In the past half-century, there have been dozens of major armed conflicts involving millions of combatants from numerous countries throughout the world. Several of these wars have been multinational in scope and have involved the deployment of large numbers of ground forces from their home countries to distinct areas of conflict in developing portions of the world, such as southwestern and central Asia (e.g., Iraq, Afghanistan) and Africa. In the United States alone, there are estimated to be more than 18 million living veterans, many of whom served in combat theaters.
Troops who are deployed as combatants or in other military capacities on foreign soil are at heightened risk of acquiring infectious diseases on the bases of intimate human and environmental exposures and immunologic naiveté to local endemic or enzootic pathogens. This risk is magnified by the crowded social conditions engendered by mass troop deployments, infrastructure destruction, and population displacement; it is further amplified by vulnerabilities in public health, such as lapses in hygiene and sanitation that invariably accompany armed conflicts. The clinical spectrum of communicable illness acquired in this setting includes acute infections in the combat theater, acute infections with delayed clinical manifestations, and chronic or relapsing infections. The latter two scenarios have the potential to cause illness in veterans returning from foreign wars.
The impact of acute infectious diseases of war, once a major cause of noncombat mortality, has significantly lessened in modern conflicts, largely because of the use of preventive vaccines, improved hygiene and sanitation, and the early institution of antimicrobial therapy as clinically indicated. Nonetheless, such acute diseases remain an important cause of morbidity in deployed military personnel (Table S5-1). Several, such as influenza, meningococcal meningitis, hepatitis A, and adenoviral respiratory disease, can largely be prevented by routine vaccination of troops. Others, such as bacterial gastroenteritis and viral respiratory tract infections, continue to represent common causes of minor morbidity among deployed forces. The incidence of several other acute infections, such as malaria and dengue, can be favorably impacted—although not completely abrogated—by the use of classic public health interventions: chemoprophylaxis, personal protective measures, and vector control. Infections that have short incubation periods and are acquired just days before departure from a combat theater may theoretically become clinically manifest only upon the return of troops to their countries of origin. One such example was a cluster of African tick typhus cases that occurred during short-term U.S. troop deployments to Somalia and Botswana in the early 1990s. However, because most acute infections with brief clinical incubation periods are self-limited or responsive to treatment, they are not typically seen in returning war veterans and, with the exception of malaria, will not be addressed further in this chapter.
TABLE S5-1Acute Infectious Diseases of War That Have Brief Clinical Incubation Periods and Therefore Are Likely to Cause Symptomatic Illness in Military Personnel during Deployment