Influenza as a cause of severe acute respiratory infection through sentinel surveillance at national and provincial hospitals in Vietnam

Introduction

Since 2011 a National Influenza Surveillance System in Vietnam has conducted SARI surveillance to collect information and inform control and prevention strategies.

Objectives

To determine the burden of influenza related SARI by gender and age.

Methods

Selected patients met the WHO's SARI definition (an acute respiratory infection with history of fever or measured temperature ≥38C°; cough onset within the last 10 days; and requires hospitalization), were enrolled at four hospitals. Demographic, clinical data and one respiratory swab specimen were collected. Specimens were tested by PCR for influenza virus.

Results

From March 2011 to April 2013, a total of 2,876 SARI patients were enrolled. The median age was 16 years (IQR 1-34 years). Of all enrolled patients, 1392 (48.4%) were children <15 years old and 1482 (51.5%) were male. 297 (10.3%) of 2,876 SARI cases were positive for influenza virus by RT-PCR. Positive rates by age group in years were 0 to <5 (26.9%), 5 to < 15 (1.7%), 15 to <25 (19.5%), 25 to <35 (25.3%), 35 to <45 (7.7%), 45 to <55 (6.7%), 55 to <65 (3.4%) and ≥65 (8.8%). Of the 297 influenza positive samples, 145(48.8%) were B, 85 (28.6%) were A/H3N2, and 67 (22.6%) were A/H1N1pdm09. Among the influenza positive patients, 45 (15.1%) were hospitalized in the ICU. At least one underlying health condition was reported by 57 (19.2%) influenza positive patients included smoking, lung disease, diabetes, liver disease, heart disease, hypertension, neurologic disease and pregnancy.

Conclusion

Influenza virus infection was identified as a cause of SARI in hospitalized patients in Vietnam. As a vaccine preventable disease, it remains a burden to the healthcare system as well as a burden to the patient and family. The 0 to <5 and 25 to <35 age groups were more affected with influenza, accounting for 52.2% of influenza positive cases. Additional studies may help to better define risk factors related to infection and disease severity, evaluate the use of influenza vaccine in reducing disease burden in Vietnam.

Disclosure of interest

None declared.