1918 Spanish Flu Pandemic Was Likely Bird Flu
Recent Deaths Show No Signs of Human-to-Human Transmission of 'Bird Flu'
Feb. 5, 2004 -- The so-called "bird flu" outbreak in Vietnam and Thailand has scientists scratching their heads. But this may not be the first of its kind. Now there's talk that the 1918 Spanish Flu pandemic, which killed 20 million people worldwide, may have also been a form of bird flu -- but one that involved a genetic change in the virus.
Two studies may help explain what made the virus so lethal. The evidence shows that the virus may have originated as a bird-borne virus and changed its genetic makeup, and as a result it was passed on to humans. In making these changes the human immune system was caught off-guard.
As part of those studies, scientists analyzed viral gene samples taken from flu victims preserved in the Alaskan permafrost. This information has allowed them to reconstruct certain proteins of the 1918 influenza virus, such as the "hemagluttinin membrane glycoprotein," that were involved in this transformation process.
These proteins allow the flu virus to enter cells and are a specifically designed to infect one species type or another, writes researcher S. J. Gamblin, PhD, a molecular biologist with the Howard Hughes Medical Institute at Harvard University in Boston. His paper appears in the current online edition of Science.
Changes in these proteins may answer questions as to how the current bird flu, affecting birds in countries throughout Asia, is infecting and killing some humans.
Avian influenza A viruses do not usually infect humans; however, several instances of human infections and outbreaks have been reported.
Before a virus can infect one species and then others, the genetic makeup of the virus has to change as it replicates. Strains of viruses from different species can swap genetic material creating a new strain, one that has the potential to infect more than one species, like Gamblin discovered.
If a bird flu virus swaps genetic material with a human form of the virus, this process creates a virus that can now spread from human to human.
Humans can catch the bird flu virus from infected birds or surfaces contaminated with excretions from infected birds. Genetic analyses show that none of the bird flu viruses isolated from people have obtained any new genes that might make them more easily spread among humans.
According to the CDC, the virus does not appear to be efficiently transmitted from birds to humans, and it does not appear to be transmitted efficiently from one person to another. In fact, the CDC has not documented that it's been transmitted from one person to another, but they know from previous situations involving avian influenza strains that occasionally a person-to-person transmission may occur, and these viruses are prone to evolve over time, so there's always the possibility that transmission could be more efficient.