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A sentinel against airborne biological threats such
as anthrax and smallpox, BASIS offers rapid, high-confidence detection of
bioterrorism.
It?s a sunny morning in late June. Tourists and locals throng midtown
Manhattan, near Central Park South. The air carries a mix of aromas Near the park?s entrance, a solitary sentinel That lifesaving sentinel is part of BASIS, the Biological Aerosol Sentry
and Information System. The air-monitoring system illustrates the best
in national laboratory�private enterprise collaboration in the interest
of public safety. Now being deployed in cities across the country, it
was developed through a partnership between Los Alamos and Lawrence Livermore
National Laboratories and a New York manufacturer of air samplers, Rupprecht
and Patashnick Co.
Los Alamos research into air-monitoring systems for detecting dangerous
microorganisms dates back to the Gulf War, when the nation as a whole
became much more aware of the threat of bioterrorism. Led by J. Wiley
Davidson, a talented team of scientists and engineers from D-3 (Strategic
Systems Engineering), D-4 (Technology Modeling and Analysis), and NIS-4
(Space Engineering) began designing an aerosol-biothreat detection system
in the mid-1990s.
Teaming with Livermore brought the system a giant step closer to becoming
a functional technology. The final steps occurred in 1999�2000, with the
recruitment of Rupprecht and Patashnick, an Albany company that manufactures
air samplers for the Environmental Protection Agency. By 2001, BASIS was
being readied for testing, when the tragic events of September 11 drove
its developers into emergency mode. Five months later, they deployed BASIS
during the Winter Olympics in Salt Lake City.
A Sinister Threat Biological weapons, however, are more sinister in that they are self-enlarging,
using their infected hosts to multiply them. Therefore, terrorists could
initiate an attack using miniscule quantities of infectious spores, cells,
or viruses. Detecting these small quantities before their release is very
difficult.
Thus, at this time, the goal of biological antiterrorism—and the
concept behind BASIS—is early and unambiguous release detection,
or "detect to treat." Early detection can save lives—for
example, early treatment of anthrax-infected individuals with antibiotics
is highly successful in preventing mortality. The time course of anthrax
is variable—symptoms may begin to appear at anytime from one to
seven days after infection. But the overall recommendation from the Centers
for Disease Control and Prevention is emphatic: "Early antibiotic
treatment is essential—delay lessens chances for survival." An Integrated System A suction pump in the samplers draws outside air through filters with
microscopic pores, which capture tiny particles including bacteria and
viruses. Two parallel particle-capture systems operate simultaneously.
One, called the holder, typically collects particles for four hours. The
other, called a magazine, contains several filters, each of which collects
for one hour.
So, for example, the air in a city center during the morning rush hour
(6–10 a.m.) would be sampled by five filters per air sampler, a
holder filter that had collected for the entire four-hour period and four
magazine filters, each having collected for one hour. Only if a holder
filter later tests positive for a biothreat organism are its associated
magazine filters also tested. This enables hourly biothreat detection
while minimizing the number of biochemical assays performed. Software The software allows operators to remotely
monitor and adjust all critical parameters for either a single sampler
or an entire deployed group. For the sake of rapid recognition, these
parameters are displayed both numerically and graphically. Using both
visual and auditory alarms, the control computers notify BASIS operators
of any changes in sampler function that would seriously impair sample
collection. [figure: air-sampler
parameters]
There is also the issue of security. Although each sampler is locked
and password-protected, it is clearly imperative that no tampering occur.
To ensure tamper-free operation, each sampler sends a "state-of-health"
message to the control computers at 10-second intervals.
Another daunting task handled faultlessly by
BASIS software is tracking the fate of filters. Just before the end
of
a holder filter's collection period, the BASIS operator deploys
a replenishment team, which delivers a fresh holder and magazine to
the
sampler and collects exposed filters. All filters are barcoded so that
they can be tracked from deployment through analysis. [figure:
barcoded filters]
Fresh and retrieved filters are contained within sealed chain-of-custody
bags to ensure that filters are accounted for at all times during transit.
The software's database stores the history of every filter deployed
over the course of a given surveillance campaign (and from previous campaigns
as well). Mobile Biochemistry A "hit" (positive test) on a holder filter mandates testing
of its associated magazine filters, both to confirm the hit and to narrow
the time of exposure. Should this confirmation ensue, followup testing
is conducted on the target DNA. These more sophisticated assays can sometimes
identify the strain of the organism present and also identify—through
DNA sequencing—whether the organism has been altered by genetic
engineering to make it more virulent or resistant to drugs.
A primary hit requires only eight hours from sample collection through
PCR analysis. The followup testing can be done in a few additional hours,
making it possible to diagnose and determine the time and place of a bioterrorist
attack within twelve hours of the release. In turn, this expeditious assessment
makes it much more probable that exposed individuals can be alerted and
treated before the onset of symptoms—in time to save lives. Thwarting, Not Inciting, Terror That the system must be infallible may be less obvious. Any technology
that reports a terrorist incident where none exists may induce the very
panic and social disruption it is intended to thwart. Therefore, the rate
of false-positive alarms must be zero or very nearly so. During deployment
in 2002, for about 100,000 screened filters, the rate of false positives
in primary assays was less than 0.005 percent—that is, less than
one false positive per 20,000 assays. Considering that primary hits on
holder filters must be verified both by magazine-filter testing and secondary
testing, these numbers should reassure Americans that their air quality
is being monitored by a discriminating sentinel that is unlikely to set
off false alarms. Bio-Watch and Beyond And while BASIS extends its guard over the nation's airways, the
BASIS team continues its research and development work, seeking to improve
all aspects of system performance. Several new versions of BASIS software
have already been implemented, and developers are constantly exploring
ways to miniaturize samplers and improve their performance, particularly
in smog-laden urban environments. Lightweight, unobtrusive samplers with
higher airflow have already been designed and may soon be commonplace
in our cities. |
Rupprecht and Patashnick air sampler.
BASIS air sampler deployed during the Winter Olympic Games in Salt Lake City.
BASIS air samplers have been recently deployed in New York City.
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