Domestic awareness of biological terrorism has increased significantly since late 2001. The U.S. Centers for Disease Control (CDC) has classified and prioritized bioterrorism agents into Categories A, B and C. The following descriptions of the CDC’s definitions include mention of anthrax, ricin and staphylococcal enterotoxin B (SEB), as technology exists for their detection:
•Category Aagents anthrax, smallpox, plague, botulism, tularemia and viral hemorrhagic fever have high potential for large-scale dissemination and adverse public health impact. Anthrax, an infectious disease caused by spore-forming bacterium, appears in three forms: skin, gastrointestinal and inhalational. Inhalational anthrax causes the most deaths as infection is in the lungs. According to the FDA, all three types are treated with antibiotics.
•Category Bagents ricin, brucellosis, salmonella, glanders, staphylococcal enterotoxin B (SEB), typhus and viral encephalitis have low mortality rates and are fairly easy to disseminate. Ricin, which has no known antidote, takes powder, mist or pellet form and is inhaled, ingested or injected. Ricin prevents human cells from making necessary proteins, causing cell demise and death.
•Category Cagents Hantavirus, drug-resistant tuberculosis and staphylococcal enterotoxin B (SEB) are pathogens (bacterium or virus of disease) that are easy to produce and have high mortality potential, thus making them mass dissemination possibilities. Fast-acting toxin SEB spreads through food, water or aerosol inhalation.
Identifying biological agents
Preparedness for biological warfare incidents is complicated by possible delayed onset of disease, as well as contagious effects. Early and rapid identification of biological warfare agents through use of instrumentation requires a specific and sensitive analytical method that overcomes certain challenges. Ideally, biohazard detection should provide:
• correct, complete results with low false-positives rate;
• rapid analysis, allowing first responders to advise public officials;
• preservation of evidence for lab testing;
• detector stability to withstand climate and weather conditions.
Certain biological agents can be identified through use of a method called immunoassay. Analytical detection or immunoassay is a test method that determines the presence, lack thereof, or the measure of components contained within a controlled sample. Three assay or “dipstick” methods for biological warfare agent identification exist:
Lateral flow immunoassayis a one-step format. Its benefits include ease-of-use, short time-to-result and climate stability. It is limited by general lack of sensitivity, specificity and reproducibility; frequent rate of false positives; and lack of a cartridge reader, sometimes resulting in ambiguous readings.
Polymerase chain reaction, a.k.a. free-solution PCR, is a multi-step, field-based assay. Hand-held units use PCR technology to replicate the DNA structure of bacterial or viral pathogens. PCR’s strengths are high specificity and sensitivity with low false-positive rates. It is limited by expensive instrumentation and assay costs, complex sample preparation, cross-contamination possibilities and longer time-to-results.
A more recent immunoassay method isdynamic surface generation, a technology using highly fluorescent particles to bind, concentrate and isolate the sample, providing high sensitivity with virtually no false positives, as potential interferants are removed from sample solutions. Samples are concentrated pre-analysis through magnetic binding and “washing.” Dynamic surface generation combines the benefits of PCR and lateral flow methods for more rapid analysis, ease of use, specificity, detector stability and especially sensitivity, with fewer false positives.
Importance of technology
A large-scale bioterrorism event would likely result in loss of life, treating the sick, and housing and feeding the displaced. HVAC systems and factory floors within industry and offices are potential targets, as are hospitals, schools, malls and stadiums. A real biological warfare event would significantly affect our most basic expectations: clean food and water, public safety, emergency services and essential goods.
When crucial decisions must be made, such as citizen evacuations, closure of mass transit systems, and alerting first responders, hospitals and municipalities, the cost of false positives in dollars, time and public anxiety is enormous. False-positive readings would potentially kick emergency services into high gear, wasting much time, money and patience.
Fast, reliable, comprehensive information is essential for enabling pivotal decision-making among first responders, law enforcement, government agents and security personnel in the event of an attack. Technology has progressed in countering bioterrorism, offering rapid detection, analysis and identification of biological agents.
SIDEBAR: Some historical acts of bioterrorismâ€¦• World War I: German scientists sought to infect grazing livestock with anthrax and glanders through injections and contamination.
• 1936: During its Manchurian occupation, Japan fatally infected 10,000 citizens, using them as test subjects to determine the lethality of anthrax, cholera, typhoid and plague.
• 1940, WWII: Japan’s Imperial Army spread plague amidst China’s population via distribution of contaminated water and food supplies.
• 1979: An anthrax outbreak in Sverdlovsk, Soviet Union, killed 70 residents and was thought to be a natural outbreak. In 1992, investigators determined that those deaths resulted from the accidental release of inhalation-type aerosol anthrax spores from a local military base.
• 1984: Oregon-based religious cult Bhagwan Shree Rajneesh spread salmonella over local salad bars, intending to disrupt an upcoming election. 750 residents suffered food poisoning.
• 1995: Japan’s Aum Shinrikyo cult released sarin gas in a Tokyo subway, killing 12.