Fears about the use of bio-terrorist weapons abound, both on the war and home fronts. John Palisano, a professor of biology at the University of the South in Sewanee, Tenn., teaches a course on bio-terrorism, and also tries to educate everyone on what they need to know about the four agents most likely to be used -- anthrax, smallpox, plague, and botulism.
I. Anthrax
'In my opinion this is probably the most dangerous agent because it can be weaponized easily with very little expense. However, the weapons grade anthrax that was released in October 2001 is more difficult to obtain, but as we saw very effective and difficult to clean up," says Palisano. 'I think that it is more dangerous than smallpox, even though it is not contagious, because it is difficult to make the differential diagnosis and to institute treatment with antibiotics early enough to be effective therapy. It is difficult to make the differential diagnosis because the early symptoms of inhalation anthrax are similar to most viral, respiratory illnesses."
He reports the following are three presentations for anthrax:
-- Cutaneous occurs when lesions, like cuts, on the skin are infected with the bacterium, Bacillus anthracis. 'The infection begins with an itchy bump that resembles an insect bite. However, within a day or two the lesion becomes a fluid-filled ulcer, and a black scab forms in the center of the ulcer," he says. 'If left untreated the mortality rate is around twenty percent. With early antibiotic therapy, death is a rare outcome."
-- Gastrointestinal anthrax is usually obtained by eating contaminated food and has two presentations. 'The most common form resembles food poisoning; the initial symptoms are nausea, loss of appetite, vomiting, and fever. These symptoms are followed by abdominal pain, vomiting of blood, and severe diarrhea," says Palisano. 'A less common form presents with sore throat, fever, trouble swallowing, and ulcers in the mouth and back of the throat. If left untreated, the mortality rate from gastrointestinal anthrax is 50 to 70 percent."
-- Inhalation anthrax is the most dangerous, with early symptoms resembling a flu-like illness. 'The symptoms include fever, headache, chills, nausea, vomiting, muscle aches, and fatigue. Later during the illness, the patient experiences high fever, pulmonary edema, difficult breathing, and low blood pressure (shock). Antibiotic treatment must be initiated within two days of exposure to be effective," he says. 'The mortality rate is close to 100 percent without appropriate treatment."
Bacillus anthracis is ubiquitous, and readily available to anyone who knows how to isolate it, according to Palisano. It is not easily transferred to humans since the incidence is low. It is most commonly found in people who shear sheep or tan the hides of cattle and presents as cutaneous infection. He also points out that some people develop gastrointestinal anthrax from eating contaminated meat.
'Most investigators think that the sophistication seen in the anthrax release of October 2001 is difficult to achieve. Once the endospores settle to the ground, they probably won"¢"¢t present any greater threat than naturally occurring endospores," Palisano says.
'It is more difficult to predict the effect and ability of the endospores to cause disease if they get into a building"¢"¢s ventilation system. Successful aerosolization of the endospores is very sensitive to the size of the particles "¢V milling the endospores to make them easy to disperse, and meteorological conditions."
II. Smallpox
'Smallpox isn"¢"¢t readily available. Until several months ago, it was thought that only Russia and the U.S. had smallpox stored at one location in each country. An unconfirmed report suggests that France may not have destroyed their repository of smallpox even though they claim that they did destroy their smallpox stocks. It is not widely known who has some of the virus, either obtained by thief or not destroying stocks as reported," says Palisano.
While smallpox is communicable, he points out that a person has to be within six feet of an infected patient to contract it. It presents in the following manner:
-- Macular lesions appear within 14 to 16 days of exposure to the virus, following a 12-day incubation period -- The two to four-day early stage of the illness is the first clinical sign of infection "¢V presenting with fever and a general feeling of malaise. -- This is quickly followed by headache, backache, and a fever that can go as high as 40 to 41 degrees Celsius. Rigor, vomiting, delirium, and an erythematous rash can also present at this time. It is not likely that many people will approach someone with smallpox lesions because the lesions are frightening.
'In a study by Rao, he recognized four clinical varieties on smallpox, each with distinctly different morbidity and mortality rates. The most aggressive presentation had a mortality rate close to 100 percent in his study while the fatality rate in unvaccinated who presented with ordinary variety was around 30 percent and dropped to three percent in those who were vaccinated," he says. 'It is thought that those people who were vaccinated before 1972 might have some residual immunity and not get a severe case of smallpox, if they are exposed to smallpox. The only form of protection is vaccination, and it must be administered within two to four days of exposure to be effective."
Since humans are the only animal that contracts smallpox, it will not persist long if all people exposed to smallpox and their contacts and quickly quarantined and vaccinated, according to Palisano. 'While smallpox is reported to be difficult to process for aero-solization, it is thought to be relatively stable in aerosol form when the weather conditions are dry and cool."
III. Plague (caused by Yersinia pestis)
'It is relatively widespread and stored in many labs worldwide. While it can be weaponized, it takes a great deal of technological knowledge, like the weaponization of anthrax," he says. 'The microorganism is sensitive to sunlight and heat.
The disease presents in two forms. The most common, naturally occurring presentation is cutaneous and obtained from a fleabite. The bacterium then spreads to the nearest lymph nodes where it causes swelling of nodes called buboes, hence the name bubonic plague.
'If the microorganism travels from the lymph nodes to the lungs or is inhaled "¢V from a bio-terrorist attack, it causes pneumonia," Palisano says. 'Unlike bubonic plague which can be treated effectively with antibiotics, the mortality rate is around 50 percent for pneumonic plague if treated, and near 100 percent if it goes untreated."
He reports that the incubation period can range from one to six days for the inhalation form, and the early symptoms of plague first appear two to four days after exposure to the bacterium.
The initial symptoms are similar to many respiratory illnesses, making the diagnosis difficult. If it is untreated, death can follow within two days of presentation with pneumonia.
'In cases of bubonic plague, the first symptoms do not present for two to eight days after exposure and consist of sudden fever, chills and weakness. These symptoms are followed by swollen and painful lymph nodes," he says. 'Without the appropriate treatment, the patient goes into respiratory failure, or shock. Death may follow within two to four days after the early symptoms."
Palisano does not believe it poses much of a threat once it has fallen to the ground for two reasons. First, it is very susceptible to sunlight and heat inactivation. Secondly, the bacterium has been reported on every continent, except Australia, and only 1700 cases are reported annually.
IV. Botulism
'Like anthrax and plague, the microorganism that produces the botulism toxin is found worldwide so it is not difficult to obtain the toxin. While it is one of the most poisonous substances known to science, it is difficult to stabilize the toxin which is necessary to make it easy to disseminate as an aerosol," he says. 'It is more likely to be used to contaminate food, which is the manner that most humans are contract with the toxin.
Because it is not easy to stabilize and it deteriorates in bright sunlight, Palisano believes it probably would not persist in the environment. He also reports that botulism toxin is inactivated by heating food to 185 degrees Fahrenheit for five minutes.
'The toxin acts by binding to neuromuscular junctions "¢V where nerve endings join muscles "¢V and causes paralysis," he says.
Palisano reports that the first symptoms of botulism toxin poisoning can occur within 12 to 36 hours after eating contaminated food. Those symptoms include double vision, blurred vision, drooping eyelids, slurred speech, dry mouth, and muscle weakness. If untreated, the paralysis moves from head and neck muscles down the body "¢V causing death when it leads to respiratory failure.
While there has been an experimental vaccine in development for 30 years, the treatment of choice is to give an antitoxin "¢V antibody to botulism toxin "¢V raised in horse.
'The antitoxin prevents any toxin in the blood from binding to nerve endings. However, it cannot reverse any paralysis that has occurred," he says. 'If the disease is in a late stage before treatment is initiated, the patient may have to be placed on a ventilator to assist breathing. Paralysis if treated will improve, but it may take months of extended care.
'The best advice I can offer for people is to go about their daily life and keep their eyes and ears open. Report anything that you think is unusual, suspicious, or out of place to the proper authorities. Living in fear will not benefit anyone, and it will add to distress and confusion should a bio-terrorist attack occur. If a bio-terrorist attack occurs, follow the advice given by first responders and act in an intelligent manner. Be prepared for any eventuality so that you are not taken by surprise."
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