NOVA Online | Bioterror | Ask the Expert Responses, 11/16/01

Ask the Expert
Responses from Dr. Jonathan Tucker
Set 2
Posted November 16, 2001
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Q: Examination of sites are reported to have "trace" amounts of anthrax. If not decontaminated, how long will the anthrax remain active? What are the possibilities of "false positives" at these sites, and how is the baseline and calibration of the tests used established?

A: If traces of anthrax spores are not killed with bleach or exposure to ultraviolet radiation, they can persist in a building for months or even years. Because the spores tend to adhere tightly to surfaces, however, it is extremely unlikely that trace amounts could be reaerosolized to cause inhalation anthrax. Rapid preliminary tests for anthrax can result in false-positives, but follow-up tests (involving culturing the anthrax bacteria) are highly reliable.

Q: In the 1950s and 1960s United States government scientists released bacteria over U.S. cities. Even though the scientists claimed that the viruses were harmless, doctors have records proving that many citizens became ill as a result. Why hasn't the U.S. government made reparations to the citizens, and how can we be certain that our own government has not and will not again dump biological weapons on anyone.

A: The microbial agents released over U.S. cities during the biowarfare experiments of the 1950s and 1960s were "simulant" bacteria such as Serratia marescens, which do not harm healthy people but occasionally cause illness in people with an impaired immune system. Although a cluster of cases of S. marescens infection was reported in hospital patients following a biowarfare simulant test in San Francisco, the evidence for a cause-and-effect relationship was not clear-cut, and the U.S. government denied responsibility. Testing of biowarfare simulants over populated areas ended in the 1960s.

Q: I understand that cowpox, which is much less virulent than smallpox, confers immunity from smallpox. Considering the fact that there is not enough smallpox vaccine to go around, would it be feasible, in an informed consent scenario, to be prophylactically infected with cowpox? It would have the virtue of decreasing the number of people who would require the vaccine if the need arose.

A: Cowpox virus was the original smallpox vaccine developed by Edward Jenner in 1796 [see Making Vaccines]. Since then, cowpox has been replaced as the active ingredient of smallpox vaccine by a different but related virus known as "vaccinia." Although vaccinia produces a harmless, localized infection in most people, it can protect against the far more virulent disease caused by the smallpox virus.

Q: Do the anthrax spores germinate when they come in contact with water, and is it safe to flush these spores down the drain as is recommended when you are exposed?

A: Anthrax spores will only germinate in a moist, nutrient-rich environment such as the interior of the human lung. Anthrax is not naturally transmitted through water, and even if terrorists were to dump anthrax spores in an urban reservoir, the spores would be killed by chlorination during the water treatment process.

Q: My question is how effective would it be for the terrorists to disperse any biological or chemical weapons from an airplane? I have heard that it can actually break down the pathogen and make it essentially ineffective. Thank you for your time.

A: Reports that some of the September 11^th terrorists were interested in crop dusters have raised concerns that the perpetrators were planning to use such aircraft to spray biological agents over populated areas. Standard crop-dusting equipment, however, would not be suitable for this purpose without extensive modification. The reason is that a crop duster is designed to spread a pesticide or fertilizer over a single field of crops, while minimizing drift of the chemical over adjacent fields. In contrast, someone seeking to disseminate a biological agent over a large target area would want to maximize the drift of the agent downwind.

Q: How likely is it that an agent like smallpox, if used, will spread back to the country of origin and the world? Do terrorists have to fear their own weapons?

A: Since smallpox (unlike anthrax) is contagious from person to person, it is not a "targetable" weapon. Thus, an attacking country would run the risk that the resulting epidemic might spread uncontrollably and eventually affect the attacker's own population. Terrorists handling smallpox virus would also be at great risk of infection themselves unless they were vaccinated, although some fanatics might be prepared to die in carrying out an attack.

Q: Is it true that you can sterilize your mail by putting it in the microwave for 30 seconds? Will that help if my envelope was contaminated in the sorter?

A: Microwaving letters is not an effective way of sterilizing mail. In fact, such treatment could actually rupture an envelope containing anthrax spores and contaminate the interior of the oven. Instead, any lettter that appears suspicious should be sealed in a plastic bag and reported to the local health authorities.

Q: I am currently a junior at Skutt Catholic College Preparatory High School in Omaha, Nebraska. I am doing an independent research study in my Accelerated Physics class. I am trying to prove that the use of mass spectrometry/optics will be a crucial detection mechanism in the war against biochemical warfare and terrorism.

What are your thoughts on this subject? Any related information would be greatly appreciated. Thank you.

A: Mass spectrometry is a useful analytical technique for identifying chemical warfare agents, as well as certain biological toxins (nonliving poisons produced by living organisms, such as botulinum toxin or ricin).

Q: I was born in 1957. Weren't all the children in the U.S. immunized against smallpox at that time? Would people who were immunized as children stand a better chance of fighting off an exposure to smallpox now? Please explain if different strains of smallpox are at issue and whether the vaccination definitely "wears off" after a number of years. Thank you.

A: Vaccination against smallpox was mandatory for U.S. children before school entry until 1972. People who were vaccinated once in childhood may retain some residual immunity that would probably not protect them from infection entirely but would make the disease somewhat milder. Those who were vaccinated two or more times (such as military recruits or travelers to smallpox-endemic countries in the 1960s or 1970s) should have a significantly higher level of immunity. Smallpox vaccine protects against all known strains of the virus.

Q: I know anthrax spores can live 100-odd years. But is there any way for us to tell whether anthrax discovered on a post office sorting machine tomorrow is a new incident (i.e., from a recent mailing, not from an older mailing that wasn't discovered at that time)? Is there any way to tell how long anthrax spores have been sitting on a surface, for example?

A: It is impossible to distinguish between anthrax spores deposited on surfaces a few days apart. If the spores had been deposited on letter-sorting equipment years earlier, it is likely that they would have caused detectable cases of disease among postal workers.

Q: Do you believe our nation's agriculture may be threatened under the auspices of economic sabotoge? If so, do you believe additional research may benefit this as it has done with anthrax and botulism?

A: The U.S. Department of Agriculture is very concerned about the possibility of "agroterrorism" as a means of economic warfare against the United States. Indeed, a single outbreak of foot-and-mouth disease could shut down the nation's entire beef exporting industry, inflicting severe economic damage on ranchers and meat packers. Accordingly, further resarch on vaccines and other control strategies for livestock disease is warranted.

Q: What does it mean to "weaponize" a germ?

A: The "weaponization" of a microbial pathogen or toxin involves several dimensions. These include: (a) rendering the agent resistant to standard antibiotic drugs; (b) freeze-drying and milling the agent into an extremely fine powder, consisting of particles tiny enough to become readily airborne and inhaled into the victims' lungs to cause infection; (c) stabilizing the agent so that it will remain infectious for a longer period after release; and (d) treating the powder with chemical additives that absorb moisture and reduce clumping, so as to facilitate aerosolization.

Q: Why can't dogs sniff out bioweapons like they do drugs?

A: If a dried biological warfare agent is transported in a sealed container, it will not give off any odor or other "signature" that could be detected by dogs or by some mechanical detection device.

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