July 2, 2013 - H7N9
pneumonia is characterized by chest
x-ray and computed
tomography (CT) imaging findings that differentiate it from other types of
pneumonia, including rapidly progressive changes in the lungs and pulmonary connective
The results from a study
showed imaging characteristics are similar to those found in other respiratory
diseases, such as H1N1, H5N1, and severe acute respiratory syndrome (SARS),
there are differences.
H7N9 is a recently
discovered subtype of avian influenza virus or “bird flu.” In a recent study, Zhiyong
Zhang, MD, PhD, from the Department of Radiology at Shanghai Public Health
Clinical Center and Shanghai Medical College of Fudan University in China, and
colleagues evaluated the clinical data and radiologic files of 12 patients with
avian-origin influenza A H7N9 virus who were admitted to Shanghai Public Health
Clinical Center between April 3, 2013, and April 20, 2013. The 12 patients
included 9 men and 3 women, 47 to 81 years old (mean age, 66 years). All
patients exhibited fever with temperature of 38℃ to 40℃ (100.4℉ to 104℉), cough, shortness of breath, and white
phlegm, and loss of strength at the onset of the disease or within one week.
They rapidly progressed to severe pneumonia and acute respiratory distress
The intervals between
the onset of symptoms and the initial imaging examinations ranged from one to 6
days for chest
x-rays and 2 to 9 days for computed
tomography (CT). Every one or 2 days thereafter, doctors took chest
x-rays to monitor disease progression and treatment response. To evaluate
disease progression and possible complications, 10 of the patients underwent
follow-up CT 2 to 8 days after initial examination.
The imaging findings
opacity in all 12 patients, consolidations in 11 patients, air bronchograms
in11 patients, and interlobular septal thickening 11 patients. Lung lesions
involved 3 or more lobes in all cases, but were mostly detected in right lower
lobe. Follow-up CT in 10 patients showed interval improvement of the lesions in
3 patients and worsening of the lesions in 7 patients. Imaging findings closely
mirrored the overall clinical severity of the disease.
“The distribution and
very rapid progression of consolidations, ground-glass
opacity, and air bronchograms, with interstitial changes, in H7N9 pneumonia
help differentiate it from other causes of pneumonia,” Dr. Zhang said.
He added, “The severity
of these findings is associated with the severity of the clinical condition of
While these imaging
characteristics are similar to those found in other respiratory diseases, such
as H1N1, H5N1, and severe acute respiratory syndrome (SARS), there are
“Both H1N1 pneumonia and
SARS distribute more peripherally, with more changes in the spaces between
tissues, and progress less rapidly than H7N9,” Dr. Zhang said. “In our study,
the right lower lung was most likely to be involved, while there’s no lobar
predilection in findings of H5N1 influenza.”
Reference: Zhang, Wang Q, Shi Y, Jiang Y. Emerging H7N9 influenza a (novel reassortant
avian-origin) pneumonia. Radiology.
July 2, 2013.
For more information: www.rsna.org and www.appliedradiology.com