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Spatial fluidity of H1N1 likely to impede on-campus control methods
Holmes E. J Virol. 2011;85:6923-6929.
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Various strains of the 2009 H1N1 influenza virus were isolated from students at the University of California, San Diego, from October to November 2009. The strains moved onto the campus independently, with little on-campus transmission, suggesting on-campus methods for controlling the spread of influenza may be insufficient to fully prevent transmission.
“Although our study considers only a single community, the large number of independent virus entries and their diverse positions on phylogenetic trees indicate that [University of California, San Diego] contains an effectively global sample of H1N1/09 genetic diversity,” according to Edward C. Holmes, PhD, of the department of biology at Pennsylvania State University, and colleagues.
In the observational study, Holmes and colleagues sampled isolates from 57 students at UCSD from October to November 2009 to examine pathways and determinants of H1N1 virus transmission and to further assess complete viral genome sequences.
Between 24 and 33 “independent introductions of H1N1/09 into the UCSD community” were identified. Overall, minor geographical clustering by ZIP code or student residence was observed, suggesting a low-level of on-campus transmission and significant spatial mixing, according to the researchers.
“This is a very connected world, which assists viral transmission,” Holmes told Infectious Disease News. “Most of the transmission appeared to occur outside of the campus itself — this means methods to control influenza transmission that are only applied on campus, as they may well be, are not going to be effective in controlling the virus. With an understanding of how often, and from what potential sources viruses enter specific communities, we may be able to target better control studies or design vaccine or antiviral treatment protocols that anticipate certain transmission pathways.” – by Ashley DeNyse
Disclosure: Dr. Holmes reports no relevant financial disclosures.
This interesting paper assessed the spatial diffusion (phylogeography) of 2009 H1N1 influenza A virus among students seeking care at the student health service at the University of California, San Diego, during a 1-month period of the second wave of the recent influenza pandemic using whole-genome sequencing and phylogenetic analysis of viruses obtained from ill students.
The investigators detected evidence of at least 24 separate virus introductions into the university community during the study period. There was no evidence of a point source outbreak or clustering by university residence; only a few clusters of limited intra-university transmission were identified. The authors conclude that transmission may have been more frequent among students in classrooms and social areas. However, the study did not include faculty or staff, so the role that they played in introduction and transmission is not clear. These results are important to consider when thinking about intervention strategies and highlight the fact that large universities are dynamic microenvironments whose students, staff and faculty interact with surrounding communities and the world at large. This study also reminds us that we have much to learn from the application of modern molecular tools to the study of influenza epidemiology.
– James Hughes, MD
Infectious Diseases News Editorial Board member
Disclosure: Dr. Hughes reports no relevant financial disclosures.
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