Relationship between respiratory viral load and lung lesion severity: a study in 24 cases of pandemic H1N1 2009 influenza A pneumonia

Objective: To investigate the relationship between respiratory viral load and lung lesion severity of patients with pandemic H1N1 2009 influenza A pneumonia.

Study design: Cross-sectional observation study.

Methods: 24 consecutive H1N1 influenza patients with viral pneumonia (13 males, 11 females, mean age: 17.5 years) during their presentation to hospital were retrospectively analysed. Viral load were first measured on average 5.2 days after the onset of symptoms. The initial CT and viral load measurement was carried on the same day in 13 patients. The rest were carried out with a mean interval time of 1.5 days. All patients had viral load follow-up till turned negative. Thirteen patients had radiological follow-up.

Results: There was no significant correlation between the initial lung lesion severity and viral load (P=0.4). Both viral load and lung lesion severity decreased over time, being highest value at initial presentation. The patients had higher initial viral load or higher initial lung lesion severity tended to be slower in resolving. The lung lesion decreased at a slower rate than viral load.

Conclusions: While there was no correlation between the initial viral load and lung lesion severity, these two indices provide valuable information for epidemiological control.