences sanitaires et sociales, Paris, France:
Pauline Mathieu
Acknowledgements
We thank Martial Mettendorff, Deputy Director of Santé
publique France for his support in the early phase of the
investigations.
Conflict of interest
None declared.

7www.eurosurveillance.org
Authors’ contributions
All authors provided critical feedback on the manuscript.
Sibylle Bernard Stoecklin, Bruno Coignard and Daniel Levy-
Bruhl wrote the manuscript with input from all authors.
Sibylle Bernard Stoecklin, Patrick Rolland, Alexandra
Mailles, Christine Campese, Didier Che, Clément Lazarus,
Anouk Tabaï, Morgane Stempfelet, Bruno Coignard and
Daniel Levy-Bruhl contributed to the design and implemen-
tation of the sur veillance system, as well as the coordination
between all parties involved in the sur veillance.
Patrick Rolland, Yassoungo Silue, Alexandra Mailles,
Christine Campese, Anne Simondon, Matthieu Mechain,
Laure Meurice, Mathieu Nguyen, Clément Bassi, Estelle
Yamani, Scarlett Georges, as well as all members of the in-
vestigation team contributed to the investigations and the
active surveillance of contacts.
Sophie Ismael, Duc Nguyen, Denis Malvy and François Xavier
Lescure are the clinicians in charge of the three 2019-nCoV
cases and contributed to data collection on clinical history,
exposure and contacts.
Sylvie Behillil and Vincent Enouf contributed to the laborato-
ry confirmation of 2019-nCoV infection in the three impor ted
cases, as well as the testing of samples of possible cases.
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