Migration and Persistence of Human Influenza A Viruses, Vietnam, 2001–2008

Abstract

Understanding global influenza migration and persistence is crucial for vaccine strain selection. Using 240 new human influenza A virus whole genomes collected in Vietnam during 2001–2008, we looked for persistence patterns and migratory connections between Vietnam and other countries. We found that viruses in Vietnam migrate to and from China, Hong Kong, Taiwan, Cambodia, Japan, South Korea, and the United States. We attempted to reduce geographic bias by generating phylogenies subsampled at the year and country levels. However, migration events in these phylogenies were still driven by the presence or absence of sequence data, indicating that an epidemiologic study design that controls for prevalence is required for robust migration analysis. With whole-genome data, most migration events are not detectable from the phylogeny of the hemagglutinin segment alone, although general migratory relationships between Vietnam and other countries are visible in the hemagglutinin phylogeny. It is possible that virus lineages in Vietnam persisted for >1 year.

Nonannual seasonality of influenza‐like illness in a tropical urban setting

“…Little is known about the epidemiology of influenza virus in the tropics despite a renewed research interest in tropical influenza over the past decade resulting from increased availability of influenza surveillance and sequence data . To date, research on tropical influenza has concentrated on whether influenza epidemics exhibit annual seasonality and whether influenza viruses show patterns of year‐round persistence . A third question that has received less attention is whether syndromic influenza‐like illness (ILI) surveillance has the same peaks and troughs as molecular surveillance for influenza virus in these regions.…”

“…[16][17][18][19][20] To date, research on tropical influenza has concentrated on whether influenza epidemics exhibit annual seasonality [21][22][23][24][25][26][27][28][29] and whether influenza viruses show patterns of year-round persistence. [30][31][32][33][34] A third question that has received less attention is whether syndromic influenza-like illness (ILI) surveillance has the same peaks and troughs as molecular surveillance for influenza virus in these regions. In temperate countries, public health agencies are able to rely on ILI reporting to signal the onset of the influenza season, 1,35,36 but it is not known whether ILI and influenza correlate in tropical countries.…”

Molecular Evidence of Transmission of Influenza A/H1N1 2009 on a University Campus

“…Molecular data have been instrumental in studying the origin as well as persistence and migration of influenza viruses [1,2]. In addition, molecular studies provide detailed virus characteristics, such as type, subtype, lineage, virulence and drug resistance markers.…”

Non-annual seasonality of influenza-like illness in a tropical urban setting

“…Little is known about the epidemiology of influenza virus in the sub-tropics and tropics despite a renewed research interest in tropical influenza over the past decade resulting from increased availability of influenza surveillance and sequence data [1][2][3][4][5] . To date, research on tropical influenza has concentrated on whether influenza epidemics exhibit annual seasonality [6][7][8][9][10][11][12][13][14] and whether influenza viruses show patterns of year-round persistence [15][16][17][18][19] . A third question that has received less attention is whether syndromic influenza-like illness (ILI) surveillance has the same peaks and troughs as molecular surveillance for influenza virus in these regions.…”