Pneumonia and Pandemic Influenza A H1N1 Virus Infection: A Review of the Literature

Servet Kayhan, Halit Çınarka, Aziz Gümüş, Ünal Şahin


Influenza viruses cause seasonal epidemics and occasional pandemics. On 18 March 2009, A novel swine origin influenza A (H1N1) virus was seen in Mexico, then a global outbreak of respiratory illness started. The new H1N1 virus usually attaches to tracheobronchial epithelial cells and the clinical picture ranges from transient lower respiratory tract infections to severe pneumonia leading to acute respiratory distress syndrome. The main complication is extension of viral infection to the alveoli that causes primary viral pneumonia. The most common radiologic findings are unilateral or bilateral ground-glass opacities and multifocal areas of consolidations Bacterial coinfections, particularly Streptococcus pneumoniae and Staphylococcus aureus, increase the severity of illness. Patients with underlying cardiopulmonary comorbid conditions, pregnancy and obesity appear to be at higher risk of severe pneumonia. The severe cases have required admission to intensive care units and needs to mechanical ventilation. H1N1 influenza virus is now in post-pandemic period; however, localized outbreaks of various magnitudes are being reported.

Keywords: H1N1; influenza; pandemic; pneumonia


Full Text:



Chowell G, Bertozzi SM, Colchero MA, Lopez-Gatell H, Alpuche-Aranda C, Hernandez M, Miller MA. Severe respiratory disease concurrent with the circulation of H1N1 influenza. N Engl J Med. 2009;361(7):674-679. doi:10.1056/NEJMoa0904023.

World Health Organization (WHO), 2009. Outbreak of swine origin influenza A (H1N1) virus infection-Mexico, March-April 2009. http//, MMWR Morb Mortal Wkly Rep. 58, 467. September 2011.

Combes A, Pellegrino V. Extracorporeal membrane oxygenation for 2009 influenza A (H1N1)-associated acute respiratory distress syndrome. Semin Respir Crit Care Med. 2011;32(2):188-194.

Centers for Disease Control and Prevention (CDC). Bacterial coinfections in lung tissue specimens from fatal cases of 2009 pandemic influenza A (H1N1) – United States, May–August 2009. MMWR Morb Mortal Wkly Rep 2009; 58: 1071–1074.

Gong MN, Bajwa E, Thompson BT, Christiani DC. Body mass index is associated with the development of acute respiratory distress syndrome. Thorax 2010;65:44-50.

Li M, Zhu JB, Chen GQ, Yang WY, Tao C, Wang XH. Influenza A (H1N1) pneumonia: an analysis of 63 cases by chest CT. Chin Med J (Engl). 2011;124(17):2669-2673.

Valente T, Lassandro F, Marino M, Squillante F, Aliperta M, Muto R. H1N1 pneumonia: our experience in 50 patients with a severe clinical course of novel swine-origin influenza A (H1N1) virus (S-OIV). Radiol Med. 2012;117(2):165-184. doi: 10.1007/s11547-011-0734-1.

Riquelme R, Torres A, Rioseco ML, et al. Influenza pneumonia: a comparison between seasonal influenza virus and the H1N1 pandemic. Eur Respir J. 2011;38:106–111.

Chan PA, Mermel LA, Andrea SB, McCulloh R, Mills JP, Echenique I, et al. Distinguishing characteristics between pandemic 2009-2010 influenza A (H1N1) and other viruses in patients hospitalized with respiratory illness. PLoS One. 2011;6(9):e24734. doi: 10.1371/journal.pone.0024734.

Fabbiani M, Sali M, Di Cristo V, Pignataro G, Prete V, Farina S, et al. Prospective evaluation of epidemiological, clinical, and microbiological features of pandemic influenza A (H1N1) virus infection in Italy. J Med Virol. 2011;83(12):2057-2065. doi: 10.1002/jmv.22231.

Dhanoa A, Fang NC, Hassan SS, Kaniappan P, Rajasekaram G. Epidemiology and clinical characteristics of hospitalized patients with pandemic influenza A (H1N1) 2009 infections: the effects of bacterial coinfection. Virol J. 2011;8:501. doi: 10.1186/1743-422X-8-501.

Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team, Dawood FS, Jain S, Finelli L, Shaw MW, Lindstrom S, Garten RJ, Gubareva LV, Xu X, Bridges CB, Uyeki TM: Emergence of a novel swine-origin influenza A (H1N1) virus in humans. N Engl J Med 2009, 360:2605-2615.

Djibre M, Berkane N, Salengro A, Ferrand E, Denis M, Chalumeau-Lemoine L, et al. Non-invasive management of acute respiratory distress syndrome related to Influenza A (H1N1) virus pneumonia in a pregnant woman. Intensive Care Med. 2010;36(2):373-374. doi: 10.1007/s00134-009-1684-0.

Marcos MA, Esperatti M, Torres A. Viral pneumonia. Curr Opin Infect Dis. 2009;22:143–147.

Nicolini A., Cilloniz C., Cuenca E., Torres A. Influenza A (H1N1) Pneumonia: A Review and Update. Clinical Pulmonary Medicine, 2012;19(6), 246-253.

Cunha BA. Swine influenza (H1N1) pneumonia: clinical considerations. Infect Dis Clin North Am. 2010;24:203–228.

Lat A, Bhadelia N, Miko B, Furuya EY, Thompson GR 3rd. Invasive aspergillosis

after pandemic (H1N1) 2009. Emerg Infect Dis. 2010;16(6):971-973. doi: 10.3201/eid1606.100165.

Cunha BA, Syed U, Strollo S. Non-specific laboratory test indicators of severity in hospitalized adults with swine influenza (H1N1) pneumonia. Eur J Clin Microbiol Infect Dis. 2010;29:1583–1588.

Cunha BA, Pherez FM, Schoch P. Diagnostic importance of relative lymphopenia as a marker of swine influenza (H1N1) in adults. Clin Infect Dis. 2009;49:1454–1456.

Dye JA, Adler KB. Effects of cigarette smoke on epithelial cells of the respiratory tract. Thorax 1994, 49:825-834.

Puchelle E, Zahm JM, Bertrand A. Influence of age on bronchial mucociliary transport. Scand J Respir Dis 1979;60:307-313.

Bender BS, Small PA Jr. Influenza: pathogenesis and host defense. Semin Respir Infect 1992;7:38-45.

Treanor JJ. Influenza virus. In Principles and Practice of Infectious Disease. Vol. 2. Edited by Mandell G, Bennett JE, Dolin R. Philadelphia, PA: Churchill Livingstone; 2005:2060.

Walsh JJ, Dietlein LF, Low FN, Burch GE, Mogabgab WJ. Bronchotracheal response in human influenza. Type A, Asian strain, as studied by light and electron microscopic examination of bronchoscopic biopsies. Arch Intern Med 1961, 108: 376-388.

Oseasohn R, Adelson L, Kaji M. Clinicopathologic study of thirty-three fatal cases of Asian influenza. N Engl J Med 1959, 260:509-518.

Louria DB, Blumenfeld HL, Ellis JT, Kilbourne ED, Rogers DE. Studies on influenza in the pandemic of 1957-1958. II. Pulmonary complications of influenza. J Clin Invest 1959, 38(1Part 2):213-265.

Capelozzi VL, Parra ER, Ximenes M, Bammann RH, Barbas CS, Duarte MI. Pathological and ultrastructural analysis of surgical lung biopsies in patients with swine-origin influenza type A/H1N1 and acute respiratory failure. Clinics (Sao Paulo). 2010;65(12):1229-1237.

Bai L, Cao B, Wang C. Influenza A pandemic (H1N1) 2009 virus infection. Chin Med J (Engl). 2011;124:3399–3402.

Yamada K, Shinmoto H, Hamamoto M, Yoshida Y, Kawauchi T, Kaji T, et al. Pneumonia induced by swine-origin influenza A (H1N1) infection: chest computed tomography findings in children. Jpn J Radiol. 2011 Dec;29(10):712-717. doi: 10.1007/s11604-011-0620-8.

Shaham D, Bogot NR, Aviram G, Guralnik L, Lieberman S, Copel L, et al. Severe influenza A (H1N1): the course of imaging findings. Isr Med Assoc J. 2011;13(10):591-596.

Perez-Padilla R, de la Rosa-Zamboni D, Ponce de Leon S, Hernandez M, Quinones-Falconi F, Bautista E, et al. Pneumonia and respiratory failure from swine-origin influenza A (H1N1) in Mexico. N Engl J Med. 2009;361(7):680-689.

Aviram G, Bar-Shai A, Sosna J, Rogowski O, Rosen G, Weinstein I, Steinvil A, Zimmerman O. H1N1 influenza: initial chest radiographic findings in helping predict patient outcome. Radiology. 2010 ;255(1):252-259. doi:10.1148/radiol.10092240.

Marcos MA, Ramon S, Anton A, Martinez E, Vilella A, Olive V, et al. Clinical relevance of mixed respiratory viral infections in adults with influenza A H1N1. Eur Respir J. 2011;38(3):739-742. doi: 10.1183/09031936.00168610.

Nisii C, Meschi S, Selleri M, Bordi L, Castilletti C, Valli MB, et al. Frequency of detection of upper respiratory tract viruses in patients tested for pandemic H1N1/09 viral infection. J Clin Microbiol. 2010;48(9):3383-3385. doi:10.1128/JCM.01179-10.

Renois F, Talmud D, Huguenin A, Moutte L, Strady C, Cousson J, et al. Rapid detection of respiratory tract viral infections and coinfections in patients with influenza-like illnesses by use of reverse transcription-PCR DNA microarray systems. J Clin Microbiol. 2010;48(11):3836-3842. doi: 10.1128/JCM.00733-10.

Viasus D, Pano-Pardo JR, Pachon J, Campins A, Lopez-Medrano F, Villoslada A, et al. Novel Influenza A (H1N1) Study Group of the Spanish Network for Research in Infectious Diseases (REIPI). Factors associated with severe disease in hospitalized adults with pandemic (H1N1) 2009 in Spain. Clin Microbiol Infect. 2011;17(5):738-46. doi: 10.1111/j.1469-0691.2010.03362

Koon K, Sanders CM, Green J, Malone L, White H, Zayas D, et al. Co-detection of pandemic (H1N1) 2009 virus and other respiratory pathogens. Emerg Infect Dis. 2010;16(12):1976-1978. doi: 10.3201/eid1612.091697.

Hayashi Y, Vaska VL, Baba H, Nimmo GR, Davis L, Paterson DL. Influenza-associated bacterial pathogens in patients with 2009 influenza A (H1N1) infection: impact of community-associated methicillin-resistant Staphylococcus aureus in Queensland, Australia. Intern Med J. 2012;42(7):755-760. doi: 10.1111/j.1445-5994.2011.02602.x.

Murray RJ, Robinson JO, White JN, Hughes F, Coombs GW, Pearson JC, et al. Community-acquired pneumonia due to pandemic A(H1N1)2009 influenzavirus and methicillin resistant Staphylococcus aureus co-infection. PLoS One. 2010;5(1):e8705. doi: 10.1371/journal.pone.0008705.

Rello J, Rodriguez A, Ibanez P, Socias L, Cebrian J, Marques A, et al. H1N1 SEMICYUC Working Group. Intensive care adult patients with severe respiratory failure caused by Influenza A (H1N1)v in Spain. Crit Care. 2009;13(5):R148. doi: 10.1186/cc8044.

Miller RR 3rd, Markewitz BA, Rolfs RT, Brown SM, Dascomb KK, Grissom CK ,et al. Clinical findings and demographic factors associated with ICU admission in Utah due to novel 2009 influenza A(H1N1) infection. Chest. 2010 Apr;137(4):752-758. doi: 10.1378/chest.09-2517.

Riquelme R, Jimenez P, Videla AJ, Lopez H, Chalmers J, Singanayagam A, et al. Predicting mortality in hospitalized patients with 2009 H1N1 influenza pneumonia. Int J Tuberc Lung Dis. 2011;15(4):542-546. doi: 10.5588/ijtld.10.0539.

Kirakli C, Tatar D, Cimen P, Edipoglu O, Coskun M, Celikten E, et al. Survival from severe pandemic H1N1 in urban and rural Turkey: a case series. Respir Care. 2011;56(6):790–795.

Elbahlawan L, Gaur AH, Furman W, Jeha S, Woods T, Norris A, et al. Severe H1N1-associated acute respiratory failure in immunocompromised children. Pediatr Blood Cancer. 2011;57(4):625-628. doi: 10.1002/pbc.22973.

Louie JK, Acosta M, Winter K, Jean C, Gavali S, Schechter R, et al.; California Pandemic (H1N1) Working Group. Factors associated with death or hospitalization due to pandemic 2009 influenza A(H1N1) infection in California. JAMA. 2009;302(17):1896-1902. doi: 10.1001/jama.2009.1583.

Jain S, Kamimoto L, Bramley AM, Schmitz AM, Benoit SR, Louie J, et al. 2009 Pandemic Influenza A (H1N1) Virus Hospitalizations Investigation Team. Hospitalized patients with 2009 H1N1 influenza in the United States, April-June 2009. N Engl J Med. 2009;361(20):1935-1944. doi: 10.1056/NEJMoa0906695.

Martin-Loeches I, Díaz E, Vidaur L, Torres A, Laborda C, Granada R,et al. H1N1 SEMICYUC/REIPI/CIBERES Working group. Pandemic and post-pandemic influenza A (H1N1) infection in critically ill patients. Crit Care. 2011;15(6):R286. doi: 10.1186/cc10573.

US Centers for Disease Control and Prevention: Interim guidance on specimen collection, processing, and testing for patients with suspected swine-origin influenza A (H1N1) virus infection [].

Pollock NR, Duong S, Cheng A, Han LL, Smole S, Kirby JE. Ruling out novel H1N1 influenza virus infection with direct fluorescent antigen testing. Clin Infect Dis 2009, 49:e66-68.

Monto AS, Gravenstein S, Elliott M, Colopy M, Schweinle J. Clinical signs and symptoms predicting influenza infection. Arch Intern Med 2000, 160:3243-3247.

Hanshaoworakul W, Simmerman JM, Narueponjirakul U, Sanasuttipun W, Shinde V, Kaewchana S, et al. Severe human influenza infections in Thailand: oseltamivir treatment and risk factors for fatal outcome. PLoS One. 2009;4(6):e6051. doi: 10.1371/journal.pone.000605.

Boots RJ, Lipman J, Lassig-Smith M, Stephens DP, Thomas J, Shehabi Y,et al. Experience with high frequency oscillation ventilation during the 2009 H1N1 influenza pandemic in Australia and New Zealand. Anaesth Intensive Care. 2011;39(5):837-46.

Ramsey CD, Funk D, Miller RR 3rd, Kumar A. Ventilator management for hypoxemic respiratory failure attributable to H1N1 novel swine origin influenza virus. Crit Care Med. 2010 Apr;38(4 Suppl):e58-65. doi: 10.1097/CCM.0b013e3181cde600.

Hui DS, Lee N, Chan PK. Clinical management of pandemic 2009 influenza A (H1N1) infection. Chest. 2010;137:916–925.

Kaufman MA, Duke GJ, McGain F, French C, Aboltins C, Lane G, Gutteridge GA. Life-threatening respiratory failure from H1N1 influenza 09 (human swine influenza). Med J Aust. 2009;191(3):154-6.

Patel M, Dennis A, Flutter C, Khan Z. Pandemic (H1N1) 2009 influenza. Br J Anaesth. 2010 Feb;104(2):128-42. doi: 10.1093/bja/aep375.

Winck JC, Marinho A. Non-invasive ventilation in acute respiratory failure related to 2009 pandemic influenza A/H1N1 virus infection. Crit Care. 2010;104:128–142.

MacLaren G, Combes A, Bartlett RH. Contemporary extracorporeal membrane oxygenation for adult respiratory failure: life support in the new era. Intensive Care Med. 2012;38:210–220.

Australia and New Zealand Extracorporeal Membrane Oxygenation (ANZ ECMO) Influenza Investigators, Davies A, Jones D, Bailey M, Beca J, Bellomo R, Blackwell N, et al. Extracorporeal Membrane Oxygenation for 2009 Influenza A(H1N1) Acute Respiratory Distress Syndrome. JAMA. 2009 Nov 4;302(17):1888-95. doi: 10.1001/jama.2009.1535.

Noah MA, Peek GJ, Finney SJ, Griffiths MJ, Harrison DA, Grieve R, et al. Referral to an extracorporeal membrane oxygenation center and mortality among patients with severe 2009 influenza A(H1N1). JAMA. 201;306(15):1659-68. doi: 10.1001/jama.2011.1471.

World Health Organization. Available from: publications/infection_control/en/index.html. 04. p. 10-35 [In Greek].


  • There are currently no refbacks.

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.

2013-2023 (CC-BY) Australian International Academic Centre PTY.LTD.

Advances in Bioscience and Clinical Medicine