High-resolution computed tomography findings of swine-origin influenza A (H1N1) virus (S-OIV) infection: comparison with scrub typhus.
BACKGROUND
Swine-origin influenza A (H1N1) virus (S-OIV) infection and scrub typhus, also known as tsutsugamushi disease can manifest as acute respiratory illnesses, particularly during the late fall or early winter, with similar radiographic findings, such as a predominance of ground-glass opacity (GGO).


OBJECTIVE
To differentiate S-OIV infection from scrub typhus using high-resolution computed tomography (HRCT).


METHODS
We retrospectively reviewed the HRCT findings of 14 patients with S-OIV infection and 10 patients with scrub typhus. We assessed the location, cross-sectional distribution, and the presence of a peribronchovascular distribution of GGO and consolidations on HRCT. We also assessed the presence of interlobular septal thickening, bronchial wall thickening, pneumothorax, pneumomediastinum, pleural effusion, and mediastinal or axillary lymph node enlargement.


RESULTS
Scrub typhus was more common than S-OIV in elderly patients (P < 0.001). The monthly incidences of S-OIV and scrub typhus infection reached a peak between October and November. About 86% of S-OIV patients and 80% of scrub typhus patients presented with GGO. About 67% of the GGO lesions in S-OIV had a peribronchovascular distribution, but this was absent in scrub typhus (P = 0.005). Consolidation (93% vs. 10%, P < 0.001) and bronchial wall thickening (43% vs. 0%, P = 0.024) were more frequent in S-OIV infection than scrub typhus. Interlobular septal thickening (90% vs. 36%, P = 0.013) and axillary lymphadenopathy (90% vs. 0%, P < 0.001) were more common in scrub typhus than S-OIV infection.


CONCLUSIONS
There was considerable overlap in HRCT findings between S-OIV infection and scrub typhus. However, S-OIV showed a distinctive peribronchovascular distribution of GGO lesions. Consolidation and bronchial wall thickening were seen more frequently in S-OIV infection, whereas interlobular septal thickening and axillary lymphadenopathy were more common in scrub typhus. Thus, CT could be helpful for differential diagnosis between S-OIV infection and scrub typhus.
Department of Radiology, Hallym University College of Medicine, Seoul, Korea.
Bang Sil
BS
Jo
In Jae
IJ
Lee
Hyoung June
HJ
Im
Kwanseop
K
Lee
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D001365:Axilla; D001980:Bronchi; D002648:Child; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000000981:diagnostic imaging*; D008168:Lung / Q000000981:diagnostic imaging; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D008297:Male; D008478:Mediastinal Emphysema / Q000000981:diagnostic imaging; D008482:Mediastinum / Q000000981:diagnostic imaging; D008875:Middle Aged; D015588:Observer Variation; D010996:Pleural Effusion / Q000000981:diagnostic imaging; D011030:Pneumothorax / Q000000981:diagnostic imaging; D013902:Radiography, Thoracic / Q000379:methods*; D012137:Respiratory System / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D012612:Scrub Typhus / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014132:Trachea / Q000000981:diagnostic imaging; D055815:Young Adult