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d by a bacterium called helicobacter pylori。 even though his findings were easily tested；the notion was so radical that more than a decade would pass before they were generallyaccepted。 america鈥檚 national institutes of health； for instance； didn鈥檛 officially endorse theidea until 1994。 鈥渉undreds； even thousands of people must have died from ulcers whowouldn鈥檛 have；鈥潯arshall told a reporter from forbes in 1999。
since then further research has shown that there is or may well be a bacterial ponent inall kinds of other disorders鈥攈eart disease； asthma； arthritis； multiple sclerosis； several typesof mental disorders； many cancers； even； it has been suggested （inscience no less）； obesity。
the day may not be far off when we desperately require an effective antibiotic and haven鈥檛got one to call on。
it may e as a slight fort to know that bacteria can themselves get sick。 they aresometimes infected by bacteriophages （or simply phages）； a type of virus。 a virus is a strangeand unlovely entity鈥斺�渁 piece of nucleic acid surrounded by bad news鈥潯n the memorablephrase of the nobel laureate peter medawar。 smaller and simpler than bacteria； viruses aren鈥檛themselves alive。 in isolation they are inert and harmless。 but introduce them into a suitablehost and they burst into busyness鈥攊nto life。 about five thousand types of virus are known；and between them they afflict us with many hundreds of diseases； ranging from the flu andmon cold to those that are most invidious to human well…being： smallpox； rabies； yellowfever； ebola； polio； and the human immunodeficiency virus； the source of aids。
viruses prosper by hijacking the genetic material of a living cell and using it to producemore virus。 they reproduce in a fanatical manner； then burst out in search of more cells toinvade。 not being living organisms themselves； they can afford to be very simple。 many；including hiv； have ten genes or fewer； whereas even the simplest bacteria require severalthousand。 they are also very tiny； much too small to be seen with a conventional microscope。
it wasn鈥檛 until 1943 and the invention of the electron microscope that science got its first lookat them。 but they can do immense damage。 smallpox in the twentieth century alone killed anestimated 300 million people。
they also have an unnerving capacity to burst upon the world in some new and startlingform and then to vanish again as quickly as they came。 in 1916； in one such case； people ineurope and america began to e down with a strange sleeping sickness； which becameknown as encephalitis lethargica。 victims would go to sleep and not wake up。 they could beroused without great difficulty to take food or go to the lavatory； and would answer questionssensibly鈥攖hey knew who and where they were鈥攖hough their manner was always apathetic。
however； the moment they were permitted to rest； they would sink at once back intodeepest slumber and remain in that state for as long as they were left。 some went on in thismanner for months before dying。 a very few survived and regained consciousness but nottheir former liveliness。 they existed in a state of profound apathy； 鈥渓ike extinct volcanoes；鈥潯nthe words of one doctor。 in ten years the disease killed some five million people and thenquietly went away。 it didn鈥檛 get much lasting attention because in the meantime an even worseepidemic鈥攊ndeed； the worst in history鈥攕wept across the world。
it is sometimes called the great swine flu epidemic and sometimes the great spanish fluepidemic； but in either case it was ferocious。 world war i killed twenty…one million people infour years； swine flu did the same in its first four months。 almost 80 percent of americancasualties in the first world war came not from enemy fire； but from flu。 in some units themortality rate was as high as 80 percent。
swine flu arose as a normal； nonlethal flu in the spring of 1918； but somehow over thefollowing months鈥攏o one knows how or where鈥攊t mutated into something more severe。 afifth of victims suffered only mild symptoms； but the rest became gravely ill and often died。
some succumbed within hours； others held on for a few days。
in the united states； the first deaths were recorded among sailors in boston in late august1918； but the epidemic quickly spread to all parts of the country。 schools closed； publicentertainments were shut down； people everywhere wore masks。 it did little good。 betweenthe autumn of 1918 and spring of the following year； 548；452 people died of the flu inamerica。 the toll in britain was 220；000； with similar numbers dead in france and germany。
no one knows the global toll； as records in the third world were often poor； but it was notless than 20 million and probably more like 50 million。 some estimates have put the globaltotal as high as 100 million。
in an attempt to devise a vaccine； medical authorities conducted tests on volunteers at amilitary prison on deer island in boston harbor。 the prisoners were promised pardons if theysurvived a battery of tests。 these tests were rigorous to say the least。 first the subjects wereinjected with infected lung tissue taken from the dead and then sprayed in the eyes； nose； andmouth with infectious aerosols。 if they still failed to succumb； they had their throats swabbedwith discharges taken from the sick and dying。 if all else failed； they were required to sitopen…mouthed while a gravely ill victim was helped to cough into their faces。
out of鈥攕omewhat amazingly鈥攖hree hundred men who volunteered； the doctors chosesixty…two for the tests。 none contracted the flu鈥攏ot one。 the only person who did grow illwas the ward doctor； who swiftly died。 the probable explanation for this is that the epidemichad passed through the prison a few weeks earlier and the volunteers； all of whom hadsurvived that visitation； had a natural immunity。
much about the 1918 flu is understood poorly or not at all。 one mystery is how it eruptedsuddenly； all over； in places separated by oceans； mountain ranges； and other earthly impediments。 a virus can survive for no more than a few hours outside a host body； so howcould it appear in madrid； bombay； and philadelphia all in the same week？
the probable answer is that it was incubated and spread by people who had only slightsymptoms or none at all。 even in normal outbreaks； about 10 percent of people have the flubut are unaware of it because they experience no ill effects。 and because they remain incirculation they tend to be the great spreaders of the disease。
that would account for the 1918 outbreak鈥檚 widespread distribution； but it still doesn鈥檛explain how it managed to lay low for several months before erupting so explosively at moreor less the same time all over。 even more mysterious is that it was primarily devastating topeople in the prime of life。 flu normally is hardest on infants and the elderly； but in the 1918outbreak deaths were overwhelmingly among people in their twenties and thirties。 olderpeople may have benefited from resistance gained from an earlier exposure to the same strain；but why the very young were similarly spared is unknown。 the greatest mystery of all is whythe 1918 flu was so ferociously deadly when most flus are not。 we still have no idea。
from time to time certain strains of virus return。 a disagreeable russian virus known ash1n1 caused severe outbreaks over wide areas in 1933； then again in the 1950s； and yet againin the 1970s。 where it went in the meantime each time is uncertain。 one suggestion is thatviruses hide out unnoticed in populations of wild animals before trying their hand at a newgeneration of humans。 no one can rule out the possibility that the great swine flu epidemicmight once again rear its head。
and if it doesn鈥檛； others well might。 new and frightening viruses crop up all the time。
ebola； lassa； and marburg fevers all have tended to flare up and die down again； but no onecan say that they aren鈥檛 quietly mutating away somewhere； or simply awaiting the rightopportunity to burst forth in a catastrophic manner。 it is now apparent that aids has beenamong us much longer than anyone originally suspected。 researchers at the manchesterroyal infirmary in england discovered that a sailor who h