[5]. Thus, although the advances made in reducing deaths and complications related to infections have increased our life expectancy and resulted in a large population of elderly people, paradoxically, among people in this age group we are now again encountering infections as a major health care problem. Some Unique Aspects of Infections in the Elderly Risk factors and common infections. Older persons generally have greater susceptibility to infections than younger adults. It is well known that aging is associated with immune dysfunction, especially in cell-mediated immunity [6]. However, elderly persons also suffer from a variety of chronic disorders, some of which affect the integrity of host resistance to infections. It is somewhat unclear whether the immune changes associated with aging are sufficient in themselves to explain the greater susceptibility of infections in the elderly or whether agerelated disease (and its adverse impact on host resistance) is more important in this process [7]. Several studies have shown that certain infections occur more often in elderly persons; morbidity and mortality from infections are also higher that they are among younger adults [8–11]. Urinary tract infections, lower respiratory tract infections, skin and soft tissue infections, intra-abdominal infections (cholecystitits, diverticulitis, appendicitis, abscesses), infective endocarditis, bacterial meningitis, Downloaded from https://academic.oup.com/cid/article/30/6/931/433911 by guest on 03 December 2021 932 Yoshikawa CID 2000;30 (June) tuberculosis, and herpes zoster appear to have a special predilection for elderly persons. Moreover, the mortality rates of most of these infections are at least 3 times higher among elderly patients than among younger adult patients with the same disease [11–13]. Probably several factors contribute to this higher morbidity and mortality: age-related reduced physiologic reserve capacity, decreased host resistance, chronic underlying diseases, delays in diagnosis and therapy, poor tolerance to invasive diagnostic and therapeutic procedures, delayed or poor response to antimicrobial therapy, greater risk and incidence of nosocomial infections, and higher rates of adverse reactions to drugs, including antibiotics [12]. Altered clinical manifestations. Fever, the cardinal manifestation of infection, may be absent or blunted in elderly patients with serious or life-threatening infections [14, 15]. Studies have indicated that as many as 25% of elderly patients with such infections may fail to elicit or demonstrate a febrile response. Alternatively, the presence of fever in an elderly person is generally associated with a serious underlying infection, usually of bacterial origin [16, 17]. Older persons with infections may also manifest their disease atypically, with acute confusion or delirium as the dominant finding [18, 19], or they may have a subacute course with symptoms of weakness, anorexia, weight loss, falling, urinary incontinence, or loss of physical functional capacity (e.g., walking, dressing, bathing, doing household chores, going to the bank, or driving). Such atypical clinical presentations of infections delay diagnosis and early treatment in this already frail population. Infections in a long-term care setting. In contrast to younger adults and children, the vast majority of people institutionalized in long-term care facilities, such as a nursing facility (nursing home), are the frail and elderly. Such persons are usually cognitively impaired and physically dependent; the mean age of nursing facility residents is 80–85 years. These residents are highly vulnerable to infections because of their frailty, physical disabilities and altered host resistance. Furthermore, a closed, institutional environment favors regular exposure to microorganisms because of frequent contacts with other residents and staff; limited ventilation, filtration and removal of recirculated air, which could contain pathogens; and unrestricted movement of other residents who may be infected [20]. Approximately 1.5 million infections occur each year in nursing facilities throughout the United States [21]. The reported incidence of infections in such facilities varies depending on the type of the institution and its residents but is ∼10–20 infections per 100