The study, published in the journal Radiology, also allowed the researchers to determine the difference between H7N9 pneumonia and other types of pneumonia.
The first case of the novel avian influenza A H7N9 virus was reported in China on March 30, 2013. It confirmed that the virus was initially transmitted to humans from chickens at a wet poultry market.
The H7N9 virus strain in humans causes severe respiratory illness, respiratory distress syndrome, organ failure and even death.
The co-author of the study, Zhiyong Zhang, M.D., Ph.D., from the Department of Radiology at Shanghai Public Health Clinical Center and Shanghai Medical College of Fudan University in China, said that "the severity of these findings is associated with the severity of the clinical condition of the patients."
Dr. Zhang and his team analyzed the clinical data of 12 different patients diagnosed with the A H7N9 virus. All the patients were admitted to the Shanghai Public Health Clinical Center between April 3, 2013, and April 20, 2013.
Of the twelve patients, only one said they had chickens kept at home and four others reported having visited a farmer's market prior to any signs of illness. The rest of the patients said that they had not been exposed to any poultry prior to becoming infected.
The patients experienced the following symptoms:
- High fever - between 38℃ to 40℃ (100.4℉ to 104℉)
- Difficulty breathing
- White phlegm
- Severe cough
The time between the first imaging examinations and the onset of symptoms for chest X-rays was between one to six days and two to nine days for computed tomography (CT).
In addition, the researchers carried out follow up X-rays and CT scans.
The imaging findings revealed:
- 12 patients with a hazy area in the lungs with the appearance of ground glass
- 11 patients with regions of lung tissue filled with liquid
- 11 patients with air-filled bronchi made visible by swelling in adjacent tissues
- 11 patients with thickening of pulmonary connective tissue
Dr. Zhang said "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."
Despite a few similarities in the imaging characteristics of H7N9 to H1N1 and severe acute respiratory syndrome (SARS), H7N9 shows some very different features.
Dr. Zhang concluded:
"Both H1N1 pneumonia and SARS distribute more peripherally, with more changes in the spaces between tissues, and progress less rapidly than H7N9. In our study, the right lower lung was most likely to be involved, while there's no lobar predilection in findings of H5N1 influenza."
Written by Joseph Nordqvist