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

Session V – Horby, Peter – Abstract 1 of 2

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

Author(s): Nguyen Thanh Liem1, MD PhD, Cao Viet Tung1, MD, Nguyen Duc Hien2, MD PhD, Tran Tinh Hien MD PhD3, Ngo Quy Chau4, MD PhD, Hoang Thuy Long5, MD PhD, Nguyen Tran Hien5 MD PhD, Le Quynh Mai5 MD PhD, Walter RJ Taylor MD7,8, Heiman Wertheim7,8 MD PhD, Jeremy Farrar MD, DPhil 3,8, Dinh Duy Khang6, PhD, Peter Horby7,8 * MD.

Affiliation(s): 1 National Hospital of Pediatrics, Vietnam; 2. National Institute for Infectious and Tropical Diseases, Vietnam; 3. Hospital for Tropical Diseases, Vietnam; 4. Bach Mai Hospital, Vietnam; 5. National Institute of Hygiene and Epidemiology, Vietnam; 6. Biotechnology Institute, Vietnam; 7. Oxford University Clinical Research Unit,Vietnam; 8. Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University.

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

Methods
We sought to obtained retrospective clinical data through medical record review of all laboratory confirmed cases of influenza A(H5N1) infection diagnosed in Vietnam between January 2004 and December 2006. Standard data was abstracted on clinical and laboratory features, treatment and outcome.

Results
Data were obtained on 67 cases, representing 72% (67/93) of all cases diagnosed in Vietnam over the study period. Patients presented to hospital after a median duration of illness of 6 days with fever (75%), cough (89%) and dyspnoea (81%). Diarrhoea and mucosal bleeding at presentation were more common in fatal than non-fatal cases. Common findings were bilateral pulmonary infiltrates on chest radiograph (72%), lymphopenia (73%) and raised serum transaminases (AST, 69%; ALT, 61%). Twenty-six patients died (case fatality 39%; 95% CI, 27%-51%) and the risk of death was higher in persons aged ≤16 years compared to older cases (p<0.001) and in patients who did not receive oseltamivir treatment (p=0.048). The most reliable predictor of a fatal outcome was the presence of both neutropenia and raised ALT at admission, which correctly predicted 91% of deaths and 82% of survivals.

Conclusion
Our data suggest that respiratory symptoms with pulmonary infiltrates on chest x-ray plus lymphopenia are the best diagnostic constellation, whilst neutropenia and raised serum transaminases may be the best prognostic indicators. Oseltamivir treatment shows benefit but treatment with corticosteroids is associated with an increased risk of death.