1. Jameson JL. Harrison’s principles of internal medicine. 20th ed. New York: McGraw-Hill;2018.
2. Yoon HK. Changes in the epidemiology and burden of community-acquired pneumonia in Korea. Korean J Intern Med. 2014; 29:735–7.
Article
3. Vital Statistics Division; Statistics Korea, Shin HY, Kim J, Lee S, Park MS, et al. Cause-of-death statistics in 2018 in the Republic of Korea. J Korean Med Assoc. 2020; 63:286–97.
Article
4. Musher DM, Roig IL, Cazares G, Stager CE, Logan N, Safar H. Can an etiologic agent be identified in adults who are hospitalized for community-acquired pneumonia: results of a one-year study. J Infect. 2013; 67:11–8.
Article
5. Wunderink RG, Waterer GW. Clinical practice: community-acquired pneumonia. N Engl J Med. 2014; 370:543–51.
6. Seki M, Kosai K, Yanagihara K, Higashiyama Y, Kurihara S, Izumikawa K, et al. Disease severity in patients with simultaneous influenza and bacterial pneumonia. Intern Med. 2007; 46:953–8.
Article
7. Kang YS, Ryoo SR, Byun SJ, Jeong YJ, Oh JY, Yoon YS. Antimicrobial resistance and clinical outcomes in nursing home-acquired pneumonia, compared to community-acquired pneumonia. Yonsei Med J. 2017; 58:180–6.
Article
8. Choi SH, Hong SB, Ko GB, Lee Y, Park HJ, Park SY, et al. Viral infection in patients with severe pneumonia requiring intensive care unit admission. Am J Respir Crit Care Med. 2012; 186:325–32.
Article
9. Jain S, Self WH, Wunderink RG, Fakhran S, Balk R, Bramley AM, et al. Community-acquired pneumonia requiring hospitalization among U.S. adults. N Engl J Med. 2015; 373:415–27.
Article
10. Chong YP, Jung KS, Lee KH, Kim MN, Moon SM, Park S, et al. The bacterial etiology of community-acquired pneumonia in Korea: a nationwide prospective multicenter study. Infect Chemother. 2010; 42:397–403.
Article
11. Yoo KH, Yoo CG, Kim SK, Jung JY, Lee MG, Uh ST, et al. Economic burden and epidemiology of pneumonia in Korean adults aged over 50 years. J Korean Med Sci. 2013; 28:888–95.
Article
12. Kim JE, Kim UJ, Kim HK, Cho SK, An JH, Kang SJ, et al. Predictors of viral pneumonia in patients with community-acquired pneumonia. PLoS One. 2014; 9:e114710.
Article
13. Hinojosa E, Boyd AR, Orihuela CJ. Age-associated inflammation and toll-like receptor dysfunction prime the lungs for pneumococcal pneumonia. J Infect Dis. 2009; 200:546–54.
Article
14. Kovacs EJ, Boe DM, Boule LA, Curtis BJ. Inflammaging and the lung. Clin Geriatr Med. 2017; 33:459–71.
Article
15. Liu L, Wei Q, Lin Q, Fang J, Wang H, Kwok H, et al. Anti-spike IgG causes severe acute lung injury by skewing macrophage responses during acute SARS-CoV infection. JCI Insight. 2019; 4:e123158.
Article
16. Ongradi J, Kovesdi V. Factors that may impact on immunosenescence: an appraisal. Immun Ageing. 2010; 7:7.
Article
17. Ron-Harel N, Notarangelo G, Ghergurovich JM, Paulo JA, Sage PT, Santos D, et al. Defective respiration and one-carbon metabolism contribute to impaired naive T cell activation in aged mice. Proc Natl Acad Sci U S A. 2018; 115:13347–52.
18. Salam N, Rane S, Das R, Faulkner M, Gund R, Kandpal U, et al. T cell ageing: effects of age on development, survival & function. Indian J Med Res. 2013; 138:595–608.