Biosurveillance needs or requirements currently differ with each user and application, in part because existing biodetection systems are limited by the following:
- the need to cultivate pathogens prior to detection;
- a requirement for sampling and direct contact between the sensor and pathogen;
- the non-specificity of molecular recognition elements;
- a requirement to identify trace levels of pathogen in very large sample volumes; and
- the chemical and biological complexity of the background environment.
Thus, no one technology currently satisfies the disparate operation needs of public health, epidemiology, environmental monitoring, first responders, clinicians and doctors, the military, intelligence, law enforcement or forensic users. An idealized system that would satisfy a broad spectrum of biosurveillance needs is embodied in the fictional "Tricorder" popularized in the science fiction series "Star Trek." Intrinsic features of the Tricorder that make it such an attractive concept for biosurveillance are the fact that it
- operates remotely and never contacts a sample directly;
- detects multiple analyses simultaneously;
- diagnoses the situation;
- reports with perfect confidence; and
- provides results instantaneously,
- identifys new signatures for life versus not-life.
What is needed are new approaches to biodetection that do not suffer from the limitations of existing biodetection methods, yet approach the performance features of the fictional Tricorder.
The Tricorder is instantaneous, diagnostic and perfectly accurate. Instantaneous answers are always preferred, but the user's requirement for analysis speed are tempered and balanced by the confidence associated with the result. That is, different users require different types of information with differing levels of confidence. A first responder needs to know immediately whether there is a "biological" or "nonbiological" entity associated with a scene simply to ensure the safety of the first responder. Such information is enough to warrant action. After securing a scene and within a 15-minute time frame, the first responder would like to know whether the entity is of biological concern or not. Similar concepts and staged information applies to other biosurveillance scenarios; the sooner a high quality result is in hand, the sooner action can be taken.
There are currently 20-30 biological agents of concern as weapons. Hundreds more micro-organisms are pathogenic, causing disease and death, and are routinely monitored by various agencies, including the USDA, EPA and CDC. Any and all of them could be agents of a terrorist attack. Thus, the diagnostic element of the fictional Tricorder should be able to distinguish between and/or identify tens to hundreds of different pathogens.
The cost of a detection device or system is in direct proportion to the intended use and the need for additional reagents, which is a logistical burden. After the anthrax release in October 2001, many fire departments and first responder units purchased tens to hundreds of rapid cycler instruments at $55K apiece, and then spent $5 to $10 per test for each of the agents of interest. These costs were ultimately unacceptable to the community. Biosurveillance entails repeated sampling and analysis, such that the reagent costs are typically more onerous than the equipment cost. First responders would be comfortable with a Tricorder-like device that costs $10-$10K per copy but had no wet chemistry or reagents associated with it. A network of distributed systems for buildings (HVAC) or municipalities (water monitoring) and other high- value targets would likely be acceptable at $250K.
Physics and New Directions.
The fictional Tricorder for biosurveillance is not unlike a standard Geiger counter or similar device for detecting and characterizing radioactive contamination. Detecting a biological contaminant in the environment is also not unlike detecting nuclear fallout in the ocean. Searching for a needle in a haystack; inferring the presence of a contaminant from other physical or chemical properties; measuring at a distance; de-convolving complex data; and identifying and diagnosing specifically in a complex and noisy background are the challenges of biosurveillance. They are the types of challenges previously mastered by physicists in a different domain, and hence physicists can be of tremendous value in solving this challenge in the following areas:
- identifying physical signatures associated with man-made production and/or dissemination of biologicals;
- developing new imaging systems to detect biologicals in environmental samples; and
- filtering complex data and processes to arrive at quantitative, confident and defensible results.