Objective: To evaluate the value of chest CT findings and dynamic changes of viral load in patients with novel influenza A (H1N1) infection in clinical diagnosis, differential diagnosis and treatment.
Methods: Fifty-one patients with confirmed novel influenza A (H1N1) according to the diagnostic criteria of the Ministry of Health, received chest X-ray, CT scans (HRCT) and viral load tests in our hospital from May to December of 2009. Based on whether there were signs of pneumonia in CT imaging, the patients were divided into a pneumonia group (n = 31) and a non-pneumonia group (n = 20). The relationship between chest CT changes and viral load was observed and analyzed statistically using SPSS 10.5 software.
Results: Patchy consolidations of lungs were the main findings in pneumonia group with influenza A (H1N1) infection, and ground-glass opacities were the main CT findings at acute and convalescent phases. Lobular and segmental shadows of the lungs were diffusely distributed, mostly found in lower lungs, especially the left lung. In some cases, the lung diseases were accompanied with mediastinal lymphadenopathy. Co-existence of pulmonary parenchymal, interstitial and pleural diseases was observed. Peak viral load occurred at the early phase of illness, with the mean initial viral load being 7.7 copies/ml and 4.2 copies/ml in the pneumonia and the non-pneumonia groups respectively. The viral nucleic acid became negative 4 days after antiviral treatment (course of 6 days). Dynamic observation of 3 patients with novel influenza A (H1N1) pneumonia showed that, the viral clearance period preceded the absorption of lung lesions in 2 cases, but viral clearance period of a young patient was significantly prolonged.
Conclusion: In patients with the novel influenza A (H1N1) infection, the viral load in the pneumonia group was significantly higher than that in the group with normal chest imaging. Dynamic observation on chest imaging and viral load may be beneficial for clinicians to start prompt and effective treatment.