An early report from newly established laboratory-based influenza surveillance in Lao PDR

Abstract

Background: Prior to 2007, little information was available about the burden of influenza in Laos. We report data from the first laboratory-based influenza surveillance system established in the Lao People's Democratic Republic.

Methods: Three hospitals in the capital city of Vientiane began surveillance for influenza-like illness (ILI) in outpatients in 2007 and expanded to include hospitalized pneumonia patients in 2008. Nasal/throat swab specimens were collected and tested for influenza and other respiratory viruses by multiplex ID-Tag respiratory viral panel (RVP) assay on a Luminex 100x MAP IS instrument (Qiagen, Singapore).

Results: During January 2007 to December 2008, 287 of 526 (54.6%) outpatients with ILI were positive for at least one respiratory virus. Influenza was most commonly identified, with 63 (12.0%) influenza A and 92 (17.5%) influenza B positive patients identified. In 2008, six of 79 (7.6%) hospitalized pneumonia patients were positive for influenza A and four (5.1%) were positive for influenza B. Children <5 years represented 19% of viral infections in outpatients and 38% of pneumonia inpatients.

Conclusion: Our results provide the first documentation of influenza burden among patients with febrile respiratory illness and pneumonia requiring hospitalization in Laos. Implementing laboratory-based influenza surveillance requires substantial investments in infrastructure and training. However, continuing outbreaks of avian influenza A/H5N1 in poultry and emergence of the 2009 influenza A(H1N1) pandemic strain further underscore the importance of establishing and maintaining influenza surveillance in developing countries.

Figure 1

Proportion of outpatients meeting the ILI case definition (blue, n = 161; total outpatient consultations in the three sentinel hospitals) and percentage of laboratory‐confirmed influenza positive cases (red, n = 322; total ILI specimens tested) by month in 2008.