Approach to infection in the older adult

INTRODUCTION — Infection is an important cause of death in many individuals aged 65 years and older and is a contributor to death for many others [1]. Infection also has a marked impact on morbidity in older adults, exacerbating underlying illnesses and functional decline.

Multiple biologic and societal factors account for the increased susceptibility of older adults to infection and their poorer outcomes when infected. These factors may also alter the presentation of infectious syndromes in older adults and necessitate greater attention to subtle clinical changes during the course of treatment.

The aspects of infectious diseases unique to the older adult will be reviewed here. When available, recommendations for diagnostic evaluation and therapy for the older adult are provided. Multiple topics throughout UpToDate present detailed discussions of pathologic, diagnostic, therapeutic, and preventive aspects related to specific infections.

INCREASED RISK FOR INFECTION — Fundamental alterations in quantitative and qualitative immune responses occur with aging, a process that has been called immune senescence. (See "Immune function in older adults".)

Age-related physiologic changes include:

●Increased risk of invasion by pathogenic organisms due to alterations in the barriers posed by the skin, lungs, and gastrointestinal tract (and other mucosal linings) [2].

●Increased risk of intracellular pathogens due to changes in cellular and humoral immunity, including decreases in specific cell populations, loss of the proliferative capacity of immune cells, and decreased production of specific cytokines (eg, interleukin 2) [3,4].

●Impaired defense against fungal and viral pathogens due to impaired signal transduction after cytokine binding.

●Decreased antibody response to vaccines, related to reductions in toll-like receptors [5], senescence of CD8 cells [6], reductions in naïve CD4 cells [7], and changes in B-cell biology [8].

●Impaired immunoglobulin production and specificity of antibody responses associated with reductions in naïve B cells [9,10].

Older adults with chronic diseases (eg, diabetes, chronic obstructive pulmonary disease, or heart failure) have greater impairment in immunity, resulting in greater susceptibility to common infections and poorer vaccine responses [3].

The risk of infection in older patients is often heightened by communal residence or other social institutions such as nursing homes, daycare programs, or senior centers [11-17].

PRESENTATION OF DISEASE — It has long been recognized that older adults can have severe infection that does not manifest with the typical signs or symptoms characterizing disease in younger adults [18,19].

Suspicion for infection — Older adults with infection may lack fever or localizing, infection-specific symptoms or signs. As an example, rather than a fever, productive cough, and pleuritic chest pain, pneumonia in an older adult may present as a low-grade temperature elevation to 99ºF and an increased oxygen requirement. Infection in older patients may be associated with nonspecific symptoms such as increased confusion, falling, and anorexia [20]. However, these nonspecific symptoms are common in older adults and do not have high positive predictive value for infection [21]; they do not necessitate empiric treatment but should prompt attempts to elicit localizing signs on physical examination, medication review, and other diagnostic tests or supportive measures such as oral hydration. The presence of new fever, hypothermia, delirium, or new-onset hyperglycemia should prompt an evaluation of infection. However, behavioral changes in by themselves do not require an exhaustive evaluation for infection. If empiric treatment is initiated, it is important to discontinue it promptly if diagnostic tests are negative [22-24].

Older adults with cognitive impairment tend to have behavioral changes due to a variety of reasons including waxing and waning of underlying cognitive impairment. In these situations, careful clinical evaluation (including presence of delirium) by their primary care provider is important. Cognitive impairment further contributes to the atypical presentation of infections in older adults due to the reduced capacity to communicate symptoms. Clinicians may need to pursue objective assessments such as laboratory and radiologic evaluations at a lower threshold in cognitively impaired patients, unless advanced directives and goals of care dictate otherwise. However, in situations of only new-onset behavioral symptoms without any other localizing symptoms and in absence of delirium, further evaluation for infection may not be useful. In these cases, noninfectious etiologies should be carefully considered [20].

Given the often atypical and subtle ways in which infection presents in older adults, there has been substantial interest in biomarkers such as C-reactive protein and procalcitonin to help identify infection. Unfortunately, varying cutoffs for "normal" values have led to wide variation in sensitivity and specificity for these assays [25,26]. The use of procalcitonin in evaluation of infection and antibiotic use is discussed in detail elsewhere. (See "Sepsis syndromes in adults: Epidemiology, definitions, clinical presentation, diagnosis, and prognosis", section on 'Laboratory signs' and "Evaluation and management of suspected sepsis and septic shock in adults", section on 'De-escalation and duration of antibiotics' and "Procalcitonin use in lower respiratory tract infections".)

Fever definition — Relatively healthy, community-dwelling older adults may be appropriately managed using conventional definitions of fever. In these patients, a temperature >38°C (100.4ºF) indicates a potential for serious infection, while hypothermia relative to baseline body temperature may signify severe infection or even sepsis [27].

However, in frail, older adults, fever is absent in 30 to 50 percent, even in the setting of serious infections such as pneumonia or endocarditis [28,29]. Thus, we use a lower threshold for fever in frail, older patients:

●Single oral temperature >37.8°C (>100ºF)

●Persistent oral or tympanic membrane temperature ≥37.2°C (99.0ºF)

●Rise in temperature of ≥1.1°C (≥2°F) above baseline temperature

The blunted febrile response in older adults is due to impairment in multiple systems responsible for thermoregulation (eg, shivering, vasoconstriction, hypothalamic regulation, and thermogenesis by brown adipose tissue) [30]. Revisions of parameters used to identify "fever" in frail older adults have thus been suggested [27,31,32]. Infections can also present with hypothermia.

Following criteria are recommended to define hypothermia:

●Two or more temperature measurements ≤95.9°F (≤36.0°C) [33]; or

●Two or more temperature measurements documenting a decrease in temperature of >2°F (>1.1°C) from the baseline [20]

ANTIBIOTIC MANAGEMENT — Antibiotic management in older patients is influenced by age-related pharmacokinetic changes, comorbidities, and risk of exposure to, or infection with, multidrug resistant organisms. Absorption of oral or enteric drugs is often diminished due to increase in gastric pH and gastric emptying, atrophy of mucosal surfaces, and reduced gastric motility. Systemic distribution of antibiotics may be influenced by factors such as drug solubility, serum proteins, and cardiac output. Since most antibiotics are eliminated by hepatic and renal metabolism, rates of elimination are usually impacted. In addition, patient adherence may be decreased due to poor cognitive function, impaired hearing or vision, polypharmacy, and medication side effects. In general, antibiotic use is very common in older adults and a significant proportion are inappropriately prescribed due to lack of appropriate indication, overly broad spectrum, or a longer duration than necessary.

Choice of agent — The choice of initial antibiotic is generally the same as in younger patients for most routine infections. Choice of agent should be guided by the knowledge of local antimicrobial susceptibility and resistance patterns through facility antibiograms or public health information networks. Watchful waiting with close monitoring and hydration may be appropriate in milder cases of infection while conducting diagnostic workup, particularly in milder cases of urinary tract infection (UTI) without concerning physical findings. However, consideration for broader empiric coverage may be warranted in some situations:

●Increased risk of infection with drug-resistant organisms, due to residence in an institution, recent hospitalization, dialysis treatment, recent antibiotic exposure, or indwelling devices [13,14].

●Broader initial coverage may be appropriate in seriously ill older adults in whom sepsis, severe pneumonia, or other life-threatening infections are more likely to be suspected [34].

However, it is very important to narrow the antibiotic regimen when cultures are available to decrease the risk of engendering antibiotic resistance and of Clostridioides difficile disease.

Antibiotic interactions are also a major consideration in antibiotic selection, as these may occur with many medications commonly prescribed in older adults, particularly those with a narrow therapeutic index. For example, significant interactions with commonly prescribed antibiotics are seen for warfarin, antacids and H2 receptor antagonists, and digoxin. For some antibiotics, the direction of the interaction may be hard to predict and may even be biphasic (eg, rifampin increases concentrations of some drugs initially, but induction of hepatic enzymes may lead to reduced drug concentrations in a few days).

Dosing — The distribution, metabolism, and excretion of many drugs is altered with age [35], most importantly due to a decrease in glomerular filtration rate (GFR). (See "Drug prescribing for older adults", section on 'Renal impairment'.)

Antibiotics for serious infections should be dosed according to the estimated GFR throughout the treatment course. Although "start low, go slow" can be an appropriate dosing strategy for other medications in older patients, this does not apply to antibiotics, for which maintaining drug levels in the therapeutic range is essential. Consulting a pharmacist for dosing recommendations can be helpful.

Certain antimicrobials (eg, fluoroquinolones) that have concentration-dependent activity work best when levels of drug far exceed the minimum inhibitory concentration, and this is more critical for achieving successful outcomes in older adults than in young adults [36]. Susceptibility of organisms to certain antibiotics, including penicillin, amoxicillin, and other beta-lactam drugs, are predicated based on serum levels achieved by dosing at the higher end of the recommended range.

When possible, drug levels should be monitored to avoid toxicity or subtherapeutic dosing. This is particularly important for levels of antibiotics that have a narrow therapeutic index, such as aminoglycosides, with heightened concern in patients with a reduced GFR.

Antibiotic stewardship — Institutionalization is a major risk factor for disease due to antibiotic-resistant organisms. Methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), fluoroquinolone-resistant Streptococcus pneumoniae, and multiply-resistant Gram-negative bacilli are more frequent causes of infection among institutionalized older patients than those who are community-dwelling [11,12,37]. Additionally, patients with indwelling devices are at particularly high risk [13,14].

Antibiotic resistance is fostered in the nursing home setting by debilitated hosts, close proximity of residents, and persistent antibiotic pressure. Over 50 percent of older adults in nursing homes carry a drug-resistant organism [38]. Major strategies to enhance antimicrobial stewardship in nursing homes include: avoiding treatment of asymptomatic bacteriuria, specifically addressing avoidance of antibiotics in end-of-life discussions, and focusing on the shortest effective duration of therapy for specific syndromes [16,39-41]. The Centers for Disease Control and Prevention (CDC) has described 10 core elements of antimicrobial stewardship which include leadership support, accountability, drug expertise, a plan of action, monitoring, reporting, and education. Infection control in long-term care facilities is discussed in detail elsewhere. (See "Principles of infection control in long-term care facilities".)

SPECIFIC INFECTIOUS SYNDROMES — The following section will review major differences in the causative agents, evaluation, management, and prevention of a variety of common infectious syndromes in older adults. This review will not attempt to review all infections affecting older adults. Multiple topics in UpToDate address issues related to these and other infections.

Urinary tract infection — Urinary tract infection (UTI) is the most common infectious illness in adults age 65 and over, and in general it is diagnosed and managed in the same way as in the general population [42,43]. However, establishing the diagnosis in older patients is complicated due to the higher prevalence of chronic urinary symptoms and cognitive impairment, which make it difficult to identify specific UTI symptoms. Further, there is a high prevalence of asymptomatic bacteriuria in this population, which often leads to overdiagnosis and unnecessary treatment [44].

We recommend urine testing only in the presence of classic signs and symptoms of UTI (acute dysuria, new or worsening urgency or frequency, new incontinence, gross hematuria, and suprapubic or costovertebral angle tenderness) or physiologic signs of serious acute illness (eg, fever, other major vital sign abnormalities, changes in level of consciousness). Signs of systemic infection, particularly in the absence of urinary symptoms, should prompt evaluation for other sources of infection.

Restricting urine testing for these clinical features is particularly challenging in certain populations:

●Patients with chronic lower urinary tract symptoms – It can sometimes be difficult to tease out new symptoms in patients who have chronic incontinence, frequency, or urgency. It is important for the clinician to have a good understanding of the patient’s usual symptoms in order to detect any meaningful and persistent changes. For example, in a woman with chronic incontinence, new onset of dysuria or gross hematuria would be an appropriate trigger for urine testing.

●Patients with nonspecific symptoms (such as mental status changes) – Many clinicians consider nonspecific symptoms such as functional decline and behavioral or mental status changes as indicative of a UTI in older patients [45]. Too often, "checking a urinalysis and culture" is a reflex that does not take into account the consequence of potentially unnecessary antibiotics. Although older adults may present with atypical signs and symptoms, most older adults with an infection will also present with some localizing signs and symptoms [20]. We do not check urine testing based on such nonspecific symptoms in the absence of findings concerning for systemic infection as above. Growing evidence indicates that these nonspecific features are not reliable predictors of bacteriuria or UTI [46-49], and there is no evidence that treating bacteriuria in patients with delirium, falls, or confusion improves outcomes [50,51]. Furthermore, patients with dementia have normal fluctuations in behavior, and because of the frequency of asymptomatic bacteriuria in this population, urine testing will often yield a positive culture; this can erroneously link such normal fluctuations with bacteriuria, resulting in repeated unnecessary antibiotic treatment and subsequent development of resistant organisms. Urinary tract symptoms are difficult to elicit in patients with cognitive impairment; in such cases, clinical suspicion for UTI often rests on the emergence of new symptoms as noted by clinicians who know the patient well.

Other criteria have been proposed to clarify the symptoms that warrant testing and potential treatment for a presumptive UTI in residents of long-term care facilities (table 1) [52]. Clinical algorithms using such criteria have been shown to decrease antibiotic prescriptions for suspected UTI in nursing home settings [53].

Being judicious about urine testing is important in these populations because neither positive urinalyses nor culture results necessarily indicate a true infection. Urinalysis results have low specificity for UTI. Although they can be used to rule out UTI in those with a low pre-test probability, the presence of positive leukocyte esterase or nitrite on dipstick does not rule in a UTI. (See "Sampling and evaluation of voided urine in the diagnosis of urinary tract infection in adults", section on 'Accuracy'.)

Furthermore, the presence of bacteria on culture does not equate to a UTI. The urinary tract is increasingly recognized as a non-sterile environment with a generally beneficial microbiome, which may provide protection against infection, and for which treatment with antibiotics may be harmful [54,55]. Asymptomatic bacteriuria occurs in up to 6 to 16 percent of older women in the community and 25 to 54 percent of women in nursing homes, with a frequency in men about half those figures [56]. With the use of chronic catheters, rates are even higher (about 85 percent for condom catheters and nearly 100 percent for indwelling catheters).

Diagnosis of UTI is discussed in detail elsewhere. (See "Acute simple cystitis in adult and adolescent females", section on 'Diagnosis' and "Acute complicated urinary tract infection (including pyelonephritis) in adults and adolescents", section on 'Diagnosis'.)

When the diagnosis of UTI is in doubt (eg, pyuria and bacteriuria in the setting of ambivalent symptoms), a reasonable management strategy in patients who do not appear seriously ill is to defer antibiotic treatment for one week with follow-up [43], since 25 to 50 percent of older women with UTI symptoms will improve without therapy in this time frame [57]. Although a large retrospective database analysis of patients ≥65 years of age with lower UTI suggested an association between delaying antimicrobial therapy and subsequent bloodstream infection within 60 days, multiple limitations of this study reduce confidence in the findings [58]. Furthermore, in a subsequent analysis of the same dataset by different researchers, delayed antibiotic therapy was not associated with subsequent bloodstream infections [59]. However, this analyses did find evidence of some increase in mortality in the delayed therapy group. These discordant findings could be explained by residual confounding and suggest that more research is warranted to further guide practice.

We recommend against antibiotic "trials" as these may cause drug toxicity, drug-drug interactions, and antimicrobial resistance. Numerous studies suggest that there is no clinical benefit to treatment of asymptomatic bacteriuria and that such treatment can lead to significant side effects, expense, and potential for selection of resistant organisms. (See "Asymptomatic bacteriuria in adults".)

For patients diagnosed with UTI, the management is the same as in the general population and depends on whether the infection is thought to be primarily in the bladder (ie, simple cystitis) or whether the UTI is complicated by upper tract (pyelonephritis), prostatic, or systemic involvement. Escherichia coli, Klebsiella pneumoniae, and Enterococcus faecalis are implicated in the majority of UTIs in older adults [60]. The approach to management of cystitis and complicated UTI is discussed in detail elsewhere. (See "Acute simple cystitis in adult and adolescent females" and "Acute simple cystitis in adult and adolescent males" and "Acute complicated urinary tract infection (including pyelonephritis) in adults and adolescents".)

The management of catheter-associated UTI is discussed elsewhere. (See "Catheter-associated urinary tract infection in adults".)

The use of topical estrogen in postmenopausal women for prevention of recurrent cystitis is discussed elsewhere. (See "Recurrent simple cystitis in women".)

Pneumonia — The incidence of pneumonia and its associated mortality both increase with age and thus pneumonia is a common and serious condition in patients 65 years and older [61-64]. The approach to diagnosis and management of pneumonia in older adults is the same as in the general population and is discussed elsewhere. (See "Clinical evaluation and diagnostic testing for community-acquired pneumonia in adults" and "Treatment of community-acquired pneumonia in adults in the outpatient setting".)

Because of the association between pneumonia-related mortality and older age, age is a component of prognostic formulas to assess severity and determine indications for hospitalization. However, these formulas are intended to supplement rather than override the judgment of the clinicians. For older adults, other issues that are important to the decision to hospitalize include social support, ability to take oral medicines, living conditions, underlying psychiatric issues, cognitive impairment, or functional impairment.

The microbiology of pneumonia in older adults differs from that of young adults. Streptococcus pneumoniae is still the predominant organism, but polymicrobial infection and Gram-negative organisms (Haemophilus influenzae, Legionella pneumophila, Moraxella catarrhalis, Klebsiella spp) occur more commonly, particularly in patients with chronic obstructive pulmonary disease or among those who reside in long-term care facilities [65,66].

Antibiotic treatment for pneumonia in older adults follows standard guidelines. However, the risk of methicillin-resistant S. aureus (MRSA) and Gram-negative organisms should be taken into account for patients who reside in nursing homes. (See "Treatment of community-acquired pneumonia in adults in the outpatient setting" and "Treatment of community-acquired pneumonia in adults who require hospitalization" and "Treatment of hospital-acquired and ventilator-associated pneumonia in adults".)

Immunization for influenza and pneumococcus are the most important pneumonia preventive strategies. While pneumococcal vaccination may not prevent pneumonia in older adults, rates of bacteremia and invasive pneumococcal disease are decreased in immunized patients, and mortality in older patients hospitalized with pneumonia is lower among those who were vaccinated prior to admission [67,68]. (See "Pneumococcal vaccination in adults" and "Seasonal influenza vaccination in adults".)

Older adults are at higher risk for aspiration pneumonia. A number of interventions (eg, positioning, dietary changes, drugs, oral hygiene, oral rinse solutions, tube feeding) have been proposed to prevent aspiration with limited data to document effectiveness [69-75]. Discontinuation of proton pump inhibitors is also a preventive strategy [76]. Other techniques for the prevention and treatment of aspiration in hospitalized patients are discussed separately. (See "Aspiration pneumonia in adults".)

Influenza epidemics disproportionately affect older adults, with higher rates of morbidity and mortality [77-80], the treatment of which is discussed elsewhere. (See "Seasonal influenza in nonpregnant adults: Treatment".)

Reactivation tuberculosis is also more common in older adults since they are more likely to have been exposed to Mycobacterium tuberculosis in the first half of the 20^th century. Treatment is discussed elsewhere. (See "Treatment of tuberculosis infection (latent tuberculosis) in nonpregnant adults without HIV infection".)

Bacteremia — When compared with young adults, the presentation of bacteremia may be more subtle in older patients, with a lower likelihood of chills, sweating or fever. Thus, it may be appropriate to order blood cultures without these signs and symptoms but when sepsis is suspected, such as in the setting of tachycardia or hypotension [25].

Gastrointestinal and genitourinary sources of bacteremia are more common in older adults, as is isolation of Gram-negative rods, a trend that continues to increase throughout the eighth and ninth decades of life [81].

Bacteremia carries a poorer prognosis with advanced age. For example, nosocomial Gram-negative bacteremia has a mortality rate of 5 to 35 percent in young adults and 37 to 50 percent in older adults [82]. Nosocomial bacteremia in older adults is highly associated with the presence of invasive devices such as intravenous or urinary catheters and is most commonly due to MRSA [83].

The treatment of bacteremia is discussed in detail elsewhere. (See "Gram-negative bacillary bacteremia in adults" and "Clinical approach to Staphylococcus aureus bacteremia in adults".)

Fever of unknown origin — Fever of unknown origin (FUO) is defined as temperature >38.3°C (101°F) for at least three weeks and undiagnosed after one week of medical evaluation.

The causes of FUO in older patients differ somewhat from those in younger adults. In particular, giant cell (temporal) arteritis and polymyalgia rheumatica are important considerations in older patients, and patients age >60 years with FUO should have a rheumatological evaluation including early temporal artery biopsy, particularly if the erythrocyte sedimentation rate or liver enzymes are elevated [84]. (See "Diagnosis of giant cell arteritis".)

In the absence of specific risk factors, older adults in resource-rich settings are more likely to have been exposed to M. tuberculosis, which was more prevalent in the first half of the 20^th century. (See "Fever of unknown origin in adults: Etiologies", section on 'Infections'.)

Although the prevalence of malignancies increase with age, malignant disease as a cause of FUO occurs with similar frequency in old and young adults [85,86]. In both age groups, non-Hodgkin lymphoma accounts for the majority of such cases. (See "Fever of unknown origin in adults: Etiologies", section on 'Malignancies'.)

Infective endocarditis — Infective endocarditis (IE) is often related to degenerative valvular disease, mitral valve prolapse, or a prosthetic valve [87]. Older adults have a fivefold higher risk of IE than the general population [88]. A low threshold for suspecting IE and for pursuing transesophageal echocardiography (TEE) if transthoracic echocardiography (TTE) is negative is warranted.

The diagnosis of IE may be more difficult in older patients and is often delayed due to atypical clinical presentations and difficulty in interpreting echocardiographic findings. Certain classic signs and symptoms of IE such as fever, leukocytosis, embolic events, splenomegaly, skin lesions (Osler nodes, Janeway lesions), and conjunctival hemorrhages are less common with advanced age [89].

Several features of IE in older adults complicate the use of echocardiography. The higher prevalence of calcified valvular lesions and prosthetic valves makes echocardiographic findings more difficult to interpret in older adults, particularly when using TTE [90]. In addition, older adults tend to have smaller and fewer vegetations than younger adults and a higher rate of intracardiac abscess and prosthetic perivalvular complications [89].

For these reasons, it is recommended that a lower threshold for obtaining TEE be employed in older adult patients suspected of having IE. However, it is important to be aware of the potential risks of the procedure in older adults. Intravenous sedation or general anesthesia is often used when performing TEE, which increase the risk of delirium and agitation in older patients with cognitive impairment, polypharmacy, or multiple comorbidities. (See "Clinical manifestations and evaluation of adults with suspected left-sided native valve endocarditis".)

Streptococci and staphylococci are recovered from approximately 80 percent of older adults with IE [87], although enterococcal and Gram-negative organisms occur more commonly than in younger patients, likely due to a greater incidence of gastrointestinal and genitourinary sources of bacteremia. Antimicrobial treatment of infective endocarditis is discussed elsewhere. (See "Antimicrobial therapy of left-sided native valve endocarditis" and "Antimicrobial therapy of prosthetic valve endocarditis".)

HIV infection — Because HIV has primarily afflicted younger adults (in their 20s and 30s), most of the HIV literature defines “older adults” as those age 50 years or over. The success of antiretroviral therapy (ART) has resulted in the long-term survival of many patients with HIV, increasing the number of older adults with this chronic infection. In general, the same recommendations on management of HIV infection in adults and adolescents apply to older adults as well. However, specific considerations in older adults include under-diagnosis of HIV infection, issues of drug interactions with antiretroviral agents, and age-related comorbid conditions. These are discussed in greater detail elsewhere. (See "HIV infection in older adults".)

Prosthetic device infections — The prevalence of implanted prosthetic devices (eg, prosthetic joints, cardiac pacemakers, artificial heart valves, vascular grafts) increases with advancing age. A two-stage procedure with device removal, prolonged antibiotic administration, and subsequent reimplantation of the device is usually considered the gold standard of therapy. However, in older adults, the goals of treatment and the importance of maximizing functional status may affect treatment choice. For example, long periods of debility and being bed-bound are more likely to result in loss of functional status and independence in older adults, and these outcomes are rarely considered in most trials that evaluate cure rates or survival as the primary endpoint of interest. Functional assessment should be the focus of subsequent clinical trials in older adults [91]. General treatment recommendations for prosthetic joint infections are discussed separately. (See "Prosthetic joint infection: Treatment".)

COVID-19 — Although persons of all ages can acquire severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, older adults are at increased risk of morbidity and mortality. The epidemiology and clinical characteristics of coronavirus disease 2019 (COVID-19), including the impact of older age, are discussed elsewhere. (See "COVID-19: Clinical features" and "COVID-19: Diagnosis" and "COVID-19: Clinical features", section on 'Increasing age'.)

COVID-19 is a respiratory tract illness that commonly causes fever, cough, fatigue, anorexia, shortness of breath, myalgias, sore throat, headache, chills, and new loss of taste or smell [92,93]. Early reports suggest that shortness of breath is perhaps more frequent among older adults (12 percent for patients >60 years versus 3 percent for patients <60 years) [94]. Much like other infections, the fever response may be blunted, and the classic symptoms of dyspnea and cough may not be robust [95]. Similar to other infections, older adults with COVID-19 may present with subtle or nonspecific findings [96] Asymptomatic infection is also common [97].

In the appropriate clinical settings (community spread or proximity to known cases), clinicians should have a low threshold for considering COVID-19 in older adults with nonspecific symptoms such as falls, confusion or worsening functional impairment [98]. It is important to recognize the full spectrum of these findings in older adults in order to prevent COVID-19 transmission from asymptomatic or presymptomatic individuals.

A large number of COVID-19 infections and deaths have occurred in nursing homes. Partnerships between hospitals are nursing homes are important to help mitigate spread of the virus [99,100]. Management of patients with COVID-19 in nursing homes is discussed separately. (See "COVID-19: Management in nursing homes".)

Treatment for older adults is the same as for younger patients and is discussed separately. (See "COVID-19: Management in hospitalized adults" and "COVID-19: Management of the intubated adult" and "COVID-19: Management of adults with acute illness in the outpatient setting".)

In hospitalized patients, or those with severe illness, a thoughtful discussion of advance care planning under the guidance of palliative care or ethics teams (if needed) is appropriate, due to the poor prognosis associated with severe infection in older adults. In older adults hospitalized with COVID-19, delirium is associated with greater risk of in-hospital mortality [101]. (See "Advance care planning and advance directives" and "Advance care planning and advance directives", section on 'COVID-19 resources'.)

Resources are available to help clinicians who are caring for patients in isolation at the end of life. These are discussed separately. (See "Palliative care: The last hours and days of life", section on 'COVID-19 communication resources'.)

IMMUNIZATIONS — Immunization schedules for adults in good health (figure 1) and those with chronic medical conditions (figure 2) are discussed elsewhere. (See "Standard immunizations for nonpregnant adults".)

Vaccines for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are discussed separately. (See "COVID-19: Vaccines".)

TRAVEL CONSIDERATIONS FOR OLDER ADULTS — Older adults are among the most widely traveled members of society. In general, immunization strategies and travel advice are the same as for younger adults. (See "Travel advice" and "Immunizations for travel".)

However, some live-attenuated organism vaccines may be harmful in some older individuals and should only be given when the risk is high and there is no alternative [102]. The best-studied of these is yellow fever vaccine. Death and hospitalization following yellow fever vaccination are 3.5 times more likely in those aged 65 to 74 years and nine times more likely in those >75 years compared with younger individuals [103]. (See "Yellow fever: Treatment and prevention", section on 'Whom to vaccinate'.)    

Chemoprophylaxis for malaria may be challenging in older persons, particularly those with heart disease due to side effects of certain agents (eg, mefloquine may produce dizziness, change in mental status, and bradycardia or prolonged QT intervals). There are many alternative regimens for malaria prophylaxis, but familiarity with current resistance patterns is essential and should guide one’s choice for chemoprophylaxis. Clinicians are referred to the Centers for Disease Control and Prevention (CDC) website for the latest recommendations based on geography and local resistance patterns. (See "Prevention of malaria infection in travelers".)

The primary treatment for traveler’s diarrhea is replenishment of fluids and electrolytes. Indications for antibiotic treatment or use of antimotility agents are the same as for younger adults and are discussed in detail elsewhere. (See "Travelers' diarrhea: Epidemiology, microbiology, clinical manifestations, and diagnosis" and "Travelers' diarrhea: Treatment and prevention".)

SUMMARY AND RECOMMENDATIONS

●Increased risk – Older adults are at greater infection risk due to immune senescence, comorbidities, and communal residence. (See 'Increased risk for infection' above.)

●Clinical findings – Typical signs or symptoms of infection, including fever, may be absent in older adults. In frail older adults, we have a lower threshold for fever. Furthermore, nonspecific symptoms such as increased confusion, falling, and anorexia are common manifestations of infection which may appropriately lead to further evaluation for infection, including diagnostic testing. However, empiric antibiotics, if started, should be discontinued if diagnostic tests are negative. (See 'Suspicion for infection' above and 'Fever definition' above.)

●Antibiotic management – Antibiotic dosing should take into account reduced renal function with aging. However, it is important that older adults with serious infection receive the appropriate therapeutic dose. Institutionalized older adults are at increased risk for antibiotic resistance, particularly those with indwelling devices (bladder or vascular catheters, gastrostomy tubes, etc), and this risk should inform empiric antibiotic selection. (See 'Antibiotic management' above.)

●Challenging diagnosis of urinary tract infection – Urinary tract infection (UTI) is common in older adults, and in general it is managed in the same way as in the general population. However, the diagnosis is complicated by the higher prevalence of chronic urinary symptoms, cognitive impairment, and asymptomatic bacteriuria. Therefore, is important to have a high threshold for urine testing to avoid overtreatment (table 1). (See 'Urinary tract infection' above.)

●Infective endocarditis – Older adults are at increased risk for infective endocarditis (IE), with most infections due to streptococci or staphylococci. Valvular vegetations may be even more difficult to detect with transthoracic echocardiogram (TTE) than in younger individuals, and so we have a lower threshold to proceed to transesophageal echocardiography (TEE). (See 'Infective endocarditis' above.)

●COVID-19 – Older adults are at increased risk of morbidity and mortality from COVID-19. (See 'COVID-19' above.)