ADEs whenever antimicrobial agents are prescribed. At times, sudden clinical changes in elderly patients receiving drug therapy may be related to the drug rather than some underlying disease process. Thus, as a general rule, any unexplained deterioration in mental status or physical capacity should be evaluated as a possible ADE. Conclusion Although the major focus in infectious diseases for the past decade has been on young adults with infection and complications related to the human immunodeficiency virus, the vast majority of serious infectious diseases will be seen in the elderly population. Clinicians who care for adult patients must become familiar and knowledgeable about the biology of aging and the clinical problems in the elderly population. The interrelationship between aging and infectious diseases is one small part of the global problem of aging. It is hoped that by providing data and information about some of the unique aspects of aging and infections in the coming issues of this journal we will improve the care of this most cherished population—the elderly person. References 1. Lyons AS, Petrucelli RJ. Medicine: an illustrated history. New York: Harry N. Abrams, 1978. 2. Kupersmith C. Three centuries of infectious disease: an illustrated history of research and treatment. Greenwich, CT: Greenwich Press, 1998. 3. US Department of Health and Human Services (DHHS), Public Health Service, National Center for Health Statistics: Health United States 1985. D.H.H.S. Publication no. (P.H.S.) 86-1232. Hyattsville, MD: DHHS, 1986. 4. US Bureau of the Census. Decennial censuses of population, 1900–1980 and projections of the population of the United States: 1982-2050 (advance report). Current Population Reports Series P-25, no. 922. Washington, DC: US Bureau of the Census, October 1982. 5. National Center for Health Statistics. Leading causes of death and number of deaths according to age: United States, 1980 and 1993. In: Health United States, 1995. Department of Health and Human Services (DHHS) Publication No. (P.H.S.) 96-1232. Hyattsville, MD: DHHS, 1996. 6. Ben-Yehuda A, Weksler ME. Host resistance and the immune system. Clin Geriatr Med 1992;8:701–11. 7. Beeson PB. Alleged susceptibility of the elderly to infection. Yale J Biol Med 1985;58:71–7. 8. Yoshikawa TT. Important infections in elderly persons. West J Med 1981; 135:441–5. 9. Yoshikawa TT. Geriatric infectious diseases: an emerging problem. J Am Geriatr Soc 1983;31:34–9. 10. Yoshikawa TT. Perspective: aging and infectious diseases: past, present and future. J Infect Dis 1997;176:1053–7. 11. Yoshikawa TT. State of infectious diseases health care in older persons. Clin Geriatr Med 1999;7:55–61. 12. Yoshikawa TT. Infectious diseases, immunity and aging: perspectives and prospects. In: Powers DC, Morley JE, Coe RM, eds. Aging, immunity and infection. New York: Springer, 1994:1–11. 13. Yoshikawa TT. Epidemiology of aging and infectious diseases. In: Yoshikawa TT, Norman DC, eds. Infections in aging: a clinical handbook. Totowa, NJ: Humana Press (in press). 14. Norman DC. Fever and aging. Infect Dis Clin Pract 1998;7:387–90. 15. Yoshikawa TT. Fever in the elderly. Infect Med 1998;15:704–6. 16. Keating MJ III, Klimek JJ, Levine DS, et al. Effect of aging on the clinical significance of fever in ambulatory adult patients. J Am Geriatr Soc 1984;32:282–7. 17. Wasserman M, Levinstein M, Keller E, et al. Utility of fever, white blood cell, and differential count in predicting bacterial infections in the elderly. J Am Geriatr Soc 1989;37:537–43. 18. Levkoff SE, Safran C, Cleary PD, et al. Identification of factors associated with the diagnosis of delirium in elderly hospitalized patients. J Am Geriatr Soc 1988;36:1099–104. 19. Rockwood K. Acute confusion in elderly medical patients. J Am Geriatr Soc 1989;37:150–4. 20. Yoshikawa TT, Norman DC. Infection control in long-term care. Clin Geriatr Med 1995;11:467–80. 21. Alvarez S. Incidence and prevalence of nosocomial infections in nursing home. In: Verghese A, Berk SL, eds. Infections in nursing homes and long-term care facilities. Basel, Switzerland: Karger, 1990:41-54. 22. Yoshikawa TT, Norman DC. Approach to fever and infection in the nursing home. J Am Geriatr Soc 1996;44:74–82. 23. Tresch