On Viruses And Vaccines

One of the worst natural disasters in recorded history was caused by a virus The influenza pandemic of 1918 struck every major U. S city dropping people where they stood There were at least twenty million people killed worldwide And it's probably the worst pandemic the world has ever known There were more people killed from influenza than there were from the First World War The War itself was the problem If there had been no war that year's strain would have stayed isolated But when Allied troops met in northern France to exchange fire with the enemy they also exchanged a lethal strain of flu So it began It then went from France to the United States and it disseminated from Boston At Fort Devins Massachusetts one case of flu turned into more than six thousand cases between September 1 st and September 18th It took only seventeen days India lost nearly four percent of its population Alaska eight percent In the South Seas the death rate was twenty percent People were absolutely panicked because somebody could be playing bridge one night and they would be dead the next day And so they did all kinds of things They were wearing face masks and ah in fact the police all wore face masks They were carrying little pouches of garlic and onion just anything that they thought would protect them from the flu They had no idea that they were leaving exposed the very place where flu enters the body... their noses Nothing was known about how to cope with it And that is something that began to emerge when we got into the 1930's 1940's 1950's By that time there was enough knowledge and experience and the development of techniques to make it possible to proceed Never before in history have doctors been able to do so much to preserve your health as they can today And almost everywhere in medicine the parade of advances that will benefit countless millions has just begun Vaccines became a scientist's dream They promised to rid the world of viral disease Curiously the word vaccine comes from a cow disease called vaccinia In the 18th Century the beauty of milkmaids was a cliche They alone seemed to be spared from smallpox An English country doctor named Edward Jenner observed that a surprising number of milkmaids caught a mild measles-like illness called cowpox known officially as vaccinia Jenner extracted the virus from blisters and infected a child... his own infant son Then he inoculated the boy with live smallpox virus It was shockingly risky But it worked The initial cowpox injection did cause mild sickness but it was enough like smallpox that his body eventually built an immunity to both diseases We have evolved our own defense mechanisms over the years We know this is the immune system which is a very complex system containing many different kinds of cells and functions whose major purpose is to recognize what's foreign and attempt to rub it out The immune system has three major functions which are working in your body right now at this very second Antibodies are proteins that bind to the surface of the virus flagging it for death The body's white cells move in to destroy virus-infected cells Once you have been infected with a virus memory cells will immediately recognize it if it enters your body again This is why vaccines are so effective The body remembers what the fake virus looks like so it can protect you when the real virus comes along One of the most common ways to make a vaccine is to grow it in an unnatural host Chicken embryos are used to grow human viruses like yellow fever measles, mumps and influenza Influenza has been grown on in eggs for many many years It's our standard way of producing virus It can also be grown in tissue culture and grows very well in tissue culture but you can't produce enough tissue culture to make large doses required for industrial use Every year flu virus is injected into eggs After several transfers from egg to egg the virus will have become better adapted to growing in chicken cells than human cells When injected into a human it looks enough like the enemy to cause immunity but isn't strong enough to cause sickness The flu virus has found a way around the immune system by mutating changing the way it looks Sometimes it changes only slightly Other years the change is radical and we are defenseless Sometimes you can get partial immunity which will give you some protection But when we have what we call a shift that is usually what occurs when we have major epidemics Then the immune system doesn't recognize the flu at all Bears no resemblance to anything the antibodies have seen before How much a virus can change depends on how it's made If it has genetic material arranged in the familiar double-helix DNA then it's pretty stable from generation to generation In reproduction when the DNA strands unzips to become two DNA strands a kind of molecular spelling checker watches the new molecules form to make sure the two copies are identical The DNA viruses have a nice copy-editing system so they will correct their own errors which means that the frequency of mutation is low The RNA viruses do not have those And this explains why RNA viruses are so virable These viruses change all the time Which is why the vaccine for a DNA virus like smallpox works decade after decade while every year we need a new vaccine for RNA viruses like influenza This frozen library is Doctor Herlocher's collection of flu strains that have evolved over the years These viruses are not dead just dormant Each vial represents a different year a different strain If you warmed up and breathed flu vintage 1980 you'd probably get sick Some vintages of flu are spontaneous mutations Other epidemics can be traced back to ducks and pigs They end up with names like Swine flu or the Hong Kong flu or the Asian flu because they often come from countries where people live close to their farm animals Influenza has the added advantage of crossing from one species to the next Each time this happens the strain changes We have the ducks pooping in the water We have the pigs drinking the water And pigs are supposed to be the mixing vessels So you have the genes from the avian from the ducks mixing up with the pig's influenza genes and you can get a whole new strain And that means a lot of work for scientists at the World Health Organization and Centers for Disease Control in Atlanta Every year it's a race against time CDC Influenza Surveillance Laboratory Information is gathered from flu-watch centers around the world and used to predict what new strain is coming our way Once this is determined a new vaccine is developed... hopefully in time