Some vaccines use a weakened live virus as their agent to immunize the host. The Australians have managed the unique feat of (accidentally) getting two of these live-virus from vaccines to recombine into a newer deadlier form of virus: oh joy.
The original virus was killing about 5% of their chicken population. The new virus is killing about 17%. Note, either number would be considered absolutely devastating if similarly deadly disease were unleashed on the world’s human population. The most comparable modern pandemic, the 1918 Spanish Influenza, is thought to have killed about 5% of the world population.
Brett Smith, RedOrbit, 13 July 2012 (hat tip: NC)
Australian scientists looking to vaccinate chicken populations against a respiratory disease may have accidentally unleashed a disease far more deadly than the one they hoped to prevent.
According to a report published this week in Science, the genomes from two different strains of the herpesvirus infectious laryngotracheitis (ILT) virus that were used in vaccines have recombined to produce more virulent ILT viruses near Sydney and Melbourne.“These new strains were formed by recombination from the different vaccine strains and that they were actually more virulent than the vaccine strains that gave rise to them,” said lead author Joanne Devlin from The University of Melbourne, Parkville.
“This is something we’ve never before seen before in the field.”