A Short History of Nearly Everything-第68章

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nging　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’t　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—they　knew　who　and　where　they　were—though　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；　“like　extinct　volcanoes；”　inthe　words　of　one　doctor。　in　ten　years　the　disease　killed　some　five　million　people　and　thenquietly　went　away。　it　didn’t　get　much　lasting　attention　because　in　the　meantime　an　even　worseepidemic—indeed；　the　worst　in　history—swept　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—no　one　knows　how　or　where—it　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—somewhat　amazingly—three　hundred　men　who　volunteered；　the　doctors　chosesixty…two　for　the　tests。　none　contracted　the　flu—not　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’s　widespread　distribution；　but　it　still　doesn’texplain　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’t；　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’t　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　had　died　of　mysterious；　untreatablecauses　in　1959　in　fact　had　aids。　but　for　whatever　reasons　the　disease　remained　generallyquiescent　for　another　twenty　years。

the　miracle　is　that　other　such　diseases　haven’t　gone　rampant。　lassa　fever；　which　wasn’tfirst　detected　until　1969；　in　west　africa；　is　extremely　virulent　and　little　understood。　in　1969；　adoctor　at　a　yale　university　lab　in　new　haven；　connecticut；　who　was　studying　lassa　fevercame　down　with　it。　he　survived；　but；　more　alarmingly；　a　technician　in　a　nearby　lab；　with　nodirect　exposure；　also　contracted　the　disease　and　died。

happily　the　outbreak　stopped　there；　but　we　can’t　count　on　such　good　fortune　always。　ourlifestyles　invite　epidemics。　air　travel　makes　it　possible　to　spread　infectious　agents　across　theplanet　with　amazing　ease。　an　ebola　virus　could　begin　the　day　in；　say；　benin；　and　finish　it　innew　york　or　hamburg　or　nairobi；　or　all　three。　it　means　also　that　medical　authoritiesincreasingly　need　to　be　acquainted　with　pretty　much　every　malady　that　exists　everywhere；　butof　course　they　are　not。　in　1990；　a　nigerian　living　in　chicago　was　exposed　to　lassa　fever　on　avisit　to　his　homeland；　but　didn’t　develop　symptoms　until　he　had　returned　to　the　united　states。

he　died　in　a　chicago　hospital　without　diagnosis　and　without　anyone　taking　any　specialprecautions　in　treating　him；　unaware　that　he　had　one　of　the　most　lethal　and　infectious　diseaseson　the　planet。　miraculously；　no　one　else　was　infected。　we　may　not　be　so　lucky　next　time。

and　on　that　sobering　note；　it’s　time　to　return　to　the　world　of　the　visibly　living。

。。



21LIFE　GOES　ON

　　　生小　说＋网
it　isn’t　easy　to　bee　a　fossil。　the　fate　of　nearly　all　living　organisms—over　99。9percent　of　them—is　to　post　down　to　nothingness。　when　your　spark　is　gone；　everymolecule　you　own　will　be　nibbled　off　you　or　sluiced　away　to　be　put　to　use　in　some　othersystem。　that’s　just　the　way　it　is。　even　if　you　make　it　into　the　small　pool　of　organisms；　the　lessthan　0。1　percent；　that　don’t　get　devoured；　the　chances　of　being　fossilized　are　very　small。

in　order　to　bee　a　fossil；　several　things　must　happen。　first；　you　must　die　in　the　rightplace。　only　about　15　percent　of　rocks　can　preserve　fossils；　so　it’s　no　good　keeling　over　on　afuture　site　of　granite。　in　practical　terms　the　deceased　must　bee　buried　in　sediment；　whereit　can　leave　an　impression；　like　a　leaf　in　wet　mud；　or　depose　without　exposure　to　oxygen；permitting　the　molecules　in　its　bones　and　hard