The purpose of this chapter is to:

Part 1 will discuss the prevention and management of infectious diseases arising from wilderness environments and agents. Part 2 will discuss the treatment of general infectious diseases that occur in a wilderness setting.

Before discussing the world of infectious diseases, here is a quick review of some medical terminology that is used throughout this chapter.

Disease: an interruption, alteration, or cessation of one or more normal body functions, systems, or organs. Diseases have recognizable etiologic or causative agents and an identifiable collection of signs and symptoms, along with consistent anatomic alterations.

Communicable diseases: diseases that can be spread directly from one human to another, or from an animal to a human via a vector.

Contagious diseases: diseases that are spread directly from one person to another.

Infectious diseases: diseases caused by or resulting from the presence and activity of microbiological agents: viruses, bacteria, fungi, or parasites.

Pathogen: any microorganism capable of causing disease.

Vector: the method by which an infectious disease is transmitted: waterborne, food-borne, or insect-borne.

Fomite: a nonliving vector that can harbor or transmit an infectious disease. Examples in the wilderness include flashlights, toothbrushes, foam pads, etc.

Reservoir: living or nonliving material on which an infectious agent multiplies, develops, and is dependent upon to survive.

Host: the organism in or on which an infectious agent lives and causes symptoms. The infectious agent is dependent on the host for its energy.

Symbiosis: the biologic association of two or more species for their mutual benefit. Both the host and the microbe profit from the relationship.

Parasite: an organism that lives on or in another at the expense of that host. The parasite benefits and the host suffers.

Commensal: a relationship where one organism benefits from another but not at any cost to the other. Although the microbe lives in the host, it does not cause the host any harm.

There is a constant life and death struggle taking place on us and in us. As long as we are winning this battle, we are not even aware of it. Our ability to survive and thrive is totally dependent upon our ability to constantly and consistently wage war, defeating the enemy we cannot see. This is the war of our own personal world, the war that is constantly being waged by infectious disease pathogens and our immune system.

It is imperative that all medical providers understand pathogens, the risk of exposure to pathogens, and how our immune system protects us from these pathogens. Since infectious diseases play a role in providing care, it is equally important to understand the pathophysiology, signs and symptoms, and principles of treatment of infectious diseases.

We are not alone on this planet. With approximately 7 billion people, there are billions of infectious disease agents trying their best to elude and overwhelm our immune systems—in other words, to make us part of their food chain. These billions of microbiological agents are commonly known as “bugs,” “germs,” parasites, viruses, bacteria, yeast, fungi, and microbes. They come in all sorts of shapes and sizes. Most microbes are harmless to us; they are not pathogens, and many are very beneficial to us. But, the pathogenic organisms thrive at our expense, causing infectious diseases.

The key to a long life is actually quite simple: knowing how to avoid the bad bugs, the pathogens, so that we stay on top of the food chain. In other words, to consume and not be consumed.

Through the excellent sanitation laws and practices in developed nations, we are virtually oblivious to the risks of infectious diseases. Although from time to time the media alerts us to various infectious disease problems, we generally feel that we can trust that the food and water we are served in restaurants or at home is properly prepared and safe to eat.

When we hear the news that it is flu season, alarmed, we rush off to our doctors’ offices for flu shots designed to boost our immune system specifically against certain strains of the influenza virus in the hope that we not be stricken by “the bug.” This preventive measure is great. But, in the process, we have become so dependent on a “quick fix” that we are no longer educated about viruses, and may even be apathetic regarding their risks—cavalier in our assumption that catching influenza will not happen to us, and if it does, our doctors will take care of us. Nice thought, but as with the case of most viruses, not necessarily true.

Most infectious diseases are curable, but the experience of enduring the illness may not seem worth the suffering. Still others are incurable, and they can make us sick for life or even end our lives prematurely.

Infectious diseases can be transmitted in many different ways. Table 20.1.1 describes some of the ways this transmission can occur.

Direct contact occurs when the care provider comes into direct contact with a body fluid: blood, urine, feces, vomitus, sweat, tears, cerebrospinal fluid, sputum, phlegm, vaginal secretions, sperm, or a purulent drainage from a wound or skin infection.

Direct contact contamination is prevented by wearing appropriate personal protection equipment such as gloves, gowns, and eye protection. We also must be careful to avoid accidental needle sticks. These precautions are part of body substance isolation.

Indirect contact refers to contact with a body fluid that has been deposited onto a surface, such as a sleeping pad, cookware, or any camping or rescue gear. Surfaces that can play this role are termed fomites. Infectious droplets coughed into the air and then inhaled are another example of indirect contact.

Prevention of indirect contact contamination includes protecting the airway by wearing a surgical mask, protecting the eyes with glasses or goggles, wearing gloves and gowns, and handwashing before and after providing patient care.

Vector-borne contact refers to disease that is spread by ingestion (water or food) or by stings or bites by an arthropod (eg, insect, tick).

Insect-borne contact is a subset of vector-borne contact and refers specifically to the biting, blood-sucking insects, such as mosquitoes, black flies, sand flies, and others that can spread a disease from a reservoir in nature to a host.

Prevention of insect-borne diseases requires diligently avoiding insect bites by using insect repellants/insecticides, dressing appropriately, and sleeping under mosquito netting. Many insect repellants are ineffective, while insecticides, by definition, kill insects. Diligent research will reveal what is available in a local wilderness EMS operational environment. In some cases, there are prophylactic measures that can be taken to prevent certain diseases.

Waterborne and food-borne methods of contact describe diseases that are spread by drinking water or eating food that has been contaminated, usually via the oral-fecal route.

Prevention of waterborne and food-borne illnesses is accomplished by drinking water that has been properly purified by boiling, filtration, or chemically treated with chlorine, iodine, or UVC light, and by eating foods that are properly prepared, well cooked, and, if appropriate and necessary, served hot. Even bottled water is not without risks; although safe if the bottle’s original seal is intact, there is no way of telling if the water is safe if the container has been refilled. This is more likely to be a problem in developing countries where water treatment and restaurant laws are not as strict or strictly enforced.

The next step in the process of understanding infectious diseases is an overview of the world of microbiology, the biology of animals that are typically only visible with the aid of an electron or light microscope.

The list begins with the smallest known infectious particles, progresses to single-celled organisms, and ends with multicellular organisms (Table 20.1.2).