How flu bug's evolution affects disease spread

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The Oct. 29 issue of Science reports that a new study may help researchers predict how specific molecular changes in the influenza virus will help the bug to outwit the flu vaccine and cause disease outbreaks. We don’t have this information for the viral strains infecting humans—the slew of differences in how people have been vaccinated don’t lend themselves to a controlled experiment—but scientists have now collected comparable information on ponies. The findings may help researchers devise maximally effective vaccination strategies that keep up with the evolution of the influenza virus. Equine influenza vaccines have been used, particularly in racehorses, since the 1960s. Andrew W. Park and colleagues studied both vaccinated and “control” ponies infected with various strains of equine influenza. The researchers tracked changes in the amino acids of the virus’ hemagglutinin protein (one of the primary means by which the virus evades its host’s immune system) and showed how these changes influenced the way the disease spread through the population. As the virus and vaccine strains became different, the chances that a pony would become infected, as well as infectious, increased, as did the length of the infectious period. Nevertheless, even imperfectly matched vaccines may still have a benefit, because increasing the proportion of vaccinated individuals can offset the effects of the poor match, especially if the vaccine is used in conjunction with antiviral drugs, the researchers report.

Article #13: "Quantifying the Impact of Immune Escape on Transmission Dynamics of Influenza," by A.W. Park at University of Georgia in Athens, GA; J.M. Daly; N.S. Lewis at Animal Health Trust in Suffolk, UK; J.M. Daly at University of Nottingham in Leicestershire, UK; N.S. Lewis; D.J. Smith at University of Cambridge in Cambridge, UK; N.S. Lewis; J.L.N. Wood at Cambridge Infectious Diseases Consortium in Cambridge, UK; D.J. Smith; B.T. Grenfell at National Institutes of Health in Bethesda, MD; D.J. Smith at Erasmus Medical Center in Rotterdam, Netherlands; B.T. Grenfell at Pennsylvania State University in University Park, PA; B.T. Grenfell at Princeton University in Princeton, NJ.