It is becoming better understood what it takes to turn
ordinary bird flu virus into a mass murderer, according to medical sleuths
looking into one of the deadliest killers in history, the 1918
This issue carries more than scientific significance, as new strains and
versions flu viruses are appearing all the time. The deadliest, H5N1, has caused
millions of birds to be culled, and killing nearly 400 people in more than 12
countries worldwide since 2003.
"The big question is, 'What does H5N1 need to spread globally?' We don't
know anything about that," says Terrence Tumpey of the Centers for Disease
Control and Prevention, who pioneered the research and took part in two new
studies. "We don't even know what seasonal flu needs to spread."
According to James Paulson, a molecular biologist, answering such questions
will help us recognise the next virus capable of causing a global pandemic.
"There's a new worldwide effort to survey (influenza) viruses in birds," Paulson
says, "but the tools we have are limited. We don't know enough to assess what it
takes to make a pandemic virus. What made the 1918 virus so special was that it
could enter the human population and, within a few years, kill 50 million
1918 flu resurrected - victim's genes used
Two years ago, Tumpey led a team of researchers who resurrected the 1918
virus using genes found in a victim.
By studying the virus's 10 genes, one by one, researchers are uncovering
clues to the traits that turned the virus into a monster capable of killing so
many millions worldwide, says Tumpey.
In one study, led by Ram Sasisekharan of the Massachusetts Institute of
Technology, Tumpey, together with other researchers, provide a more detailed
picture of how two mutations allowed the virus to nest in cells in the upper
respiratory tract. It was discovered that the mutations enabled the virus to fix
itself firmly to umbrella-shaped receptors in the respiratory tract. A natural
variant of the 1918 virus, called NY18, did not have the same docking power or
spread as readily in animal tests, Sasisekharan reported.
Three genes are key
Additionally, Claudia Pappas and a team of researchers, including Tumpey,
identified three genes that appear to be key to the 1918 virus's virulence. The
researchers swapped multiple genes from the reconstructed virus with genes in
seasonal strains of flu. They found three that appeared to boost flu's ability
to multiply in human airway cells and in mice.
Paulson says that armed with such information, researchers will be able to
study a virus taken from someone in, say, Indonesia, and see whether it can
"So far that hasn't happened," he says. "That we can be grateful
Source: USA TODAY