Re-assessment of mitigation strategies for deliberate releases of anthrax using a real-time outbreak characterization tool

Responding rapidly and appropriately to a covert anthrax release is an important public health challenge. A methodology to assist the geographical targeting of such a response has recently been published; as have a number of independent studies that investigate mitigation strategies. Here, we review and combine some of these published techniques to more realistically assess how key aspects of the public health response might impact on the outcomes of a bioterrorist attack. We combine a within-host mathematical model with our spatial back-calculation method to investigate the effects of a number of important response variables. These include how previously reported levels of adherence with taking antibiotics might affect the total outbreak size compared to assuming full adherence. Post-exposure vaccination is also considered, both with and without the use of antibiotics. Further, we investigate a range of delays (2, 4 and 8. days) before interventions are implemented, following the last day of symptomatic onset of some number of observed initial cases (5, 10 and 15). Our analysis confirms that outbreak size is minimised by implementing prophylactic treatment after having estimated the exposed area based on 5 observed cases; however, imperfect (rather than full) adherence with antibiotics results in approximately 15% additional cases. Moreover, of those infected individuals who only partially adhere with a prophylactic course of antibiotics, 86% remain disease free; a result that holds for scenarios in which infected individuals inhale much higher doses than considered here. Increasing logistical delays have a particularly detrimental effect on lives saved with an optimal strategy of early identification and analysis. Our analysis shows that it is critical to have systems and processes in place to rapidly identify, geospatially analyse and then swiftly respond to a deliberate anthrax release.