key: cord-304787-fohgekp4
authors: Prazuck, Thierry; Giaché, Susanna; Gubavu, Camelia; Colin, Mathilda; Rzepecki, Vincent; Sève, Aymeric; Pialoux, Gilles; Hocqueloux, Laurent
title: Investigation of a family outbreak of COVID-19 using systematic rapid diagnostic tests raises new questions about transmission
date: 2020-06-29
journal: J Infect
DOI: 10.1016/j.jinf.2020.06.066
sha: 
doc_id: 304787
cord_uid: fohgekp4

nan

We read with interest the letter by Jiang and colleagues who described the spread of SARS-CoV-2 in a family cluster in China. 1 Herein, we describe the epidemiological, clinical and biological characteristics of 30 households in close contact with SARS-CoV-2-infected members, living in a confined environment during the French national lockdown. This report highlights important issues about transmission.

Two families (26 and 4 members, respectively) were included in the study. During the 5 days before the French national lockdown, both families moved from their usual Parisian residence to a closed property in the countryside, composed by 3 neighboring houses (A, B and C) in a park. House A was inhabited by 8 persons from a single family, including 3 couples who shared their bed for at least 4 days after the onset of symptoms. In house B, there were 2 families composed of 9 persons. There were 2 married couples who shared their bed during all the time, even in presence of symptoms. In house C, there were 2 families composed of 13 persons. There were 4 married couples who shared the bed until the hospitalization of the 84-year-old subject for severe SARS-CoV-2 infection. With the exception of the elderly couple who already lived in House C, all the remaining people arrived there between March 12 and 16, before the beginning of the national lockdown (March 17, 2020).

Thereafter, all residents were not allowed to quit until the end of lockdown (May 11, 2020). During the first week of cohabitation there were regular and close contacts among households from the 3 houses. Since the occurrence of the first 3 symptomatic cases, contacts among the 3 houses were reduced although they indirectly continued through children displacements.

Within their stay, all residents were clinically examined at least once. RT-PCR testing of SARS-CoV-2 was performed for symptomatic cases. 2 Serologic testing using the approved COVID-PRESTO® rapid diagnostic tests 3 (AAZ, Boulogne-Billancourt, France), detecting both IgM and IgG, was performed on whole blood finger-stick more than 45 days after the onset of symptomatic cases on all the 30 subjects. Population characteristics are detailed in Table 1 .

The first diagnosed case was a 67-year-old man (resident #1) living in the house A and referring to the Infectious Diseases outpatient clinic on March 17 for cough, fever and asthenia for 4 days.

Investigation of the cluster began soon after resident #1 was formally diagnosed with COVID-19. This first recognized case was acquired before the arrival of resident #1, who probably transmitted the infection to resident #3 (his son-in-law) after arrival at home A. No transmission occurred between husbands and wives in house A although couples moved to separated rooms only 4 days after the onset of symptoms of the index case. As resident #6 was asymptomatic with IgG+/IgM-, it is not sure that she was infected prior or after her arrival at home A. In house B, a single resident (#9) was found to be infected with COVID-19. He probably acquired infection by the end of February after a close contact with a confirmed case in Paris. Symptoms occurred on March 12, four days before arriving at home B, with cough, asthenia, anosmia, cutaneous lesions lasting one week. As the COVID-19 cluster was unrecognized at this time, he was not separated from the rest of the residents, he continued to share the bedroom with his wife and he had remarkably close contacts with his children. Although he had close contacts with all his family and friends during all the symptomatic phase, no secondary cases occurred. In house C, resident #22 was the first (retrospectively) identified with COVID-19. She developed typical symptoms (cough, fever, headache and asthenia) on March 10 when she was in Paris. At her arrival in house C on March 13, she still had mild symptoms. She probably infected her husband, father and mother (residents #23, #18 and #19, respectively). Resident #18 developed a severe lower respiratory tract infection and was hospitalized for 2 weeks while. Resident #23 developed a moderate cough for two days. Resident #20 may have been infected by resident #23, during a round trip by car on March 17, when resident #23 was already symptomatic. Resident #20 presented with diarrhea, cough and fever lasting four days. Figure 1 shows distribution of residents in each house, kinship, confirmed COVID-19 cases and the temporal occurrence of each case.

Overall, 9 out of 30 residents (30%) were diagnosed with COVID-19. We identified 3 independent index cases (residents #1, #9, #22) that infected 6 secondary cases: 2 in house A, none in house B and present were infected, although they had very closed contacts with their infected parents. Among the 9 married couples who were present, all shared the same bed at least some days after the onset of symptoms or during all the time of disease. Nevertheless, partners were infected in only 3 couples, partners remained discordant in 5, and none of the partners were infected in 1. After careful questioning, discordant couples confirmed they had continued sexual activity during the period at risk of contagiousness of their partner.

This cluster investigation illustrates important facts concerning SARS-CoV-2 transmission. First, as no case occurred in children we are confident they did not participate in the viral transmission network, either within or between houses. This supports the hypothesis that, usually, children are not asymptomatic carriers who transmit the SARS-CoV-2. 4-6 Second, there was a limited transmission of SARS-CoV-2 among couples, even though discordant couples continued to be sexually active during the contagious period of the infected partner. To our knowledge, there are no similar reports published to date. If the determinants of such a "resistance" to SARS-CoV-2 remain uncertain, some of our results (data not shown) allow us to speculate about a potential role of a genetic factor, currently under investigation. 

Characteristics of a family cluster of Severe Acute Respiratory Syndrome Coronavirus 2 in Henan

Verrill Kelly A. How to Obtain a Nasopharyngeal Swab Specimen

Evaluation of performance of two SARS-CoV-2 rapid whole blood finger-stick IgM-IgG combined antibody tests

Spread of SARS-CoV-2 in the Icelandic Population

COVID-19 in children: the link in the transmission chain

Nasal Gene Expression of Angiotensin-Converting Enzyme 2 in Children and Adults

This study was approved by the local institutional review board. A written informed consent was obtained from all patients. 
