Evaluating and optimizing the use of diagnostics during epidemics: Application to the 2017 plague outbreak in Madagascar

During outbreaks, the lack of diagnostic “gold standard” can mask the true burden of infection in the population and hamper the allocation of resources required for control. Here, we present an analytical framework to evaluate and optimize the use of diagnostics when multiple yet imperfect diagnostic tests are available. We apply it to laboratory results of 2,136 samples, analyzed with three diagnostic tests (based on up to seven diagnostic outcomes), collected during the 2017 pneumonic (PP) and bubonic plague (BP) outbreak in Madagascar, which was unprecedented both in the number of notified cases, clinical presentation, and spatial distribution. The extent of this outbreaks has however remained unclear due to non-optimal assays. Using latent class methods, we estimate that 7%-15% of notified cases were Yersinia pestis-infected. Overreporting was highest during the peak of the outbreak and lowest in the rural settings endemic to Yersinia pestis. Molecular biology methods offered the best compromise between sensitivity and specificity. The specificity of the rapid diagnostic test was relatively low (PP: 82%, BP: 85%), particularly for use in contexts with large quantities of misclassified cases. Comparison with data from a subsequent seasonal Yersinia pestis outbreak in 2018 reveal better test performance (BP: specificity 99%, sensitivity: 91%), indicating that factors related to the response to a large, explosive outbreak may well have affected test performance. We used our framework to optimize the case classification and derive consolidated epidemic trends. Our approach may help reduce uncertainties in other outbreaks where diagnostics are imperfect.

Measles in Vaccinated People: Epidemiology and Challenges in Surveillance and Diagnosis in the Post-Elimination Phase. Spain, 2014–2020

The MMR vaccination program was introduced in Spain in 1981. Consistently high vaccination coverage has led to Spain being declared free of endemic measles transmission since 2014. A few imported and import-related cases were reported during the post-elimination phase (2014 to 2020), with very low incidence: three cases per million of inhabitants a year, 70% in adults. In the post-elimination phase an increasing proportion of measles appeared in two-dose vaccinated individuals (up to 14%), posing a challenge to surveillance and laboratory investigations. Severity and clinical presentation were milder among the vaccinated. The IgM response varied and the viral load decreased, making the virus more difficult to detect. A valid set of samples (serum, urine and throat swab) is strongly recommended for accurate case classification. One third of measles in fully vaccinated people was contracted in healthcare settings, mainly in doctors and nurses, consistent with the important role of high intensity exposure in measles breakthrough cases. Surveillance protocols and laboratory algorithms should be adapted in advanced elimination settings. Reinforcing the immunity of people working in high exposure environments, such as healthcare settings, and implementing additional infection control measures, such as masking and social distancing, are becoming crucial for the global aim of measles eradication.

Snakebites in Rural Areas of Brazil by Race: Indigenous the Most Exposed Group

Animal stings are environmental hazards that threaten millions annually and cause a significant socioeconomic impact. Snakebite envenoming affects 2.7 million people globally every year, mostly the poorest and rural communities, with approximately 27,000 annual cases in Brazil. This study’s objective is to identify the most exposed racial group for snakebites in rural areas of Brazil and analyze possible differences in the outcome of an accident. A retrospective epidemiological study was conducted using a database of rural snakebite cases from Brazil’s Ministry of Health (2017). Descriptive analysis and a regression model were performed to examine the association of bad outcomes after a snakebite with several covariables. While mixed-race individuals presented the highest number of cases (61.79%), indigenous and white populations were the racial groups with the highest and lowest exposure rates (194.3 and 34.1 per 100,000 population, respectively). The fatality rate was 3.5 times higher in the indigenous population compared to the white population. In the multivariable model, the number of hours between the accident and health care received and the case classification suggested an association with a bad outcome. Snakebite is prominent in Brazil, particularly among indigenous groups. Antivenom is available in the Brazilian Health System; however, efforts need to be made for decentralization.

Foci Classification in Malaria Elimination Setting: A Conceptual Framework

The concept of malaria elimination is becoming more and more important. Among countries with malaria transmission in 2015, eliminating malaria from 35 countries including those in the Great Mekong has been targeted by 2030. In the journey to elimination through the foci classification procedure, a limited number of “hotspots” among a large number of foci should be precisely defined to be covered by effective controlling measures. There is a common consensus that foci and case classification are fundamental principles of malaria elimination and prevention of reintroduction. However, there are numerous ambiguities and controversies in almost all aspects of foci classifications. These uncertainties result in misclassification that, in turn, wastes lives, time, and money thereby violating value for money principles. New progress in the literature such as ignoring “new potential” foci and using the class of “active foci” instead of the two classes of “new active” and “residual active” is in opposition to the philosophy of foci classification. In this paper, we seek to elaborate the controversies and ambiguities around the concept of foci classification and ultimately suggest some solutions. Some of the ways forward include: (a) foci classification should be done by parasite type; (b) a set of foci classes includes “cleared up”, “new potential”, “new active”, “residual active”, and “residual nonactive”; (c) The number and population of various foci classes should be regularly updated and monitored as the basis for measuring progress toward elimination and it can be considered as the basis for needs assessment and planning response; (d) The coverage and completeness of the controlling interventions by foci classes should be regularly monitored; and (e) The criteria for early detection of outbreaks should be defined. Furthermore, two applicable models for foci classification by parasite have been proposed.

Pharmaceutical Data Search by Decision Trees

The number of information concerning the drugs that any professional of health must control in practice and the transformations which they undergo, make the regulation or the administration of drugs difficult for a pregnant woman. Techniques of excavation of data were developed to lead a model of classification of data according to precise criteria. One of the most used of is the technique of the decision trees, a method making it possible to predict the membership of an individual to a class according to his characteristics; it is based primarily on the relevant attributes of the data base of the field to which it is applied. In our case classification of managed drugs or not with the pregnant woman will be done according to quarters of the pregnancy. The results of this technique will help the professionals of health to take a decision, to make a good regulation, to decrease the accidents related to the catch of inadequate drugs at the period of pregnancy with less risks for the child.