A teenager is in critical condition at a children’s hospital in Vancouver, Canada, after contracting the bird flu virus. There is a high probability that the virus evolved inside a person and caused severe illness.
The latest published genomic sequences of the virus show that the teenager was infected with the H5N1 avian influenza virus, but with new mutations that enhance its ability to infect the human respiratory tract.
The virus that caused the teenager’s illness is related, but not identical, to the H5N1 virus. There are no signs yet that the sick teenager has infected other people. An important question that requires an answer: how did the teenager become infected? He did not work at a poultry farm, and researchers found no evidence of H5N1 infection among the pets with whom he interacted. Scientists do not rule out that they will never be able to establish the source of infection.
Sequencing data shows the teenager is infected with a mixture of viruses, each close to the H5N1 lineage of viruses that are currently infecting poultry and waterfowl in the region.
The researchers noted three key differences between the poultry viruses and the juvenile virus: two mutations were found that increase the virus’s ability to infect human cells, and another that helps the virus replicate in human cells, not just bird cells.
The teenager initially had an eye infection, which turned into a severe pulmonary infection. It is possible that the virus mutated and gained the ability to penetrate the cells of the respiratory tract after it entered the teenager’s body.
Immunologist Scott Hensley of the University of Pennsylvania in Philadelphia says: “Yes, the virus could have evolved inside humans. This is an alarming development, but it does not mean that a new pandemic is imminent. There is reason for concern, but not a reason for complete madness.”