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Influenza (Flu) Explained Clearly – Diagnosis, Vaccine, Treatment, Pathology

In 1918, a new and unusually deadly
influenza virus swept the globe, in a pandemic that we are still studying today. Dr. Taubenberger: "The 1918 pandemic caused the global deaths of probably fifty, and
maybe up to one hundred million people, making it the worst natural disaster in
all of recorded human history." But what made the pandemics so lethal? NIAID's
Dr. Jeffery Taubenberger has been studying the 1918 flu for decades. Dr. Taubenberger: "Most
people who had influenza in 1918 had a completely typical course of influenza,
like you would see today, but in 1918, a really unusually high number of people
ended up having very severe illness, meaning that they actually developed a
pneumonia, an infection of their lungs, that started out as a viral pneumonia
and then rapidly progressed in most cases to a secondary bacterial pneumonia.
They had no way to treat the viral infection, they had no way to treat the
secondary bacterial infections, so these people were just really left, in a sense,
to suffer. And this process from initial onset of infection to death by bacterial
pneumonias usually took around 10 or 11 days." Ordinarily, influenza is most deadly
in the very young and the very old. But as Dr. David Morens explains, the 1918 virus was unusual. Dr. Morens: "The two things that were different in 1918 is that the deaths in all those age groups were more than they had been in other
pandemics that we had seen, and that there was a very high rate of death in
people between the ages of 20 and 40 which had never been seen before, and
which has never been seen since." To find out why the virus was so lethal, Dr.
Taubenberger and other scientists retrieved samples of lung tissue,
preserved in paraffin, from soldiers that had died of the flu. Eventually, with the
help of tissue recovered from frozen bodies in Alaska, Dr. Taubenberger's
team was able to reconstruct the 1918 flu virus. Dr. Taubenberger: "Unfortunately, when you look at
the genome of the virus, and just compare it on paper to other influenza viruses,
nothing obvious really pops out at you as to why it would
behave this way, and yet we know that this virus is a really virulent
pathogenic virus. One of the things the 1918 virus did, and does in
experimental animal models, and there's data to say that that's what happened in
people, is that it induced a really strong and very unusual kind of
inflammatory response so that the body's response, immune response, to the virus
itself contributed heavily to lung damage and pathology, and probably
contributed to serious illness and death. So it's this very unusual inflammatory
response that's one of the key active research focuses of my laboratory, to
understand why the 1918 virus induced that, and what perhaps we could do in the
future to try to develop drugs that might target or limit aspects of the
inflammatory response as a way of treating severe viral infections."