Volume 23, Number 11—November 2017
Evidence-Based Options for Controlling Respiratory Virus Transmission
|Theme||Examples of questions discussed||Lessons learned|
|Theme 1: respiratory virus transmission among humans
||What proportion of respiratory virus transmission occurs through the aerosol (fine particle) route? How many virions are involved in transmission from person to person for different viruses? How do host, viral, and environmental factors influence the routes of transmission? How much viral evolution occurs at the transmission event, versus during the course of infection within a host? Which locations or environments are more supportive to viral transmission? How do all of these issues vary between viruses?
||There is a resurgence of interest in these key questions, with novel methodologies being developed, for example, in air sampling and in investigation of intra-host virus genetic diversity as related to the transmission bottleneck. It was also instructive to learn from the information gained from study of transmission of bacterial infections such as tuberculosis.
|Theme 2: animal models for virus transmission
||What information can be provided from experimental animal models on viral and host factors associated with enhanced transmission potential and on mechanisms of transmission? What is the effect of different inoculation routes on onward transmission? What is the size range of virus-laden particles that mediate influenza transmission among ferrets? Which animal models have preferable characteristics for different viral infections? What additional parameters may be monitored (e.g., by using air sampling devices) during a transmission study to refine the conclusions?
||It was instructive to learn from the animal models used for different viruses. The importance of standardizing how such transmission experiments are carried out is challenging but important for results to be comparable. Use of novel technologies, including new imaging technologies, was discussed.
|Theme 3: determinants of transmission
||What are the viral and host determinants of the emergence of viruses that are efficiently transmissible in humans? What can we learn from surveillance at the animal–human interface, and how should this be done efficiently? What are the best strategies for risk assessment of the many zoonotic transmission events that occur regularly? How should we choose which infections to prioritize the development of medical countermeasures? Can we refine risk assessment algorithms to identify animal viruses of great zoonotic potential?
||The importance of risk assessing data obtained from surveillance was noted. The systematic risk assessment algorithms developed for influenza may serve as a model for risk assessing other emerging respiratory viral pathogens.
|Theme 4: control of respiratory virus transmission||Which nonpharmaceutical measures are more effective in reducing the transmission of respiratory viruses, such as source control measures or environmental controls? What is the risk of transmission in different settings and the impact of control measures on risk? What are the best approaches to control nosocomial transmission of respiratory viruses? What is the potential for new strategies to control respiratory virus transmission? How do all these issues vary between viruses? What are the options for prevention of zoonotic emergence?||Improved understanding of airflow and aerosol dispersion in health care settings may lead to improved engineering designs to reduce risks of nosocomial transmission. Improved understanding of transmission of viruses within domestic livestock trading and marketing systems may allow interventions that reduce risk of emergence of novel emerging pathogens.|
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