H1N1 influenza is a strain of influenza that notably resulted in a pandemic in 2009.
It is caused by a type of influenza A virus of swine origin.
There can be a wide spectrum of clinical syndromes ranging from being asymptomatic to fulminant viral pneumonia, respiratory failure and death.
Chest radiograph
It can have a variable presentation and a number of features have been described 2:
- initial chest radiographs usually show central or peripheral pulmonary ground-glass opacities (GGO) and consolidations that have a patchy or nodular appearance
- multizonal and bilateral peripheral opacities are associated with adverse prognosis
- it should be stressed that a normal radiograph cannot exclude a poor outcome
CT chest
Described imaging spectrum is broad, with each individual feature being non-specific on its own 2-3:
- 1. Agarwal PP, Cinti S, Kazerooni EA. Chest radiographic and CT findings in novel swine-origin influenza A (H1N1) virus (S-OIV) infection. AJR Am J Roentgenol. 2009;193 (6): 1488-93. doi:10.2214/AJR.09.3599 - Pubmed citation
- 2. Aviram G, Bar-Shai A, Sosna J et-al. H1N1 influenza: initial chest radiographic findings in helping predict patient outcome. Radiology. 2010;255 (1): 252-9. doi:10.1148/radiol.10092240 - Pubmed citation
- 3. Shim SS, Kim Y, Ryu YJ. Novel influenza A (H1N1) infection: chest CT findings from 21 cases in Seoul, Korea. Clin Radiol. 2011;66 (2): 118-24. doi:10.1016/j.crad.2010.07.011 - Pubmed citation
- 4. Elicker BM, Schwartz BS, Liu C et-al. Thoracic CT findings of novel influenza A (H1N1) infection in immunocompromised patients. Emerg Radiol. 2010;17 (4): 299-307. doi:10.1007/s10140-010-0859-x - Free text at pubmed - Pubmed citation
- 5. Ajlan AM, Quiney B, Nicolaou S et-al. Swine-origin influenza A (H1N1) viral infection: radiographic and CT findings. AJR Am J Roentgenol. 2009;193 (6): 1494-9. doi:10.2214/AJR.09.3625 - Pubmed citation
- 6. El-Badrawy A, Zeidan A, Ebrahim MA. 64 multidetector CT findings of influenza A (H1N1) virus in patients with hematologic malignancies. Acta Radiol. 2012;53 (6): 662-7. doi:10.1258/ar.2012.120038 - Pubmed citation
- 7. Choi MJ, Lee YS, Lee JY et-al. Novel influenza A (H1N1) virus infection in children: chest radiographic and CT evaluation. Korean J Radiol. 2010;11 (6): 656-64. doi:10.3348/kjr.2010.11.6.656 - Free text at pubmed - Pubmed citation
- 8. Lee EY, McAdam AJ, Chaudry G et-al. Swine-origin influenza a (H1N1) viral infection in children: initial chest radiographic findings. Radiology. 2010;254 (3): 934-41. doi:10.1148/radiol.09092083 - Pubmed citation
- 9. Edson Marchiori, Gláucia Zanetti, Giuseppe D'Ippolito, Carlos Gustavo Yuji Verrastro, Gustavo de Souza Portes Meirelles, Julia Capobianco, Rosana Souza Rodrigues. Swine-Origin Influenza A (H1N1) Viral Infection: Thoracic Findings on CT. (2012) American Journal of Roentgenology. 196 (6): W723-8. doi:10.2214/AJR.10.5109 - Pubmed