The WMD Notebook: Staphylococcal Enterotoxin B

Prior to the fall of 2001, very few individuals in the Unites States, outside of the Centers for Disease Control (CDC) or the military, gave much thought to the possibility of a biological attack on this country. The events of September 11, 2001 and the anthrax attacks through the postal service in October of 2001 changed the perceptions of most Americans. While anthrax, smallpox and other biological agents have been media buzzwords for the past seven years, many other agents remain unknown to the general public. One of these unknowns is Staphylococcal Enterotoxin B or SEB.

The History of Staphylococcal Enterotoxin B
SEB was one of the many agents studied by the United States Army for use in a biological weapons attack during the Cold War. SEB was weaponized during the 1960's and stockpiled until 1969 as Agent PG. It remained as part of the biological arsenal while the United States maintained an offensive biological capability until the Biological Weapons Conventions of 1972. Like other biological weapons, SEB was developed due to the extremely small amounts needed to incapacitate its intended victims. It is listed as a Category B agent by the CDC.

SEB may be either inhaled through the lungs or ingested through the intestinal tract. Both routes of exposure yield different results. For inhalation, the dose required to kill 50 percent of a target population (LD50) is only 0.0014 grams. The dose required to incapacitate 50 percent of a target population (ID50) is even less at 0.000028 grams (Ellison, 2008). With numbers such as these, it is easy to see why biological weapons have been identified as the "poor man's atomic bomb".

Like all toxins, SEB is normally found in nature. It is not a man-made weapon such as a nerve or blister agent. Very little information exists as to how or where SEB occurs in nature. (Ulrich, 1997) Infections have been found in rodents, sheep and cattle. It has been the cause of numerous outbreaks of food poisoning, but the exact numbers cannot be known. Many incidents of food poisoning go either unreported or are simply written off as a case of the "stomach flu". Many people do not realize they have contracted food poisoning and therefore misdiagnose themselves. This makes tracking cases of SEB outside of the laboratory environment extremely difficult.

SEB has not been confirmed as having been used in any act of bioterrorism. Just because it has not, does not mean it will not. While American stockpiles have either been destroyed or held under rather tight security, the same cannot be said about stockpiles held by the former Soviet Union. The United States has been assisting the former Soviet states, but the issue is still in doubt.

SEB is the second most common cause of food poisoning, making it quite common outside of the laboratory. Some knowledge and rudimentary laboratory equipment could produce a weaker strain of SEB. This weaker strain may not be as lethal or incapacitating as weapons grade SEB, but the results (straining local emergency medical services (EMS) and public health agencies in addition to instilling fear into the general public) will still be achieved.

The bacteria can be grown in a growth medium or agar in a Petri dish. The colonies will continue to replicate until thousands of them exist. The bacteria can then be freeze dried to form a spore. The spores remain relatively stable for years and are extremely difficult to detect for first responders in the field.

Signs & Symptoms of SEB
The primary routes for SEB to invade the body are inhalation and ingestion. Inhalation will result in a faster onset of symptoms, but they will be somewhat different than the signs and symptoms demonstrated by ingestion.

Victims will become symptomatic approximately one to six hours after inhaling SEB. As with all chemical and biological weapons, the wide time frame depends upon the physical condition of the victim, dose exposed to, grade of the agent used (weapons grade or home grown) and the time that the victim was exposed. As with other medical emergencies such as the common flu, the older and younger populations in addition to those with depressed immune systems (such as organ transplant recipients and those who are HIV positive) are more susceptible to the effects of the agent. Only one to two percent of all SEB cases would result in fatalities.

Effects of SEB inhalations include muscle pain, headache, chills, a non-productive cough and fever. Nausea, vomiting and diarrhea are also possible, but these symptoms are more likely to occur in victims that have ingested SEB. The fever may go as high as 106 degrees F and last up to five days. A fever that is that high and lasts that long could have severe repercussions on the central nervous system. The cough may last as long as four weeks. Difficulty breathing and chest pain are also possible in more severe cases. It can easily be seen how the above symptoms can easily be misdiagnosed as the common flu. The majority of patient will recover in one to two weeks.

Effects of SEB ingestion include vomiting, retching, abdominal cramping and diarrhea. In severe cases, the diarrhea may become watery and explosive. Some patient may also present with headache, dizziness and overall weakness. Fever is generally restricted to inhalation exposure only. Complications due to dehydration caused by severe diarrhea may also be seen. Recovery from SEB ingestion is much faster that SEB inhalation. Most patients will recover within one day. It can easily be seen how a biological attack with SEB could easily be dismissed as a simple case of "bad meat" or food poisoning.

Attack Strategy
Assuming SEB could be attained or produced by a terrorist organization, how could it be employed against an unsuspecting population? Contaminating a food or water supply would be an excellent method to infect a segment of the population through ingested SEB. A small, localized attack would be more effective that a large scale attack against a major segment of the food supply, such as a water reservoir. An attack against a water reservoir would be pointless even though SEB is not affected by the chlorine used for purification in municipal water supply systems. A rather large amount would be needed due to the millions of gallons of water present. If enough biological agent was not introduced into the water supply, it may be diluted to the point where it would be ineffective and not cause any casualties or fatalities at all.

The most effective method of attack utilizing ingested SEB would be through a small concentrated attack against a small segment of the population. A dedicated group of terrorists with a small quantity of SEB could contaminate a series of salad bars or buffet-style restaurants. With a little practice, the contamination could take place without anyone noticing the act taking place. If a group didn't want to run the risk of being detected by contaminating salad bars or buffet lines, the contamination could take place at the restaurant tables as well where it would be even more difficult to notice the act in progress. SEB could be introduced to salt and pepper shakers, sugar jars, coffee creamer or any other condiments that may be on the table.

With a little more planning, the contamination could take place before the food makes it to the serving line. If there is one thing that is evident since the attacks of 9/11, it is that terrorists are patient and willing to plan their attacks out to the last, minute detail. A terrorist cell could place sleeper agents into any number of restaurants as cooks, dishwashers, wait staff, etc. Once the order is given and the SEB is distributed to the cell members, it would not be difficult for the agents to poison the food in any number of restaurants.

Does the idea of contaminating restaurants seem too far fetched? Is it something that could only happen overseas and not in our own back yard? The answer is a resounding no! A biological attack just as described above has occurred. The attack did not occur in the Middle East or Europe, but in our own back yard. The Rajneesh Cult in Dalles, OR, sought to influence a zoning change that was on the ballot of a local election. Several members of the cult used a similar biological agent, salmonella typhimurium, to poison several local salad bars. The result was almost 800 cases of "food poisoning" being reported to local hospital emergency rooms and doctor's offices.

How was the poisoning discovered? A watchful official at the department of public health (state, federal) was able to connect the dots as more and more cases were reported that this "outbreak" was more than just a simple case of food poisoning. Several members of the cult also came forward and contacted the local District Attorney's office after they became concerned that the cult was becoming entirely too radical for their tastes. We cannot depend on being as lucky again. The Rajneesh cult only sought to make people sick enough so they couldn't vote of the scheduling rezoning issue. International terrorist groups have sworn to eliminate the "Great Satan" at all costs. The price of peace is indeed eternal vigilance.

The other means of using SEB in an attack is to introduce the spores into the atmosphere in order to produce an inhalation hazard. The attack could be as simple as introducing the spores into the atmosphere and letting natural air currents carry them downwind. This method is amateurish at best and not very effective. Terrorists have already shown the ability of using aircraft in their attacks, going back into the 1970's when the idea was first broached about using small aircraft as suicide vehicles against Israeli tanks. If it is possible to master the flight characteristics of large aircraft such as Boeing 757's, it is much easier to learn to fly a small aircraft such as a crop duster.

Terrorist sleeper agents could gain practice and credibility by operating legitimate crop dusting operations. This could be done below the radar if operatives could be found that are sympathetic to their cause and not of Middle Eastern descent. SEB could be placed into the crop dusting apparatus and sprayed over a large geographic area. While a high profile target such as the Super Bowl, World Series or Daytona 500 would make an ideal target, they would be more difficult to hit due to the enhanced security measures (including Federal Aviation Administration enforced No Fly Zones) now being used for incidents of national significance.

It would be much easier for the terrorist cell to fly an aircraft (or several) over a large urban or suburban area. Rural areas could be ruled out due to the decreased population present. As a society, we have become accustomed to having small aircraft and helicopters overhead all the time during the day. A pilot, dispersing product in a straight line (as opposed to a "search pattern") could poison thousands of people without drawing attention to the plane at all. SEB in its natural form is a white powder. In an attack described above, an attack wouldn't even be noticed. Even if it was applied in a heavy handed fashion, it could easily be mistaken for pollen if the attack was conducted at the right time of year.

Military tests have proven that an agent sprayed from a single aircraft could cover an area twice the size of Los Angeles. (Hanson, 2006) A test conducted by the military in the 1950's off of San Francisco also proved that an agent could be sprayed from a ship off shore and use the prevailing winds to carry the agent ashore. An attack such as this could be particularly difficult to detect or prevent if the vessel in question remained in international waters.

Attack Aftermath
What could we expect in the aftermath of an attack utilizing SEB? Large outbreaks of the flu already tax understaffed EMS systems and hospital emergency departments during a particularly active flu season. If there is a plus side here, it is that the flu season can last for weeks of months. In the event of an SEB attack, EMS providers (including fire departments who respond as medical first responders or EMTs) and hospital emergency departments would be overwhelmed, particularly in the case of SEB exposure through inhalation.

There could most certainly be a public panic, especially if a terrorist organization claimed responsibility. People with the slightest of symptoms, or those with psychosomatic symptoms would be calling fire departments and EMS providers for treatment or self-transporting to local hospitals. Local emergency departments are already reporting waiting times of several hours for some patients to be seen. This would only grow much worse after an SEB attack. Law enforcement may have to be called in order to prevent chaos at local hospitals. Patients would have to be considered contaminated in order to not cross contaminate the hospitals as occurred after the Sarin gas attack in Tokyo in 1995. Most hospitals lack the facilities, personnel and training in order to decontaminate large numbers of people. The task of mass decontamination would fall to the local fire department, most likely the Hazardous Materials Team. With the fire department experiencing an increased call volume due to the aftermath of the attack, it could scarcely afford to have several companies deployed to each hospital in order to decontaminate hundreds if not thousands of people.

Triage would also be a significant issue. For cases of severe respiratory exposure, mechanical ventilation may be required to assist a victim's breathing. The number of ventilators on hand is based on the normal, every day need, not the possibility of a terrorist attack. In short, dozens of ventilators are not kept on stand-by,"just in case". Who would get access to the ventilators? Would existing patients be removed from them in order to save people injured during the terrorist attack? Who would make the call? It would undoubtedly create an ethical dilemma for medical practitioners.

Case Study: Accidental Exposure
Sidell draws upon a previously unpublished report that gives us some insight into what a possible attack by SEB would be like. Nine laboratory workers were accidentally exposed to SEB through inhalation. The patients became ill within three to hour hours post exposure and were affected for three to four days. Three of the patients became seriously ill. All nine patients suffered from fever and chills with temperatures reaching as high as 106 degrees F.

All of the affected workers were admitted to the hospital with varying rates of respiratory difficulties. Seven workers complained of moderate chest pain, but there were no cardiac affects due to the exposure. Eight of the workers complained of headache, with some lasting as long as three days. Most workers complained of abdominal pains, nausea and vomiting of varying degrees, but none complained of diarrhea. Routine supportive care was all that was required for the nine exposed individuals. This is all that can be done as there is no vaccine or antidote available for SEB. Treatment can be further complicated by excessive exposure resulting in severe respiratory distress requiring assistance by mechanical ventilators. Concerns over fluid replacement for losses caused by diarrhea would also have to be addressed.

Details of the exposure, such as how the exposure happened, what the total exposure was and the strength of the strain being used were not made available. It would reasonable to assume that the exposure was relatively minor due to personal protective equipment being worn by the workers and built in safeguards such as ventilation filters designed into the laboratory itself. Since it was a medical research laboratory, it could be assumed that that strain was weapons grade or fairly close. What does this tell us about a possible attack?

Nine people required hospitalization after a brief exposure. What if this was extrapolated to be 90, 900 or 9,000? How many jurisdictions could handle a sudden surge of 900 people requiring hospitalization? Local hospitals would quickly be overrun, not counting the usual emergencies that they see every day. Patients would have to be transported to surrounding hospitals, further straining an already overtaxed EMS system. This does not take into account the possible economic impact.

Inhalation SEB may take as long as two weeks to partially recover from, with another two weeks of persistent cough for a possible total recovery time of four weeks. If several hundred people are forced to stay home from work for four weeks, this will have a ripple effect across the jurisdiction in question, particularly is large numbers of emergency services (police, fire and EMS) workers are involved. Overtime will have to be paid to cover first responders who are out sick. This will tax already tight budgets. Businesses may be forced to close because they have no employees available to come to work. If health care workers (doctors, nurses, etc.) fall ill due to cross contamination, who will be available to care for the sick public? Hundreds of thousands of healthy people may be forced to stay home from work to care for injured family members, friends or loved ones.

The main goal of SEB is to incapacitate, not kill, as the mortality rate is only one to two percent. By incapacitating large numbers or people, even more resources are required to care for the sick ones. The principle is similar to the use of land mines on the battlefield. A soldier who has been killed can be left and buried at a later date. A soldier who has been injured required two to four other soldiers to evacuate the injured soldier to the rear areas. It is the requirement for the additional resources that taxes the system.

Conclusion
SEB does not have the name recognition of anthrax, plague or smallpox but it is dangerous nonetheless. It does not have the mortality rate of a viral hemorrhagic fever or the hideous scarring of smallpox. It does however, have the ability to create chaos in the general public and overextend the capabilities of local First Responders. Its ability to cause short term economic difficulties makes it a viable agent for use in biological attack by a terrorist organization.


MARK SCHMITT, a Firehouse.com Contributing Editor, is a firefighter with the Greensboro, NC, Fire Department and serves on their hazmat team. A 16-year veteran of the fire service, Mark started with the Rivera Beach Volunteer Fire Company in Maryland and holds an Associate of Arts Degree in Fire Protection Technology from Guilford Technical Community College and a Bachelor of Science Degree in Fire Safety Engineering Technology from the University of North Carolina at Charlotte. Mark is a member of North Carolina's Hazardous Materials Regional Response Team 5 (RRT 5) and in an instructor in various topics related to hazmat and fire service operations. To read Larry's complete biography and view his archived articles, click here.

Loading