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


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


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


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.


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.


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.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Nguyen, T., Nguyen, Y., Nguyen, T. et al. Influenza as a cause of severe acute respiratory infection through sentinel surveillance at national and provincial hospitals in Vietnam. Antimicrob Resist Infect Control 4 (Suppl 1), P13 (2015).

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