Objectives. Considering three viral transmission routes: fomite contact, aerial transmission by droplets, and aerial transmission by aerosols, the aerial routes have been the focus of debate about the relative role of droplets and aerosols in SARS-CoV-2 infection. We seek to quantify infection risk in an enclosed space via short-range airborne transmission from droplets and long-range risk from aerosols toward focusing public health measures. Methods. Data from three published studies were analyzed to predict relative exposure at distances of 1 m and farther, mediated by droplet size divided into two bins: larger than 8 microm and smaller than 75 microm (medium droplets) and smaller than 8 microm (small droplets or aerosols). The results at 1 m from an infectious individual were treated as a boundary condition to model infection risk at greater distance. At all distances, infection risk was treated as the sum of exposure to small and medium droplets. It was assumed that number of virions is proportional to droplet volume. Results. The largest infection risk (as exposure to droplet volume) came from medium droplets, close to the infectious individual out to approximately 1 m. Farther away, the largest risk was due to aerosols. For one model, medium droplet exposure disappeared at 1.8 m. Conclusions. Policy concerning social distancing for meaningful infection reduction relies on droplet exposure as a function of distance, yet within this construct droplet size determines respiratory deposition. This two-fold distance effect can be used to evaluate additional measures such as plexiglass barriers and masking. Copyright The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license.

Mild traumatic brain injury (mTBI) or concussion, once thought to be a fairly benign injury with little or no long-term consequences, has been recognized as an important public health concern among children and adolescents. From 2005 to 2009, an estimated 3 million children were seen in emergency departments, and an additional 2 million were seen as outpatients for treatment of mTBI.1 Children with mTBI may experience symptoms that affect cognitive, physical, and psychological function.2 For most children with mTBI, symptoms resolve within 2 to 4 weeks; however, a subset of children will continue to experience symptoms for 3 or more months.3

Importance: Mild traumatic brain injury (mTBI), or concussion, in children is a rapidly growing public health concern because epidemiologic data indicate a marked increase in the number of emergency department visits for mTBI over the past decade. However, no evidence-based clinical guidelines have been developed to date for diagnosing and managing pediatric mTBI in the United States. Objective: To provide a guideline based on a previous systematic review of the literature to obtain and assess evidence toward developing clinical recommendations for health care professionals related to the diagnosis, prognosis, and management/treatment of pediatric mTBI. Evidence Review: The Centers for Disease Control and Prevention (CDC) National Center for Injury Prevention and Control Board of Scientific Counselors, a federal advisory committee, established the Pediatric Mild Traumatic Brain Injury Guideline Workgroup. The workgroup drafted recommendations based on the evidence that was obtained and assessed within the systematic review, as well as related evidence, scientific principles, and expert inference. This information includes selected studies published since the evidence review was conducted that were deemed by the workgroup to be relevant to the recommendations. The dates of the initial literature search were January 1, 1990, to November 30, 2012, and the dates of the updated literature search were December 1, 2012, to July 31, 2015. Findings: The CDC guideline includes 19 sets of recommendations on the diagnosis, prognosis, and management/treatment of pediatric mTBI that were assigned a level of obligation (ie, must, should, or may) based on confidence in the evidence. Recommendations address imaging, symptom scales, cognitive testing, and standardized assessment for diagnosis; history and risk factor assessment, monitoring, and counseling for prognosis; and patient/family education, rest, support, return to school, and symptom management for treatment. Conclusions and Relevance: This guideline identifies the best practices for mTBI based on the current evidence; updates should be made as the body of evidence grows. In addition to the development of the guideline, CDC has created user-friendly guideline implementation materials that are concise and actionable. Evaluation of the guideline and implementation materials is crucial in understanding the influence of the recommendations.

Importance: In recent years, there has been an exponential increase in the research guiding pediatric mild traumatic brain injury (mTBI) clinical management, in large part because of heightened concerns about the consequences of mTBI, also known as concussion, in children. The CDC National Center for Injury Prevention and Control's (NCIPC) Board of Scientific Counselors (BSC), a federal advisory committee, established the Pediatric Mild TBI Guideline workgroup to complete this systematic review summarizing the first 25 years of literature in this field of study. Objective: To conduct a systematic review of the pediatric mTBI literature to serve as the foundation for an evidence-based guideline with clinical recommendations associated with the diagnosis and management of pediatric mTBI. Evidence Review: Using a modified Delphi process, the authors selected 6 clinical questions on diagnosis, prognosis, and management or treatment of pediatric mTBI. Two consecutive searches were conducted on PubMed, Embase, ERIC, CINAHL, and SportDiscus. The first included the dates January 1, 1990, to November 30, 2012, and an updated search included December 1, 2012, to July 31, 2015. The initial search was completed from December 2012 to January 2013; the updated search, from July 2015 to August 2015. Two authors worked in pairs to abstract study characteristics independently for each article selected for inclusion. A third author adjudicated disagreements. The risk of bias in each study was determined using the American Academy of Neurology Classification of Evidence Scheme. Conclusion statements were developed regarding the evidence within each clinical question, and a level of confidence in the evidence was assigned to each conclusion using a modified GRADE methodology. Data analysis was completed from October 2014 to May 2015 for the initial search and from November 2015 to April 2016 for the updated search. Findings: Validated tools are available to assist clinicians in the diagnosis and management of pediatric mTBI. A significant body of research exists to identify features that are associated with more serious TBI-associated intracranial injury, delayed recovery from mTBI, and long-term sequelae. However, high-quality studies of treatments meant to improve mTBI outcomes are currently lacking. Conclusions and Relevance: This systematic review was used to develop an evidence-based clinical guideline for the diagnosis and management of pediatric mTBI. While an increasing amount of research provides clinically useful information, this systematic review identified key gaps in diagnosis, prognosis, and management.

Our coworkers at CDC’s Environmental Public Health Tracking Program | (Tracking Program) come from a | variety of disciplines and backgrounds. They | include epidemiologists, statisticians, database | developers, contract specialists, health communicators, and more. If you look closer at the | people within those specialties, you will find | an even wider array of skills. We have medical | doctors, a veterinarian, educators, graphic designers, and former military personnel, among | others. Every day, each member brings unique | talents, personalities, and backgrounds to produce, maintain, and expand the National Environmental Public Health Tracking Network | (Tracking Network)

CONTEXT: Historically, public health professionals lacked the capacity to evaluate and conduct key investigations into the health of their environment. By bringing together environmental and health effects data from a variety of data sources, the National Environmental Public Health Tracking Network (Tracking) allows users to easily analyze and research the relationships between human health and the environment. OBJECTIVE: As the Tracking Network has matured, its information has been used to guide public health actions, generate hypothesis, and demonstrate relationships between environment and health outcomes. PARTICIPANTS: The Tracking Network is composed of state, local, and national environment and public health partners. SETTINGS: The Environmental Public Health Tracking Network is part of the National Center for Environmental Health at the Centers for Disease Control and Prevention. DESIGN: Tracking standardizes existing data from diverse sources while leveraging technologies and applying sound communication practices to provide a user-friendly interface for the data system by all types of users.