The respiratory infections group analysed the early progression of the epidemic of 2009 pandemic influenza (2009 H1N1) in Ho Chi Minh City, Vietnam from 26 May 2009 until the establishment of community transmission in the second half of July 2009
Data sources included all available health reports from the Ministry of Health and relevant health authorities as well as clinical and laboratory data from the first confirmed cases isolated at the Hospital for Tropical Diseases in Ho Chi Minh City. Extensive molecular diagnostics (RT-PCR) on serial samples, viral culture, susceptibility testing, and sequencing were performed on a subset of confirmed cases. Virological and epidemiological data were combined to reconstruct the initial outbreak. From 27 April to 24 July 2009, approximately 760,000 passengers who entered Ho Chi Minh City on international flights were screened at the airport by a body temperature scan and symptom questionnaire. Approximately 0.15% of incoming passengers were intercepted, 200 of whom tested positive for
2009 H1N1. An additional 121 out of 169 nontravelers tested positive after self-reporting or contact tracing. These 321 patients spent 79% of their PCR-positive days in isolation; 60% of PCR-positive days were spent treated and in isolation. Influenza-like illness was noted in 61% of patients and no patients experienced pneumonia or severe outcomes. Viral clearance times were similar among patient groups with differing time intervals from illness onset to treatment, with estimated median clearance times between 2.6 and 2.8 d post-treatment for illness-to-treatment intervals of 1–4 d, and 2.0 d (95% confidence interval 1.5–2.5) when treatment was started on the first day of illness.
The patients described here represent a cross-section of infected individuals that were identified by at the airport, as well as mildly symptomatic to moderately ill patients who self-reported to hospitals.
Data are observational and, although they are suggestive, it is not possible to be certain whether the containment efforts delayed community transmission in Vietnam. Viral clearance data showed a rapid therapeutic response to oseltamivir when given in the first four days of illness. (PLoS Med 7(5): e1000277.