Posted on 10/10/2005 3:38:48 PM PDT by blam
Killer Findings: Scientists piece together 1918-flu virus
Christen Brownlee
The "Spanish" flu killed an estimated 20 million to 50 million people worldwide between 1918 and 1919. Hoping to prevent such a deadly outbreak from recurring, scientists have long strived to figure out what characteristics differentiate that strain from other, more-benign varieties. Because researchers have lacked live samples of the killer virus, however, they couldn't answer this pivotal question.
Two new studies now shed unprecedented light on the 1918 strain.
The first study caps a 9-year effort led by Jeffrey Taubenberger of the Armed Forces Institute of Pathology in Rockville, Md., to attain a complete genome sequence for the 1918 strain (SN: 3/22/97, p. 172: http://www.sciencenews.org/pages/sn_arc97/3_22_97/fob1.htm). Taubenberger and his colleagues collected virus particles from samples that had been preserved after autopsies of 1918-flu casualties and from a single additional victim interred in the Alaskan permafrost.
The virus had long since degraded in these samples, but it left behind tiny bits of RNA that encode the virus' eight major gene segments.
Previously, Taubenberger and his colleagues had used these RNA fragments to sequence five of the virus' gene segments. In the Oct. 6 Nature, the team reveals the final three sequences. The genes in these blocks code for the 1918 flu's polymerases, which are proteins crucial for a virus' replication in animal hosts.
Taubenberger's team found a striking resemblance between the 1918 virus and modern bird-flu strains, including the deadly H5N1 strain currently circulating in Southeast Asia (SN: 9/10/05, p. 171: http://www.sciencenews.org/articles/20050910/bob10.asp). These results add to evidence suggesting that the 1918 flu originated as an avian strain that acquired the capacity to infect people.
Taubenberger notes that figuring out how the virus adapted to human hosts could aid researchers in preventing modern bird-flu outbreaks from becoming pandemics in people. "If we could identify which [parts of the genome] are important in adaptation, we could provide a checklist for surveillance of strains just beginning to show adaptation to humans," he says.
Using the just-completed sequence, a team led by Terrence Tumpey of the Centers for Disease Control and Prevention in Atlanta has partially reconstructed the 1918 virus.
The researchers synthesized the eight major pieces of RNA according to the virus' genetic code. They then combined them with bits of RNA from related flu viruses. The latter genetic material enabled animal cells to read the viral genes.
Working under biosafety level 3, the second-highest level of protection against biohazards, Tumpey's team found that the reconstructed virus killed otherwise-healthy mice in 3 to 5 days. It was also lethal to chicken embryos developing inside eggs, supporting its likely origin as an avian-flu virus. When the scientists infected samples of human-lung cells with the virus, it replicated readily.
By mixing and matching the 1918 virus' genes with genes from contemporary-flu strains, the team found that the 1918 virus' polymerase genes and its hemagglutinin gene, which sneaks the virus into cells, seem to play pivotal roles in virulence. The group published its results in the Oct. 7 Science.
Flu researcher Yoshihiro Kawaoka of the University of Wisconsin–Madison suggests is that he and other researchers can now determine how the virus' genes made the 1918 flu so deadly. With that information, scientists could craft new vaccines and drugs to combat future outbreaks.
"By understanding why this [strain] was so pathogenic, we can prepare for the potential of future viruses that may appear," Kawaoka says.
Heartwarming. Superflu, anyone?
Personal family story about the 1918 flu. My father was 8 years old, his mother and the town doctor went from house to house treating flu victims. Many people died. Why my grandmother never caught the flu, nor my father or his father, has always been a kind of family miracle. Very strange given her constant exposure.
Gee! What a fantastic advance! Can the Black Death be far behind?
The Black Death Plague did not have any where near the death rate of the 1918 flu. More people died from the '1918 Flu' than all the wars in the 20th century combined.
You have to understand how something works before you can effectively fight it.
Even today, there is no known cure for the 1918 flu.
Agreed - and while the transmission method for the Black Death is thought to have been Yersinia pestis carried by fleas from rats to humans, we *still* do not know what the vector was for the 1918 'flu', whether it was a multitude of strains or just a few, and whether it was truly an airborne virus.
Good story.
My mother was born in 1917 and my dad in 1918 (bless their souls). I have always hoped that their possible exposure and survival indicates some type of immunity for me. Hope we don't have to find out.
IMMUNE SYSTEM STRENGTH! That's probably why.
Possibly, but here's a very odd little fact about the 1918 flu; it was most fatal for those between 20 and 40 and seemed to generally ignore the children and elderly.
Way, way, way out of character for influenza.
I just saw an interesting one-hour documentary the other night that said more than the 'fleas' was going on. They proposed that two different things were infecting people. (don't remember any of the specifics though)
Possibly. Certainly humanity as a species is now more resistant to 1918 (by process of, ahem, elimination).
There were other insect vectors, as I recall - I think mosquitos were carrying the disease around, too. Yersinia pestis is thought to have been the cause - it's still around; occasionally someone will get it, not seek treatment, and die.
Very good link! Thanks.
They were speaking of an entirely different disease than the one carried by fleas & mosquitos. They did point out that the spread in the northern climates was to fast (very cold regions) to have been transmitted by fleas or mosquitos in such sparcely populated regions.
There were also some contradictions in some of the symptoms reported from that period.
There were probably a number of nasty bugs running around in the Middle Ages at the time of the Black Plague that got lumped together. However, the actual Black Plague was the major killer and it only had a couple of vectors and one cause.
Modern sanitation and cleanliness is a huge benefit...
Actually, I think it was about a third of Europe overall at the time, and there were many islands of non-exposure. The death rate among people who actually came down sick was something very high, estimated at seventy to over ninety percent. You have to allow that the population of Europe in 1347 was much lower than in 1918, with the insulating effects of lower population density and more difficult travel.
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