'Pathogens for Knuckleheads': The Enemy Within - Invisible & Infectious

Throughout the ages, life has fostered competition between and within different species. Human as well as non-human societies and cultures have continuously been seeking competitive advantages over others, and in the modern world that unceasing quest has paved the way, within humans, for so many new technologies that it is sometimes easy to forget why and how such rivalries originated.

It also is easy to forget, though, that humans are not the only species to thrive on fierce competition. Even at a microscopic level organisms are constantly vying to out-compete their hosts. However, until the modern era of technology, few humans, except scientists, were even the slightest bit aware of the existence of life – non-human life in particular – as seen through a microscope, but invisible to the human eye.

Even today, if one were to pose a relevant question – “What is a pathogen?” – the responses from the American people would probably range from ballpark “guesstimates” to in-depth scientific analyses – and elicit more than a few blank stares. But when pathogens pose a serious threat to human life – be it in a massive disease outbreak or through an act of bioterrorism – the nation’s collective ignorance of “Pathogen 101” basics can no longer be acceptable.

Today, most U.S. first responders are reasonably knowledgeable about the massive destruction and loss of life that could be caused by chemical, radiological, and nuclear weapons – as well as, more recently, the somewhat smaller-scale threats posed by improvised explosive devices (IEDs). But biohazard-specific training has in comparison been somewhat neglected – for a number of reasons, including the fact that the topic is not only very complex but also frustratingly difficult to deal with effectively. In addition, the various educational and outreach programs that have focused on biological agents usually concentrate on events in recent memory – the anthrax-laden letters mailed shortly after the terrorist attacks of 11 September 2001, for example, and the installation and use of hand-sanitizing stations during and since the H1N1 flu pandemic.

Nonetheless, developing a comprehensive understanding of pathogens as a whole – not just as a “flavor of the month” type of recent threat – is critical for responding to and mitigating future biological threats. Following are brief comments on some but by no means all of the more important facts and theories – “Pathogens for Knuckleheads,” as one expert described it – about the nature of pathogens, how to recognize them, how to cope with them, how they are affecting U.S. public policy, and what changes, both in the threat itself and in the systems and processes developed to cope with the threat, might be expected in the foreseeable future.

“Pathogen”: What it is; what it does. The word pathogen comes from the Greek words “gen” and “pathos,” which mean “give birth to” and “suffering.” In its most basic form, a pathogen is an infectious agent that causes disease. There are many different ways the disease can be triggered, and many different types of organisms that can be involved.

Pathogens are living creatures: The term “pathogens” usually refers only to living “things”: bacteria, viruses, fungi, parasites, and prions. One might not think of these microscopic creatures as “living” in the same way a cat or dog – or a human being – lives, but each has very specific “life styles,” lives in certain well defined environments or habitats, and goes through more or less the same cycles of life, and death, as dogs, cats, humans – and other much larger creatures visible to the human eye – live, grow, procreate, and die.

Sometimes the lines get blurred: The assertion that all pathogens are living organisms is mostly true, but with certain qualifications. “Science” is about truth, accuracy, and precise definitions – but in real life is seldom if ever absolute. For example, it has been argued that prions and viruses are not really “living” as most humans understand that word. In the case of botulism, the bacterium itself is not the pathogen but, rather, the deadly toxin the bacterium produces. Infections caused by anthrax occur only from certain strains of Bacillus anthracis, which contain plasmids encoded with an anthrax toxin. As a general rule, though, pathogens usually refer to something “biological” in nature – i.e., either living, or derived from a living “thing” of some type.

There is no cure-all in the modern medicine bag: In order for a pathogen to survive, it must first invade and then take over the cells of a host; here, the word “host” means another living thing – something much larger than the pathogen itself. The human immune system provides a formidable natural defense against most if not all of these foreign invaders – and modern science has significantly strengthened the human side of the battle by creating a broad and growing spectrum of antibiotics, vaccines, fungicides, and anti-viral medications.  

Here it should be noted that, as many cold sufferers already know, viruses do not respond to antibiotics. But the scientific facts are much more complicated than that. Each pathogen requires different response reactions, tailored to defeat specific organisms. Anthrax infections respond well to such antibiotics as doxycycline and ciprofloxacin, for example, but tularemia infections respond better to streptomycin and gentamicin. Also worth noting: Ricin is a toxin derived from a plant (the castor bean) – not a bacterium – and there is no currently known antitoxin for it. (The “cure” currently favored requires decontamination of the exposed victims, and use of a stomach pump.)

There are many different ways a pathogen can be transmitted: There has been considerable medical progress in recent years in such disparate fields related to and/or affecting human health as personal hygiene and both food and water safety. Unfortunately, though – and no matter how sophisticated human defenses are – pathogens always seem to find a way to win at least some of the battles. Contaminated food or water, for example, are still among the primary sources of pathogen transmission. What makes these battles even more difficult, though, is the fact that pathogens themselves have evolved in many ways over the years to “outcompete” more advanced organisms – such as mankind. Some pathogens can be transmitted person-to-person via body fluids; others are concealed in the air droplets caused by a cough or sneeze; and still others live, thrive, and swim through the human bloodstream. In addition, a number of pathogens are described as being “opportunistic” – meaning that they are naturally resident in the human body as healthy bacteria. But they also can become extremely harmful, and even fatal, when something happens to upset their natural balance – a staph infection following surgery, for example.

Bioterrorism is not a modern concept: Pathogens possess certain unique characteristics that make them particularly useful as weapons – and they have, in fact, been used as extremely lethal weapons for hundreds and perhaps thousands of years. Biological agents are, in fact, the oldest of the “NBC triad” (nuclear, biological, chemical) of lethal agents. Today it is easy to remember the “anthrax letters” mailed to certain congressional offices (and other addresses) following the 9/11 terrorist attacks – but the use of bioterrorism as a weapon of war started much earlier. They were used in the 1300s, for example, when the Tartars catapulted plague-infected corpses over the walls of Kaffe (Crimea). Four centuries later, during the 1700s, Sir Jeffrey Amherst ordered British troops to give smallpox-infected blankets to some troublesome Indian tribes. In World War II, German troops, and scientists, used anthrax to kill “enemy” (i.e., U.S. and Allied) horses and mules, and in 1984 members of the Rajneeshee Cult sprayed salmonella on salad bars of almost a dozen restaurants in The Dalles, Oregon – sickening more than 750 people.

Not incidentally, the ability to obtain and use pathogens as weapons is not as difficult as one might think. Until recently, many toxic agents could be obtained from reference collections – created for research purposes, primarily – and the devices and systems used to disperse agents are usually easy to find available on the open market. Moreover, because pathogens are living creatures they have a natural tendency – like dogs, cats, and humans – to replicate and propagate themselves by creating new generations of their own species.  

Bioterrorism pathogens as categorized by the CDC: “Category A” agents are high-priority organisms that are defined by the CDC (the U.S. Centers for Disease Prevention and Control) as posing a significant risk to national security because they can be easily transmitted from one person to another. In addition, because they also may cause a large number of deaths in a very short time, Category A agents could easily, and rapidly, cause public panic and/or massive social disruption. Among the best known examples of Category A agents are anthrax, smallpox, plague, tularemia, and botulism.

“Category B” agents are second highest on the CDC priority list, because they are relatively easy to disseminate and would result in moderate amounts of illness (and somewhat lower death rates). Among the best known “Cat B” agents are brucella, ricin, and salmonella.

“Category C” agents are “emerging” diseases that do not – so far, at least – have a big enough “footprint” to be considered Category A or B.

Recognizing a bioterrorism attack or outbreak: If there is an incident in which a potentially hazardous “bio substance” has been released, it is the responsibility of local hazmat teams – those that have been properly trained on how to respond – to keep emergency managers and other decision-makers aware of how they assess the situation. A major problem with identifying biohazard agents in the field, though, is that such agents are much more complex than chemicals or explosives – and require much more sophisticated technologies to identify with an acceptable degree of accuracy.

The most sensitive and most accurate way to test for pathogens in the field is to use Real-Time PCR (polymerase chain reaction) systems and devices. PCR searches out the pathogen’s unique DNA and uses it to make a positive identification. After being tested, the samples are sent directly to a regional laboratory to be “grown” in a carefully controlled culture – and at the same time quantified in accordance with other DNA standards.

There are several other factors to consider if it is not blatantly obvious that there has been an biological attack per se. Most pathogens have what is called an “incubation period” – i.e., a certain length of time when there are no obvious symptoms of disease, but the disease is still active and quite possibly already contagious.  This period is where public health monitoring comes into play. Epidemiologists regularly, and routinely, evaluate hospital statistics in search of unexpected spikes in fever, rash, gastrointestinal illness, and/or other disease symptoms. If a drastic increase or growth is identified in any one of these symptomatic areas an immediate investigation should be launched to discover the cause.

Responding to an incident involving pathogens: When a potential source of infection has been identified, there are several escalating methods of limiting the spread of the pathogen. The specific response selected will vary, though, in accordance with the type of pathogen that has been identified. If there has been an intentional release of anthrax, to cite but one plausible example, prophylactic medications may be provided, and those persons infected may simply be permitted to return home – this is a safe option, because anthrax is not capable of being spread from one person to another. However, if an infectious agent such as smallpox or plague is intentionally released (or appears as a natural outbreak of either of those diseases), voluntary isolation and/or quarantine are more likely to be considered.

The isolation process separates a sick person from those who are not sick, but dealing with the infection, and caring for the sick, requires health providers, and visitors, to wear effective personal protective equipment – e.g., gowns, masks or respirators, and gloves – while treating those who are infected. Quarantine is somewhat less drastic than isolation, but it does restrict the movements of otherwise healthy persons who may have been exposed to a communicable disease so that the pathogen is not spread more widely during its incubation period. A recent well publicized event worth noting: Quarantines were used widely, and successfully, in Canada during the 2006 SARS (severe acute respiratory syndrome) outbreak.

Communicating with the public: During any incident or event that is suspected to involve potentially deadly pathogens, it is crucially important to provide accurate and reliable information to the public – quickly, and on a continuing basis. Experience shows that tailoring presentations to the public’s attitude – and remembering to reiterate the most important parts of the message over and over again, as many times as is necessary – will yield the best results. These messages should be simple, straightforward, honest, accurate, realistic but not alarmist, and should include specific instructions on where to find additional information – a hotline call number for continuing updates, for example. Empowering citizens by using essential communications tools during times of unusual stress can be one of the most effective way to mitigate fears and restore public confidence.

Dangerous pathogens will undoubtedly be a continuing threat to mankind for generations to come, and on occasion may be able to “out-compete” humans. But with consistent and improved training of healthcare professionals, continued monitoring, and advanced testing capabilities it now seems possible, for the first time in recorded history, to prevent pathogens from “outsmarting” humans as well.