Following the anthrax bioterrorist incidents in 2001, first responders and hazmat teams have investigated ways to respond to such attacks. Unlike explosions or spills, biological attacks generally aren't obvious. The anthrax letters and their white powder were unusual in that hazardous response teams were called out to separate innocent powders and hoaxes from real attacks.

In reality, most bioterrorism acts will probably be covert, with the first indications caught in hospital emergency rooms as the ill start to appear. Thus, with the exception of the powder calls, hoaxes or announced spread, it appears unlikely that firefighters will respond to most biological terrorist attacks. Nevertheless, as we've seen with anthrax, the risks remain real.

The bugs

Of the multitude of microorganisms abounding in the world, relatively few cause disease. Of these, the two main kinds are bacteria and viruses. Generally, bacteria are free-living cells with a cell wall, internal organelles for protein production and a looping strand of DNA that isn't encased in a separate nucleus. They come in different shapes and sizes, but most are small, either round (cocci) or oblong (rods).

Most bacteria are non-pathogenic and make life as we know it possible. However, some cause disease in both animals and humans. Many of these pathogens have been known from the mid-1700s and can be controlled with antibiotics, which prevent cell growth by interfering with bacterial cell wall development, or with DNA or protein replication. Increasingly however, bacterial cells carry antibiotic-resistant genes. Not only can bacteria naturally exchange these genes, laboratory workers can manipulate them, making previously susceptible bacteria resistant.

Viruses, in contrast, are composed of nucleic acids — either DNA or RNA — surrounded by a protein coat. They contain no cell wall or energy producing equipment, so to reproduce they have to hijack living cells. They are smaller than bacteria, and because they have no cell walls or organelles, they are not affected by antibiotics. However, some of the new antiviral drugs are promising. In addition, many viruses are controlled by vaccination programs.

The Centers for Disease Control and Prevention has ranked possible bioterrorism organisms into three categories based on their ability to:

• Be easily disseminated or transmitted person-to-person;
• Cause a high mortality and present a major public health impact;
• Cause panic and social disruption; and
• Require special action of public health preparedness.

These categories, A through C, are those select agents that at the present time are most likely to be used as bioweapons, with the A list containing those most likely to be used: anthrax, plague, smallpox, viral hemorrhagic fevers, tularemia and botulism. Of course, bioterrorists aren't limited to the A list. (For the entire list, see www.bt.cdc.gov.)

Anthrax

Known from antiquity, the anthrax bacillus was associated with disease as early as 1752. In 1877 Robert Koch definitively described its pathology and epidemiology and proved, for the first time, that a given bacteria caused a specific disease.

The causative agent, Bacillus anthracis, doesn't like oxygen and prefers to live in places with a reduced atmosphere. When the going gets tough due to reduced food or air exposure, the agent creates spores, the bacterial equivalent of seeds. These spores form within six to eight hours, resist drying and survive well — they can live in the soil for decades.

The disease is endemic in many parts of the world, causing sporadic outbreaks in cattle, goats, sheep and occasionally horses. The spores invade the body by cutaneous cuts or abrasions, ingestion, or inhalation. They germinate, giving rise to vegetative cells and producing toxins that can kill the host animal.

Depending on the entry route, anthrax causes three types of disease: cutaneous, gastrointestinal and inhalation. In cutaneous anthrax, the spores enter via a cut or abrasion, forming a dark, coal-colored scab at the site. (Anthrax is the Greek word for coal.) Gastrointestinal anthrax, which is rare in humans, occurs when people eat infected and undercooked meat.

Inhalation anthrax, the most serious, occurs when spores are inhaled. They lodge in the lungs, germinate into the vegetative rods, and quickly invade the blood stream. In the 17th and 18th centuries, inhalation anthrax was known as woolsorters' disease, spread by spores clinging to hides, furs and wool, infecting those who handled hides and their by-products.

To control anthrax, we need to control the development, dissemination and exposure to spores, for the disease is spread only through the spores. Because the vegetative cells aren't infective, the disease isn't contagious, and because the infective dose appears to be 10,000 to 80,000 inhaled spores, the disease is not particularity infectious either. (In contrast, 10-12 tularemia cells can cause disease.) To control the spread of spores, which the organism creates when the vegetative cells are exposed to the air, infected animal carcasses are burned or buried in lime on the spot.

Its ability to form spores makes anthrax a good bioweapon. For example, once loaded in a delivery device, such as a bomb, the organism stays alive over long periods. Spores also stand up well to rough handling, as seen during the mail-transmitted attacks. Once they contaminate an area, they're difficult to remove and can keep the area contaminated for decades.

To handle anthrax incidents safely, the aerosol needs to be controlled. Naturally occurring spores are heavy and tend not to re-aerosolize unless actively stirred up. (Postal workers were apparently infected when the sorting machines were cleaned with blowers, which re-suspended spores.) To handle the organism, firefighters should use standard PPE: Gloves, face and eye protection, and an outer garment work well.

To clean the environment, responders can use a 5% bleach solution (1:10 dilution of Clorox), which has the active ingredient of hypochlorous acid. Powder or other contaminated areas should be covered for 30 minutes with paper towels soaked in this solution. This treatment will kill most of the spores.

Exposed people need to strip and shower with soap and water. Because anthrax spores are a common occurrence in many areas, there's usually no need to contain decon water unless required by local or state protocols. Clothes can be washed in a washing machine, but gear and equipment should be treated with bleach if possible. Otherwise, a sporocidal soak available from surgical supply companies can be used.

Anthrax is not an unmanageable threat. Humans have lived with the bacteria for centuries, developed antibiotics that kill it and developed protocols for handling environmental contamination.

Plague

Also known from antiquity, at least 41 epidemics of plague invaded the ancient world. In the 1,500 years following the birth of Christ, the world saw 109 outbreaks, including the great plague of Justinian's time and the Black Death of the 14th century. Between 1500 and 1750, 45 pandemics swept the world, but by the 18th and 19th centuries, the disease had settled into endemic foci, primarily India and Asia. The late 1800s saw the last great epidemic, which was transmitted around world via rat-infested ships and entered the United States through the port of San Francisco about 1906.

The causative agent, Yersinia pestis (Pasteurella), is a non — spore-forming rod. Plague is normally a disease of rodents that's passed host-to-host via fleas. When fleas become infected by biting a diseased rodent, the bacteria multiply and eventually fill the fleas' guts, starving them. The fleas, now frantic, jump from host to host, biting repeatedly in an attempt to feed and injecting the bacteria through the skin.

Human plague comes in three forms: bubonic, septicemic and pneumonic. In the bubonic type, the bacteria spread to the draining lymph node where they create an infected nodule, the bubo. Because the legs are the most common flea-bitten part of human body, buboes are normally below the groin. If untreated, bubonic plague organisms reach the blood stream in up to 80% of cases and cause septicemia. This form of plague has a 50% mortality rate if untreated.

Pneumonic plague can be contracted either by inhaling the organisms or by spreading from other infected areas of the body. In both cases, the patient exhales the organism, making pneumonic plague both contagious and infectious.

Like anthrax, plague causes disease by the growing organisms' release of toxin, and it's susceptible to common antibiotics. Naturally occurring plague, with the exception of the pneumonic form, is not highly contagious. Thus in the wild state, it is easily managed by controlling the rodent populations and their flea infections.

As a bioterrorist weapon, plague is limited to the introduction of infected fleas or to aerosol applications. Because it does not create spores, it is harder to weaponize. Successful weaponization depends on circumventing standard control measures such as flea and rodent eradication or on establishing person-to-person transmission of the pneumonic form. A hazardous response team is unlikely to encounter it. Bleach, as well as a number of bactercidal chemicals, kills the organism.

Smallpox

Although the emergency services need to respect both plague and anthrax, these organisms are neither highly infectious nor contagious. In fact, they are less dangerous than other organisms such as tuberculosis, HIV, and hepatitis B or C viruses that we may handle on a daily basis during medical calls. Smallpox, however, is another story. It's both highly infectious and highly contagious.

Yet another long-known scourge, smallpox probably developed in India and China. By the sixth century B.C., it had infected Arabia and was known to 10th-century Persian physicians. It subsequently appeared in North Africa and Europe, spreading to the West Indies and the Americas with the discovery of the new world.

A member of the Orthopoxvirus group, smallpox is the largest and most complex virus known, infecting only people in its natural state. Once ranked as the world's deadliest disease, it has been eliminated from nature through a vaccination program. Only two smallpox repositories, the CDC and the Institute for Viral Preparations in Moscow, legally exist in the world. However, we have no idea of the possible extent of clandestine stockpiles.

Once injected into the population, this highly contagious disease could spread rapidly through the world. Smallpox sets up housekeeping in the mouth, throat and lungs. From there, it can spread via bedclothes, utensils, saliva or aerosol.

In bioterrorism events, first responders need to take precautions against droplets, airborne matter and standard contact. For decontamination, the virus is susceptible to heat (55°C for 30 minutes) and most disinfectants. However, the virus resists drying and remains viable for months to years in protected, cold environments.

Lesser evils

Once the big names are out of the way, first responders also should be aware of less-likely bioterrorism agents.

Viral hemorrhagic fevers

This diverse group of small viruses causes fevers, which often are accompanied by bleeding, hypotension and shock. They include both old friends like mosquito-borne yellow fever and newly emerging viruses such as Ebola, Marburg and Hantavirus. These viruses, with generally unknown epidemiology, present new dangers.

Of these diseases, a vaccine exists only for yellow fever, although several organisms seem to respond to antiviral therapy with rabavirin. The viruses are susceptible to hypochlorite or phenolic disinfectants. Responders should take contact and aerosol precautions.

The use of these viruses as bioterrorism agents may well be limited. For many of these organisms, their reservoirs and modes of transmission are unknown. The uncertainty creates more difficulty in handling and dispersing, which possibly would deter their current use as bioterrorism agents.

Tularemia

Known since the early 1800s as a small mammal zoonosis, tularemia infects small mammals such as rabbits, hares, voles, mice, water rats and squirrels. Humans acquire the disease through contact with infected animals' contaminated tissues or body fluids; ingestion of contaminated water, food or soil; inhalation of infected aerosols; or via arthropod bites. Soon after its discovery as a potentially severe and fatal illness in humans, tularemia caused widespread epidemics during the 1930s and 1940s when large, water-borne outbreaks occurred in Europe and the Soviet Union.

The causative agent, Francesella tularensis, is a small rod that can be difficult to grow in the laboratory. Although it's non — spore-forming, it is a hardy bacteria and can survive weeks at low temperatures in water, moist soil, hay, straw or decaying animal carcasses. It's one of the most infectious bacteria known; as few as 10 organisms can cause disease. However, there is no human-to-human transmission, making it non-contagious.

Botulism

Best known from home canning incidents, botulism's causative organism Clostridium botulinum is a spore-forming bacterium found in soil. Vegetative cells grow and flourish in environments with little oxygen, and when stressed these cells form spores. Like anthrax spores, they are resistant to heat and can survive incorrect canning processes. When the spores germinate, the growing vegetative cells produce a toxin, one of the most deadly poisons known.

This bacterium kills not by infection, but by its toxin. Although normally ingested, the toxin is so potent that inhalation produces similar symptoms. Since only the toxin causes illness, this disease is neither infectious nor contagious; a person must eat or inhale the toxin. The toxin is not dermally active, but it can be spread by aerosol as a primary bioterrorist attack. Spores spread by aerosol are not a danger.

The toxin is rapidly inactivated by chlorination and extremes of temperature and humidity. Under average conditions, it denatures in about 48 hours and can be made inactive through sporocidal treatment.

Response protocols

As outlined above, all of the CDC-designated A select agents can be spread by aerosol, which is the route most experts feel terrorists will use in methods ranging from crop-dusting airplanes to infiltration of HVAC systems.

As with the anthrax attacks, most biological attacks tend to be covert. Unless there's a visible powder or other manifestation of attack, hazmat responders would have little reason to suspect bioterrorism. As a result, they should assume that all incidents could be biological, just as the emergency services assume all medical aid calls could involve contagious or infectious disease.

Assuming the worst requires us to develop and use protocols for response. For protection against biological agents, responders should wear at least an N100 mask to guard against aerosols, both bacterial and viral. Disposable or sterilizable outerwear and one or two pairs of gloves will protect the skin. For the eyes, closed goggles are best, but some type of protection should be worn at a minimum. If no other threat is detected, this combination of equipment provides the most protection while allowing responders to work with the minimum amount of trouble.

With protection under control, a number of response teams have been investigating field testing for biological agents. If testing works, then the responders know what organisms they're dealing with. However, current field tests have a number of drawbacks: They are inaccurate, producing both false positives and false negatives; the process exposes the responders to the hazard; and testing does not cover all the possible agents.

It's far better to sample the hazard and send it to a laboratory. While testing used to take days, new methods allow specially equipped and trained laboratories to return results within hours of receiving the specimen. These laboratories are members of the Laboratory Response Network and range from local public health laboratories to CDC and Fort Detrick.

To prepare for bioterrorism response, fire departments should contact their local public health laboratory to learn the procedures for having samples tested. The lab also will have information on sampling techniques, which tests to be run and where, and turnaround times. A lab also can supply necessary equipment for sampling and LRN chain of evidence forms. When a sample is submitted, lab workers expect that some preliminary testing has been conducted by the first responders. The lab will want to know if the sample is radioactive, explosive or corrosive to equipment.

The best response approach is to control the aerosols and know how to work with the organisms. Wear respiratory protection — an N100 mask works for both bacteria and viruses. Use gloves but change them frequently, and wear an outer suit along with face and eye protection. Handle samples and swabs with the same caution as other hazardous materials.

Bioterrorism is 1% bio and 99% terrorism. Such incidents are designed to overwhelm health resources, not with the few casualties, but with the many who are well but worried. Responders who understand the organisms that may be involved and treat the scene in a professional manner will reassure the public while protecting themselves.

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A 12-year veteran of the fire service, Kathryn M. Hansen is a captain with the Palo Cedro (Calif.) Volunteer Fire Company who teaches classes on bioterrorism response to fire, EMS and hazmat personel throughout Northern California. She has a bachelor's degree in microbiology from the University of California — Davis and is a licensed clinical laboratory scientist and a certified public health microbiologist. At the request of the California Hazardous Materials Investigators Association, Hansen presented a paper on bioterrorism at their annual convention.

Weapons of War

The use of bacteria and viruses as agents of warfare is as old as history.

During the sixth century B.C., Assyrians poisoned wells of besieged cities with rye ergot, a plant toxin, and Solon used hellebore, a purgative herb, in the siege of Krissa.

When plague broke out in the Tartar army during their 1346 siege of Kaffa (Crimea), troops hurled infected corpses over the city walls. Historians speculate that infected people fleeing this attack helped spread the Black Death in Europe.

In the new world, Pizarro distributed smallpox-infected clothing to South American natives, and during the 1754 French and Indian War, the English presented variola-contaminated blankets to French-supporting natives.

In 1937, Japan started experimenting with at least anthrax and plague for wartime use, and they were not alone in investigating the offensive use of biological agents. The United States ran its own research beginning in 1943. This work, done primarily at Fort Detrick, Md., continued until 1969, when President Richard Nixon signed an executive order halting research and production.

In 1972, the United States and a number of other countries signed the Convention on the Prohibition and the Development, Production and Stockpiling of Bacteriological and Toxin Weapons and on Their Destruction, commonly called the Biological Weapons Convention. Between 1971 and 1972, the United States destroyed its stockpiles of biological agents and munitions; however, defensive work continues on the organisms most suitable to bioweapons and bioterrorism.