Clinical features of human influenza A (H5N1) infection in Vietnam: 2004-2006

Abstract

Background: The first cases of avian influenza A (H5N1) in humans in Vietnam were detected in early 2004, and Vietnam has reported the second highest number of cases globally.

Methods: We obtained retrospective clinical data through review of medical records for laboratory confirmed cases of influenza A (H5N1) infection diagnosed in Vietnam from January 2004 through December 2006. Standard data was abstracted regarding clinical and laboratory features, treatment, and outcome.

Results: Data were obtained for 67 (72%) of 93 cases diagnosed in Vietnam over the study period. Patients presented to the hospital after a median duration of illness of 6 days with fever (75%), cough (89%), and dyspnea (81%). Diarrhea and mucosal bleeding at presentation were more common in fatal than in nonfatal cases. Common findings were bilateral pulmonary infiltrates on chest radiograph (72%), lymphopenia (73%), and increased serum transaminase levels (aspartate aminotransferase, 69%; alanine aminotransferase, 61%). Twenty-six patients died (case fatality rate, 39%; 95% confidence interval, 27%-51%) and the most reliable predictor of a fatal outcome was the presence of both neutropenia and raised alanine aminotransferase level at admission, which correctly predicted 91% of deaths and 82% of survivals. The risk of death was higher among persons aged < or =16 years, compared with older persons (P < .001), and the risk of death was higher among patients who did not receive oseltamivir treatment (P = .048). The benefit of oseltamivir treatment remained after controlling for potential confounding by 1 measure of severity (odds ratio, 0.15; 95% confidence interval, 0.026-0.893; P = .034).

Conclusion: In cases of infection with Influenza A (H5N1), the presence of both neutropenia and raised serum transaminase levels predicts a poor outcome. Oseltamivir treatment shows benefit, but treatment with corticosteroids is associated with an increased risk of death.

Figure 1

Survival plot for cases involving patients aged ≤16 years (dashed line), compared with cases involving patients aged >16 years (solid line), by duration since onset of illness.

Figure 2

Survival plot for cases in which patients received oseltamivir (dashed line), compared with cases in which patients did not receive oseltamivir (solid line), by duration since onset of illness (censored at day 30, because all deaths had occurred by day 21 after illness onset).

Figure 3

Neutrophil count for fatal and nonfatal cases (n = 31), by duration since hospital admission, excluding 5 patients who were treated with granulocyte macrophage colony-stimulating factor.