Chapter One: Introduction

Background

Troops based in the Arabian Gulf during World War II experienced high morbidity rates from infections. Because of this, coalition troops in the Gulf War were expected to face considerable risk of sandfly fever, malaria, diarrheal disease, and cutaneous leishmaniasis (Quin, 1982). To monitor these expected infections, the U.S. military established a diagnostic laboratory in Saudi Arabia to collect extensive surveillance data.[1] However, history did not repeat itself, and these diseases did not affect a significant portion of those serving in the Gulf regions.

A combination of factors was probably responsible for the resulting low rates of serious infectious disease (Hyams et al., 1995). Rapid medical care was available for acute diarrheal and respiratory infections, reducing morbidity. Also, extensive preventive medicine efforts, including vaccinations, immune serum globulin for hepatitis A prophylaxis, the use of insect repellents, camp hygiene, and monitoring of food and water supplies, helped reduce the transmission of infectious diseases.

Two chance factors may have played an even greater role in reducing infectious disease morbidity: the time of year when most troops were deployed (the cooler winter months) and the location of the deployment (the barren desert) (Hyams et al., 1995). Cold weather reduced the risk of insect-borne diseases at the height of the buildup, as did deployment of most troops away from areas where arthropod vectors and mammal hosts are most plentiful. In comparison, World War II troops were stationed throughout the year and were more likely to camp in oases, river areas of southern Iraq, and urban locations where infectious diseases are a greater threat (Quin, 1982).

Purpose

Still, numerous Gulf War veterans have reported a range of symptoms, some of which are similar to those caused by diseases prevalent in the Gulf region. Therefore, infectious diseases merit consideration as a potential cause of these symptoms.

The scope of infectious diseases is massive, encompassing both the hundreds of known infectious organisms and also the diseases and syndromes they cause. The topic has generated volumes of scientific work and is reviewed well elsewhere. We do not attempt to deal with all infectious diseases in this report. Rather, we focus on known or plausible infectious diseases associated with the Persian Gulf. By known diseases we mean those that were identified in those who served in the Persian Gulf during the Gulf War. Plausible diseases include those known to exist in the area and, more broadly, those whose signs and symptoms are similar to those experienced by Gulf War veterans. We present a short summary of etiology, diagnosis, and treatment and also review the literature related to infectious diseases that were unusual to or of great concern in the Gulf (e.g., mycoplasma disease and leishmaniasis).

Organization of This Document

This chapter provides a general overview of infectious diseases, describing what we know about them and how they are known to behave. It discusses infectious diseases known to have occurred among those who served in the Gulf War and infectious agents common to the Gulf region. The second chapter briefly discusses infectious disease epidemiology (the study of diseases in groups of people as opposed to studies of diseases in individuals).

Following chapters discuss specific infectious diseases by category of infectious organism, including bacterial (Chapters Three and Four), viral (Chapter Five), and parasitic (Chapter Six) infections. Chapter Seven discusses anthrax and botulinum toxin–the two biological agents thought to be most likely to be used by the Iraqis against the troops in the Gulf War. Chapter Eight presents current methods employed to search for new and emerging diseases and the final chapter gives conclusions and recommendations. An appendix contains additional information about Mycoplasma.

Overview of What We Know About Diseases

Despite scientific advances over the years, medical science has not identified every possible disease or every possible interaction between infectious organisms and humans (Lederberg, 1997). For example, not too many years ago, a constellation of clinical findings (e.g., organic pathology) that we now know as the Acquired Immune Deficiency Syndrome (AIDS), was identified in a group of patients. Patients presented with a number of different findings, although all related to the function of the immune system, ranging from unusual infectious diseases to rare cancers. Only later was the Human Immunodeficiency Virus (HIV) identified as the infectious agent responsible for these various manifestations. Similarly, for many years a causative agent for gastritis remained unidentified. Recently, Helicobacter pylori was identified as a common causative and treatable agent. The main difference between these conditions and those of Gulf War illnesses is that symptoms, without measurable clinical findings, are much less definable in the latter.

As the above discussion shows, there is a natural scientific evolution to what we know about infectious diseases. Typically, some unusual combination of findings results in further study, sometimes taking years, that ultimately identifies a cause, sometimes an infectious disease. Given the symptoms of Gulf War illnesses, it is not surprising that an infectious etiology has been considered among the potential causes. Some of the symptoms are found in patients infected with known agents. However, some of the findings suggest that this explanation, while certainly possible, is unlikely.

The Iowa Persian Gulf Study Group (1997) conducted the first population-based epidemiological study to evaluate the health consequences of the Gulf War. The 3,695 subjects who participated in this study were selected from a larger population of almost 29,000 military personnel who listed Iowa as their home. Furthermore, they were specifically selected to represent individuals from all four branches of the military, including both regular military personnel and National Guard and reservists. The interviews for the study were conducted by telephone, resulting in a high rate of participation. Seventy-six percent of the eligible study subjects completed the detailed interviews and the response rate was 91 percent among persons contacted by telephone. The study included a carefully selected comparison group of military personnel who were not deployed to the Persian Gulf but who served during the time of the Gulf War. The Iowa study found that military personnel serving in the Gulf War were more likely than those who did not to report symptoms suggestive of cognitive dysfunction, depression, chronic fatigue, post-traumatic stress disorder, and respiratory illness (asthma and bronchitis). The conditions identified in the Iowa study appear to have had a measurable effect on the functional activity and daily lives of Gulf War veterans and only minimal differences were observed between National Guard or reserve troops and regular military personnel.

Likewise, the Centers for Disease Control and Prevention (CDC) studied Air Force personnel, and that study significantly contributed to our understanding of the health consequences of the Gulf War (Fukuda et al., 1998). That study organized symptoms reported by Air Force Gulf War veterans into a case definition, characterized clinical features, and evaluated risk factors. The cross-sectional questionnaire was sent to 3,723 currently active volunteers from four Air Force populations. Clinical evaluations were performed on 158 Gulf War veterans from one unit, irrespective of health status. A case was defined as having one or more chronic symptoms from at least two of three categories (fatigue, mood-cognition, and musculoskeletal) and was further characterized as mild-to-moderate or severe depending the severity of the symptoms. The prevalence of mild-to-moderate and severe cases was 39 percent and 6 percent, respectively, among 1,155 Gulf War veterans compared to 14 percent and 0.7 percent among 2,520 nondeployed veterans. Fifty-nine (37 percent) clinically evaluated Gulf War veterans were noncases, 86 (54 percent) were mild-to-moderate cases, and 13 (8 percent) were severe cases. The key observation of the study was that Air Force Gulf War veterans were significantly more likely to meet certain criteria for severe and mild-to-moderate illness than were nondeployed personnel (Fukuda et al., 1998). There was no association between the chronic multisymptom illness and risk factors specific to combat in the Gulf War (month or season of deployment, duration of deployment, duties in the Gulf War, direct participation in combat, or locality of Gulf War service). The finding that 15 percent of nondeployed veterans also met illness criteria was equally important and suggests that multisymptom illness observed in this population is not unique (although less frequent) to Gulf War service. The clinical evaluation component of the study found that neither mild-to-moderate nor severe cases were associated with clinically significant physical examination or routine laboratory abnormalities. However, Gulf War veterans classified as having mild-to-moderate and severe illness (cases) had a significant decrease in functioning and well-being compared with noncases.

Common Illnesses in Gulf WAR Veterans

Table 1.1 shows the distribution of complaints expressed by veterans.[2] When those with symptoms were medically evaluated, a specific diagnosis was made for 77 percent. Among veterans with symptoms who did not receive a specific diagnosis, a characteristic physical sign or laboratory abnormality was not observed.

Table 1.1
Common Complaints of Gulf War Veterans
(Persian Gulf Health Registry with complaint data available)

Common Complaints of Individuals Who Served in the Gulf War
(n = 18,075 CCEP Participants)

Similar data are available for individuals who remained on active duty. They have been encouraged to refer themselves for care. Data on these individuals are maintained as part of the Department of Defense (DoD) Comprehensive Clinical Evaluation Program (CCEP) (1996). Table 1.2 describes the common complaints expressed by the 20,000 CCEP registrants as of April 1996 (IOM, 1996; DoD, 1996). All complaints are recorded, including the chief complaint (i.e., the main reason for seeking care).

The symptoms and complaints listed in Tables 1.1 and 1.2 are real. In fact, most of us have experienced one or more of them. It is important to understand, therefore, whether Gulf War veterans experience these symptoms and complaints more than they would have had they not served in the Gulf War. If the rate of these symptoms and complaints is higher than that of the general population, we must then consider whether the increase is or might be related to infectious diseases.

The following discussion places the roles of infectious diseases, and the spectrum of illness experienced by Gulf War veterans, into three general categories:

1. Infectious diseases known to have occurred among Gulf War troops.
2. Infectious diseases known to exist in the Persian Gulf region but not diagnosed in any of our troops.
3. Other infectious diseases considered as possible causes of Gulf War illnesses.

Infectious Diseases in Gulf War Troops

The most complete evaluation of the effect of infectious diseases on Gulf War troops covers cases reported during Operations Desert Shield and Desert Storm (August 1990 to March 1991) and any cases up to early 1994 that were reported and attributed to service during that period (Hyams et al., 1995).

Gastrointestinal Diseases

Gastrointestinal (GI) complaints were the most frequent symptom among deployed U.S. troops (Hyams et al., 1991). Most who experienced transient symptoms found that they resolved after a few days. Although present throughout the deployment, GI problems were most frequent during the early days (August and September 1990), probably because fresh produce was obtained locally (from Mediterranean and Asian sources). In October 1990, once exposure to fresh produce was stopped, the rate of GI complaints declined dramatically. By November/December, the rate dropped to about 0.5—1.0 percent seeking treatment per week, similar to what is experienced among civilians in a community health care setting. Table 1.3 lists the gastrointestinal pathogens identified among symptomatic Gulf War troops.

Respiratory Diseases

Respiratory diseases were common among troops stationed in the Middle East. In an epidemiological study of 2,598 male ground troops, 34 percent reported a sore throat, 43 percent a cough, and 15 percent a persistent runny nose (Richards et al., 1993). Not surprisingly, as in civilian environments, symptoms were treated without confirming a specific cause. Specific studies to look for a cause for disease were undertaken in only 68 individuals (Table 1.4).

Other Diseases

Other diseases known to occur in the Middle East were experienced by a small number of individuals (Table 1.5).

Table 1.3

Gastrointestinal Infections Identified Among
Individuals Serving in the Gulf War

Respiratory Pathogens Identified Among
Individuals Serving in the Gulf War

Other Infections Identified Among
Individuals Serving in the Gulf War

Infectious Diseases in the Persian Gulf but not
Identified in Gulf War Troops

Experience with previous wars in the Middle East led military and civilian experts to predict that the number of patients who might experience infectious diseases native to the Persian Gulf would be higher than was actually experienced. Several specific infections were known to exist in and around the Persian Gulf region, yet they were not identified among U.S. troops. These infectious diseases include those listed in Table 1.6.

Table 1.6

Infections Common in the Persian Gulf
But Not Diagnosed Among Individuals
Serving in the Gulf War

Other Infectious Diseases Considered

Several other infectious diseases have been considered as possibly related to Gulf War illnesses,[3] although they are not specific to the region in which United States troops were deployed. Specific diseases considered are listed in Table 1.7.

Table 1.7

Other Infections Possibly Related to
Gulf War Illnesses

Endnotes

[1] gulflink.health.mil Medical Surveillance during Operations Desert Shield/Desert Storm, November 6, 1997 (www.gulflink.health.mil/nfl).

[2] Veterans in the Persian Gulf Health Registry with complaint data available.

[3] As noted in the summary, in this volume the term Gulf War illnesses is used to indicate the range of undiagnosed illnesses experienced by veterans of the Gulf War. We use the term to refer to the sum of conditions experienced by veterans of the Gulf War; we do not imply that there is or is not one disease.