A scheme for detecting every single target molecule with surface-enhanced Raman spectroscopy.

Surface-enhanced Raman spectroscopy (SERS) is now a well-established technique for the detection, under appropriate conditions, of single molecules (SM) adsorbed on metallic nanostructures. However, because of the large variations of the SERS enhancement factor on the surface, only molecules located at the positions of highest enhancement, so-called hot-spots, can be detected at the single-molecule level. As a result, in all SM-SERS studies so far only a small fraction, typically less than 1%, of molecules are actually observed. This complicates the analysis of such experiments and means that trace detection via SERS can in principle still be vastly improved. Here we propose a simple scheme, based on selective adsorption of the target analyte at the SERS hot-spots only, that allows in principle detection of every single target molecule in solution. We moreover provide a general experimental methodology, based on the comparison between average and maximum (single molecule) SERS enhancement factors, to verify the efficiency of our approach. The concepts and tools introduced in this work can readily be applied to other SERS systems aiming for detection of every single target molecule.

Introducing cobalt as a potential plasmonic candidate combining optical and magnetic functionalities within the same nanostructure.

The control of magnetic properties at the nanoscale is a current topic of intense research. It was shown that combining both magnetic and plasmonic nanoparticles (NPs) led to the improvement of their magneto-optical signal. In this context, common strategies consist of the design of bimetallic NPs. However, the understanding of the physics leading to the coupling between magnetic and plasmonic NPs is lacking, preventing any significant progress for the development of future photonic devices. In this article, we propose to focus our attention on an efficient and commonly used magnetic metal, cobalt, and evaluate its plasmonic properties at the nanoscale through the use of NP regular arrays, as a potential candidate combining both optical and magnetic functionalities within the same metal. We show that such NPs display plasmonic properties within a large spectral range from the UV to the NIR spectral range, with efficient quality factors, when the inter-particle distance is properly selected. These as-fabricated simple materials could find applications in integrated photonic devices for telecommunications.

Cost analysis of an integrated disease surveillance and response system: case of Burkina Faso, Eritrea, and Mali.

BACKGROUND: Communicable diseases are the leading causes of illness, deaths, and disability in sub-Saharan Africa. To address these threats, countries within the World Health Organization (WHO) African region adopted a regional strategy called Integrated Disease Surveillance and Response (IDSR). This strategy calls for streamlining resources, tools, and approaches to better detect and respond to the region's priority communicable disease. The purpose of this study was to analyze the incremental costs of establishing and subsequently operating activities for detection and response to the priority diseases under the IDSR. METHODS: We collected cost data for IDSR activities at central, regional, district, and primary health care center levels from Burkina Faso, Eritrea, and Mali, countries where IDSR is being fully implemented. These cost data included personnel, transportation items, office consumable goods, media campaigns, laboratory and response materials and supplies, and annual depreciation of buildings, equipment, and vehicles. RESULTS: Over the period studied (2002-2005), the average cost to implement the IDSR program in Eritrea was $0.16 per capita, $0.04 in Burkina Faso and $0.02 in Mali. In each country, the mean annual cost of IDSR was dependent on the health structure level, ranging from $35,899 to $69,920 at the region level, $10,790 to $13,941 at the district level, and $1,181 to $1,240 at the primary health care center level. The proportions spent on each IDSR activity varied due to demand for special items (e.g., equipment, supplies, drugs and vaccines), service availability, distance, and the epidemiological profile of the country. CONCLUSION: This study demonstrates that the IDSR strategy can be considered a low cost public health system although the benefits have yet to be quantified. These data can also be used in future studies of the cost-effectiveness of IDSR.

Trained district health personnel and the performance of integrated disease surveillance in the WHO African region.

BACKGROUND: African countries have intensified in-service training on Integrated Disease Surveillance and Response (IDSR) for district and facility health personnel to strengthen their disease surveillance systems. Eight countries evaluated their experiences and lessons in the implementation of IDSR. METHODOLOGY: We conducted a secondary analysis of the evaluation reports to assess the impact of training of district health personnel on the performance of disease surveillance systems. We developed indicators to assess the potential impact of their training on the timeliness and completeness of reporting, the data analysis of priority diseases at the district and health facility levels and supervision and feedback at the district level FINDINGS: Training approaches implemented included cascade, on-job, pre-service and fast track training on detection, reporting and data analysis. The overall proportion of health facilities with one or two personnel trained varied from 52% to 89% and the knowledge of the health personnel for epidemic-prone diseases ranged from 52% to 78%. All the countries met the threshold of 60% of health personnel in their districts trained in IDSR. The evidence from data analysis at the district level was more than 60% and the timely reporting and completeness of health facilities 70% and 92%, respectively. Supervision of health facilities ranged from 75% to 100%, however feedback was not provided on a regular basis CONCLUSIONS: Trained district personnel are key in the performance of the national IDSR. This review shows that training of district health personnel coupled with sustainable supervision and feedback, reliable communication and availability of simplified reporting tools can contribute to improved performance of national diseases surveillance systems.

Lessons learned during active epidemiological surveillance of Ebola and Marburg viral hemorrhagic fever epidemics in Africa.

OBJECTIVE: To review epidemiological surveillance approaches used during Ebola and Marburg hemorrhagic fever epidemics in Africa in the past fifteen years. Overall, 26 hemorrhagic epidemic outbreaks have been registered in 12 countries; 18 caused by the Ebola virus and eight by the Marburg virus. About 2551 cases have been reported, among which 268 were health workers (9,3%). METHODS: Based on articles and epidemic management reports, this review analyses surveillance approaches, route of introduction of the virus into the population (urban and rural), the collaboration between the human health sector and the wildlife sector and factors that have affected epidemic management. FINDINGS: Several factors affecting the epidemiological surveillance during Ebola and Marburg viruses hemorrhagic epidemics have been observed. During epidemics in rural settings, outbreak investigations have shown multiple introductions of the virus into the human population through wildlife. In contrast, during epidemics in urban settings a single introduction of the virus in the community was responsible for the epidemic. Active surveillance is key to containing outbreaks of Ebola and Marburg viruses CONCLUSIONS: Collaboration with those in charge of the conservation of wildlife is essential for the early detection of viral hemorrhagic fever epidemics. Hemorrhagic fever epidemics caused by Ebola and Marburg viruses are occurring more and more frequently in Sub-Saharan Africa and only an adapted epidemiological surveillance system will allow for early detection and effective response.

The first large epidemic of meningococcal disease caused by serogroup W135, Burkina Faso, 2002.

In 2001 a significant proportion of cases of meningococcal meningitis toward the end of a serogroup A epidemic in Niger and Burkina Faso was found to be caused by serogroup W135 meningococci. The World Health Organization put in place in several African countries an extended surveillance scheme in preparation for a possible epidemic situation. In January 2002, the first large epidemic of meningococcal disease caused by serogroup W135 started in Burkina Faso, resulting in more than 12,000 cases and 1400 deaths. We report here the results of the laboratory-based surveillance and the characteristics of the epidemic clone.