Biology subjects

Gaudart, J.

Publications and source records attributed to Gaudart, J..

5 recordsLinked to original sources

bioRxiv2019

The dynamics and interactions of respiratory pathogen carriage among French pilgrims during the 2018 Hajj

Respiratory tract infections are frequent among Hajj pilgrims. We conducted this study to describe the dynamics of the acquisition of respiratory pathogens, their potential interactions and risk factors for possible lower respiratory tract infection symptoms (LRTI) among French pilgrims during the 2018 Hajj. Pilgrims from Marseille who were participating in the Hajj were recruited. Each participant underwent four successive systematic nasopharyngeal swabs before and during their stay in Saudi Arabia. Carriage of the main respiratory pathogens was assessed by PCR. 121 pilgrims were included and 93.4% reported respiratory symptoms during the study period. Polymicrobial carriage was observed in 73.8% samples. The acquisition of rhinovirus, coronaviruses and Staphylococcus aureus occurred soon after arrival in Saudi Arabia and rates decreased gradually after days 5 and 6. In contrast, Streptococcus pneumoniae and Klebsiella pneumoniae carriage increased progressively until the end of the stay in Saudi Arabia. Haemophilus influenzae and Moraxella catarrhalis carriage increased starting around days 12 and 13, following an initial clearance. Influenza viruses were rarely isolated. We observed an independent positive mutual association between S. aureus and rhinovirus carriage and between H. influenzae and M. catarrhalis carriage. Dual carriage of H. influenzae and M. catarrhalis was strongly associated with S. pneumoniae carriage (OR = 6.22, 95%CI [2.04-19.01]). Finally, our model showed that M. catarrhalis carriage was negatively associated with K. pneumoniae carriage. Chronic respiratory disease was associated with symptoms of LRTI. K. pneumoniae, M. catarrhalis-S. aureus and H. influenzae-rhinovirus dual carriage was associated with LRTI symptoms. Our data suggest that RTIs at the Hajj are a result of complex interactions between a number of respiratory viruses and bacteria.\n\nAuthor summaryDespite the recommendation to take individual preventive measures to prevent respiratory tract infections, these infections remain common among Hajj pilgrims. Respiratory pathogens acquired during the Hajj are usually studied individually, although in their natural environment they often compete or coexist with multiple microbial species. A better understanding of polymicrobial interactions in the nasopharynx among Hajj pilgrims is important. Our study describes the dynamics of the acquisition of respiratory pathogens and their potential interactions among pilgrims during the Hajj. We found that polymicrobial carriage was observed in most individuals and that some pathogens associated positively while other did not. Some pathogen associations correlated with symptoms of lower respiratory tract infections.

microbiology↗

bioRxiv2019

Multiscale analysis of a non-periodic epidemic time series using wavelet transform

The aim of the present study was to develop a method for multiscale analysis of non-stationary and non-periodic epidemic time series. Indeed, the epidemiologists may need to know the features, at different resolutions, of short duration outbreaks that did not exhibit periodic cycles. Among of the large number of wavelets, we have developed a continuous wavelet that shows an analogous shape to the Haar wavelet, and leads to precise time localization. We applied the wavelet transform to the cholera epidemic, which began in October 2010 in Haiti. We determined the wavelet spectra of both the cholera case toll and rainfall time series, from September 01, 2010, to November 20, 2012 (812 days). The relationship between case toll and rainfall was analyzed using cross-wavelet spectra at different lags. Cholera case toll scalogram highlighted four epidemic bursts. Cross-wavelet analysis highlighted an absence of relationship between the first epidemic burst and rainfall, but a clear relationship between the following epidemic bursts and rainfall after a 3 to 8 day lag.

epidemiology↗

bioRxiv2018

Targeting hotspots to reduce transmission of malaria in Senegal: modeling of the effects of human mobility

BackgroundIn central Senegal malaria incidences have declined in recent years in response to scaling-up of control measures, but now remains stable, making elimination improbable. Additional control measures are needed to reduce transmission.\n\nMethodsBy using a meta-population mathematical model, we evaluated chemotherapy interventions targeting stable malaria hotspots, using a differential equation framework and incorporating human mobility, and fitted to weekly malaria incidences from 45 villages, over 5 years. Three simulated approaches for selecting intervention targets were compared: a) villages with at least one malaria case during the low transmission season of the previous year; b) villages ranked highest in terms of incidence during the high transmission season of the previous year; c) villages ranked based on the degree of connectivity with adjacent populations.\n\nResultsOur mathematical modeling, taking into account human mobility, showed that the intervention strategies targeting hotspots should be effective in reducing malaria incidence in both treated and untreated areas.\n\nConclusionsMathematical simulations showed that targeted interventions allow increasing malaria elimination potential.

epidemiology↗

bioRxiv2018

The national alert-response strategy against cholera in Haiti: a four-year assessment of its implementation

BackgroundA massive cholera epidemic struck Haiti on October 2010. As part of the national cholera elimination plan, the Haitian government, UNICEF and other international partners launched a nationwide alert-response strategy from July 2013. This strategy established a coordinated methodology to rapidly target cholera-affected communities with WaSH (water sanitation and hygiene) response interventions conducted by field mobile teams. An innovative red-orange-green alert system was established, based on routine surveillance data, to weekly monitor the epidemic.\n\nMethodology/Principal findingsWe used cholera consolidated surveillance databases, alert records and details of 31,306 response interventions notified by WaSH mobile teams to describe and assess the implementation of this approach between July 2013 and June 2017. Response to red and orange alerts was heterogeneous across the country, but significantly improved throughout the study period so that 75% of red and orange alerts were responded within the same epidemiological week during the 1st semester of 2017. Numbers of persons educated about cholera, houses decontaminated by chlorine spraying, households which received water chlorination tablets and water sources that were chlorinated during the same week as cholera alerts significantly increased. Alerts appeared to be an interesting and simple indicator to monitor the dynamic of the epidemic and assess the implementation of response activities.\n\nConclusions/SignificanceThe implementation of a nationwide alert-response strategy against cholera in Haiti was feasible albeit with certain obstacles. Its cost was less than USD 8 million per year. Continuing this strategy seems essential to eventually defeat cholera in Haiti while ambitious long-term water and sanitation projects are conducted in vulnerable areas. It constitutes a core element of the current national plan for cholera elimination of the Haitian Government.

epidemiology↗

bioRxiv2018

Wavelet for binocular vision modeling

In the present study, binocular vision properties were modeled using a single elementary wavelet. Opponent responses (ON-OFF) appeared in the first stages of the neural coding in the retina. This property was assumed to build an adequate wavelet showing a positive part (On) and a negative part (OFF). We have examined the experimental orientation and position disparity given by Bishop. We assumed that the theoretical position disparity was given by a combination of two wavelets for a given orientation disparity {beta}. A change in {beta} implied a change in the magnitude of one of the wavelets and consequently a change in the wavelets combination. There was a close match between the theoretical and experimental position disparity curves according to the changes in orientation disparity.

bioengineering↗