BBC Focus - 04.2020_

Q&A

Everyanimalspecieshostsuniquevirusesthat
haveadaptedtoinfectit.Overtime,someofthese
havejumpedtohumans– theseareknownas
‘zoonotic’viruses.Asourpopulationsgrow,we
moveintowilderareas,whichbringsusintomore
frequentcontactwithanimalswedon’tnormally
havecontactwith.Virusescanjumpfromanimals
tohumansinthesamewaythattheycanpass
betweenhumans,throughclosecontactwithbody
fluidslikemucus,blood,faecesorurine.
Aseveryvirushasevolvedtotargeta particular
species,it’srarefora virustobeabletojumpto
anotherspecies.Whenthisdoeshappen,it’sby
chance,andit usuallyrequiresa largeamountof
contactwiththevirus.Initially,thevirusis usually
notwell-suitedtothenewhostanddoesn’tspread
easily.Overtime,however,it canevolveinthenew
hosttoproducevariantsthatarebetteradapted.
Whenvirusesjumptoa newhost,theyoftencause
a moreseveredisease.Thisis becausevirusesand
theirinitialhostshaveevolvedtogether,andso
thespecieshashadtimetobuildupresistance.A
newhostspecies,ontheotherhand,mightnot
haveevolvedtheabilitytotacklethevirus.For
example,whenwecomeintocontactwithbats
andtheirviruses,wemaydeveloprabiesorEbola
virusdisease(EVD),whilethebatsthemselvesare
lessaffected.It’slikelythatbatsweretheoriginal
sourceofthreerecentlyemergedcoronaviruses:
SARS-CoV(2003);MERS-CoV(2012);andSARS-
CoV-2,thecauseofthe2019-20coronavirus
outbreak.Allofthesejumpedfrombatstohumans
viaanintermediateanimal;inthecaseofSARS-
CoV-2,thismayhavebeen pangolins, but more
research is needed.KA

TINAGOODWIN,VIAEMAIL

HOWDO VIRUSESJUMP

FROMANIMALS TO

HUMANS?

DEAR

DOCTOR...

DELICATEISSUESDEALT

WITHBYSCIENCE FOCUS

EXPERTS

Theamountofsugarsinfruitjuice

canbeequivalentto,oreven

higherthan,thatfoundinfizzy

drinks.That’sbadnews– too

muchsugarputsusatriskof

healthproblemsincludingobesity

andtype2 diabetes,aswellas

toothdecay.Withresearch

highlightingthesepotentialhealth

risks,andpublicawareness

increasing,thereputationand

popularityoffruitjuice have fallen

inrecentyears.

It’snotallbadnews.Purefruit

juicedoescontainvitamins,

mineralsandantioxidants,which

arenotgenerallyfoundinfizzy

drinks,andthesecanboostthe

immune system and help ward off

IDRINKFRUITJUICEBYTHEBUCKETLOAD.IS IT

REALLY AS BAD FOR ME AS FIZZY DRINKS?

infectionandinflammation.Sofruit

juicesaremarginallybetterforyou

thanfizzydrinks.Butnomatterhow

muchjuiceyouglugdown,it’ll still

onlycountasoneofyour

recommendedfive-a-day.Thisis

becausewhenfruitis juiced,sugaris

releasedfromthefruit’scellsas‘free

sugars’,andmostofthefibreis

removed– bothofwhichmeanthat

juiceisn’tasgood for you as the

wholefruit.

If youdoneeda fruitjuicehit,the

NHSrecommendsnomorethan

150mla day,anddrinkingwithmeals

toreducetoothdamage.Youcould

alsodiluteyourjuicestoreducethe

proportionofsugar– andthiswill

make them last for longer, too!SO

Theapproximatenumberofeggs

foundinthemouthofa parazen

fish.It’sthefirstdeep-seafish

speciesthat’sbeenfoundtobe a

mouth-breeder.

NASA, GETTY IMAGES ILLUSTRATION: DANIEL BRIGHT