Concepts for controlling microbial threats to human health

Cross-sectional model of a coronavirus. Source:


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With the spread of novel coronavirus (COVID-19) many persons not trained in infectious disease transmission dynamics may not completely understand how and why public health officials implement interventions. Understanding transmission control measures requires some basic understanding of infectious diseases, infection control, clinical medicine, and mathematical epidemiology.

We summarize the concepts as

  1. Transmission mechanisms (biology, behaviors, environments)
  2. Transmission dynamics (incidence, prevalence, attack proportion, case fatality proportion)
  3. Transmission containment (strategies, control measures)

From these concepts emerge core strategies that are used to design control measures. We developed a 1-page summary (“cheat sheet”) of these concepts to serve as a conceptual playbook (Figure 1). The cheat sheet and tutorial are available here:

Model for Preventing and Controlling Infectious Disease
Figure 1: Model for Preventing and Controlling Infectious Diseases

Of course, the operational details are critical to successful implementation of containment strategies. Here are key web resources to study how these concepts are deployed in the current COVID-19 epidemic:

Center for Disease Control and Prevention (CDC):

Tomás J. Aragón
Health Officer, City & County of San Francisco; Director, Population Health Division

I exercise legal authority to protect and promote equity and health, and I direct core public health services.

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