key: cord-0978682-bj7texaa
authors: Ly, Tran Duc Anh; Hoang, Van Thuan; Goumballa, Ndiaw; Louni, Meriem; Canard, Naomie; Dao, Thi Loi; Medkour, Hacene; Borg, Audrey; Bardy, Kevin; Esteves-Vieira, Véra; Filosa, Véronique; Davoust, Bernard; Mediannikov, Oleg; Fournier, Pierre-Edouard; Raoult, Didier; Gautret, Philippe
title: Variations in respiratory pathogen carriage among a homeless population in a shelter for men in Marseille, France, March–July 2020: cross-sectional 1-day surveys
date: 2021-02-13
journal: Eur J Clin Microbiol Infect Dis
DOI: 10.1007/s10096-020-04127-9
sha: ecb3216132edec5ef9d55d667682b93e9472f672
doc_id: 978682
cord_uid: bj7texaa

We aimed to compare respiratory pathogen carriage by PCR during three different time periods in 2020 in sheltered homeless people in Marseille, France. The overall prevalence of respiratory pathogen carriage in late March–early April (69.9%) was significantly higher than in late April (42.3%) and mid-July (45.1%). Bacterial carriage significantly decreased between late March–early April and late April. SARS-CoV-2 was detected only in late March–early April samples (20.6%). Measures aiming at mitigating SARS-CoV-2 transmission were effective and also impacted bacterial carriage. Seasonal variations of bacterial carriage between winter and summer in this population were not marked. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10096-020-04127-9.

Crowded conditions in shelters without specific preventive measures could facilitate the transmission of respiratory pathogens [1] [2] [3] . In previous studies conducted by our team during the winter over the past two decades, we observed a high prevalence of respiratory symptoms and signs [1] and high carriage rates of both respiratory viruses [2] and bacteria [3] among a sheltered homeless population in Marseille, France. Seasonal variations of the microbial community in the airways of adults and children have been described in other populations [4, 5] .

Homeless shelter A contains 283 places including emergency (overnight stay) units with a rapid turnover (7-14 nights) and special (permanent stay) units dedicated to highrisk sedentary homeless persons characterized by a high level of poverty, poor hygiene, alcoholism, mental illness and chronic diseases. In Marseille, the first case of COVID-19 in the general population was diagnosed on 3 March 2020. The epidemic peaked during the first week of April, remained active until the end of April and strongly reduced in July [6] . All residents were placed under strict lockdown from 17 March to 11 May, in 2020, as for the entire French population. Based on the preliminary information that some homeless persons from this shelter presented with COVID-19 symptoms, we organized a screening campaign in collaboration with the staff in charge of these shelters. In this study, we aimed to compare clinical respiratory symptoms and respiratory viral and bacterial carriage during three different time periods (in early period of lockdown, in late period of lockdown, in summer) in the same population of sheltered homeless people in Marseille, France. [11] ), together with internal controls (human beta-actin gene [12] and MS2 phage [7] ) as previously described. HCoV-positive samples were subsequently screened for HCoV-HKU1, HCoV-NL63, HCoV-229E and HCoV-OC43 [2] . Results with cycle threshold (CT) ≤ 35 were considered positive.

Statistical analysis Statistical procedures were performed using STATA 11.1. We used Pearson's chi-square or Fisher's exact tests to compare differences of percentage between two groups of individuals where appropriate. The chi-square test for R by C table was used to compare the differences of proportions within three groups. Means of quantitative data within three groups were compared using analysis of variance (ANOVA test). A two-sided p value of less than 0.05 was considered statistically significant.

Overall, 207 homeless persons agreed to participate and underwent nasal sampling at least on one date, accounting for an estimated 56% of homeless people living at the shelter at the time of enrolment. Of those, 126 were recruited in late March-early April, 111 in late April and 71 in mid-July. Only 17 of 207 (13.4%) individuals were tested three times (Supplementary Figure 1) .

Demographics, chronic conditions and clinical status (Table 1) All individuals were male with a mean age of 47.1 years, originating mostly from the African continent (67.6%). There was no significant variation of age and birthplace according to sampling time. Regarding clinical findings, the highest symptom prevalence was observed in late Marchearly April, with 38.1% reporting at least one respiratory symptom or fever. The symptom prevalence decreased to 11.7% in late April and 5.6% in mid-July. Prevalence of respiratory pathogens by real-time PCR (Fig. 1) Overall, 167 (54.2% of total samples, n = 308) tested positive for at least one pathogen (Fig. 1) . M. catarrhalis was the pathogen most frequently detected, with 27.6% of all samples testing positive, followed by S. aureus (17.2%) and H. influenzae (7.5%). Among the viruses, high positivity rates were observed for SARS-CoV-2 (8.4%). The percentage of individuals who tested positive for HRV was 3.6%; other viruses were negative. The overall prevalence of respiratory pathogen carriage in late March-early April (69.9%) was significantly higher than in late April (42.3%) and mid-July (45.1%). Bacterial carriage significantly decreased between late March-early April and late April. SARS-CoV-2 was detected only in late March-early April samples (20.6%). Bacterial carriage was not significantly different between SARS-CoV-2 positive samples (42.7%) and SARS-CoV-2 negative samples (47.1%), with p value = 0.78. No deaths were reported during the study period.

Measures to mitigate the risk of transmission in the homeless population that were undertaken included strict lockdown, avoiding gatherings of persons at the shelter, wearing a mask in public, maintaining distance from others, washing hands with soap and water frequently and for at least 20 s, practicing cough etiquette and avoiding touching the eyes, nose or mouth with unwashed hands. Individuals testing positive for SARS-CoV-2 were moved to special facilities for COVID-19 homeless patient isolation or kept in single rooms at the shelter with strict isolation measures for 14 days.

As in previous studies conducted in sheltered homeless populations in Marseille, we observed high rates of bacterial colonization and comparatively very low rates of common virus carriage [3] . High carriage rates of SARS-CoV-2 were observed, confirming that homeless people are at high risk for COVID-19 [13, 14] . The secondary bacterial infections are potentially common among SARS-CoV-2 (or SARS-CoV or MERS-CoV) patients [15] but the bacterial carriage did not significantly differed between SARS-CoV-2 carriers and those negative for this virus in our study.

Measures aimed at mitigating SARS-CoV-2 transmission were very effective, and no new case was documented during the last two sampling campaigns. Similar shelter-based infection control measures were recommended in Boston, USA [16] . In a UK study, the multivariable probabilistic sensitivity analysis suggested that such measures could avoid many deaths and infections in homeless shelters [17] . Interestingly, a transient but significant decrease of bacterial carriage was also observed in April. To the best of our knowledge, no study has reported the effects of measures aimed at mitigating SARS-CoV-2 transmission on the variation of respiratory bacterial carriage in the context of homeless shelters. Bacterial colonization tended to increase again in July, suggesting that seasonal variations of bacterial carriage between winter and summer in this population are not marked. Our study has several limitations. Notably, the population was not randomly and homogenously recruited. The proportion of paired samples was very low, due to the high mobility of this group and a low acceptance rate during the last two sampling campaigns. The medical histories of participants and individual adherence to preventive measures were not documented.

Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s10096-020-04127-9.

Contribution of a shelterbased survey for screening respiratory diseases in the homeless

The viral etiology of an influenza-like illness during the 2009 pandemic

Epidemiology of respiratory pathogen carriage in the homeless population within two shelters

Seasonal variations in nasopharyngeal carriage of respiratory pathogens in healthy Italian children attending day-care centres or schools

The descriptive epidemiology of Streptococcus pneumoniae and Haemophilus influenzae nasopharyngeal carriage in children and adults in Kilifi District

COVID-19 [COVID-19: epidemiological update of

Santé Publique France

The dynamics and interactions of respiratory pathogen carriage among French pilgrims during the

The presence of Acinetobacter baumannii DNA on the skin of homeless people and its relationship with body lice infestation

Rapid viral diagnosis and ambulatory management of suspected COVID-19 cases presenting at the infectious diseases referral hospital in Marseille

Infectious disease symptoms and microbial carriage among French medical students travelling abroad: a prospective study

World heath organisation (2020) Detection of 2019 novel coronavirus (2019-nCoV) in suspected human cases by RT-PCR

Complementarity between targeted real-time specific PCR and conventional broadrange 16S rDNA PCR in the syndrome-driven diagnosis of infectious diseases

Self-isolation and the homeless population

COVID-19 precautions: easier said than done when patients are homeless

Secondary bacterial infections in patients with viral pneumonia

Addressing COVID-19 among people experiencing homelessness: description, adaptation, and early findings of a multiagency response in Boston

COVID-19 among people experiencing homelessness in England: a modelling study

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Acknowledgements We thank our co-workers at the University Hospital Institute (IHU) who assisted us in recruiting, interviewing and examining participants and collecting samples.

Authors' contributions TD and PG contributed to experimental design,