How do viruses jump from animals to humans? - Ben Longdon

Prevoditelj: Senzos Osijek Recezent: Sanda L

At a Maryland country fair in 2017,

Na Marylandskom sajmu 2017. godine

the prize pigs were not looking their best.

nagrađene svinje nisu izgledale najbolje.

Farmers reported feverish hogs with inflamed eyes and running snouts.

Farmeri su se žalili kako svinje imaju vrućicu, upaljene oči te im curi iz njuške.

But while fair officials worried about the pigs,

Dok su se službenici sajma zabrinuli za svinje,

the Maryland department of health was concerned about a group of sick fairgoers.

Ministarstvo zdravstva Marylanda se zabrinulo za grupu bolesnih posjetitelja.

Some had pet the pigs, while others had merely been near their barns;

Neki su dirali svinje, dok su drugi samo viđeni pored štala,

but soon, 40 of these attendees would be diagnosed with swine flu.

ali ubrzo je 40 ljudi bilo dijagnosticirano sa svinjskom gripom.

More often than not, sick animals don’t infect humans.

Najčešće bolesne životinje ne prenose bolest na ljude.

But when they do, these cross-species infections,

Ali kada se to desi, takav prijenos između vrsta,

or viral host jumps,

skok na novog domaćina,

have the potential to produce deadly epidemics.

može dovesti do smrtonosnih epidemija.

So how can pathogens from one species infect another,

Kako patogeni jedne vrste mogu zaraziti drugu

and what makes host jumps so dangerous?

i što skakanje na novu vrstu čini opasnim?

Viruses are a type of organic parasite infecting nearly all forms of life.

Virusi su vrsta parazita koji se nalaze u gotovo svim oblicima života.

To survive and reproduce, they must move through three stages:

Kako bi preživjeli i razmnožili se, prolaze kroz tri faze:

contact with a susceptible host, infection and replication,

kontakt s prijemčivim domaćinom, zarazu i razmnožavanje,

and transmission to other individuals.

te prijenos na druge pojedince.

As an example, let’s look at human influenza.

Uzmimo za primjer gripu u ljudi.

First, the flu virus encounters a new host

Prvo virus gripe dođe do novog domaćina

and makes its way into their respiratory tract.

i dospije u njegov dišni sustav.

This isn’t so difficult, but to survive in this new body,

To nije teško, ali kako bi preživio u novom tijelu,

the virus must mount a successful infection

virus mora uspješno zaraziti domaćina

before it’s caught and broken down by an immune response.

prije nego što je uhvaćen i razgrađen od strane imunosnog sustava.

To accomplish this task,

Kako bi to postigli,

viruses have evolved specific interactions with their host species.

virusi su razvili specifične odnose s njihovim domaćinima.

Human flu viruses are covered in proteins

Virusi gripe su prekriveni proteinima

adapted to bind with matching receptors on human respiratory cells.

koji su se prilagodili za spajanje s receptorima na ljudskim stanicama.

Once inside a cell, the virus employs additional adaptations

Jednom kad je u stanici, virus vrši daljnje promjene

to hijack the host cell’s reproductive machinery

kako bi preuzeo mehanizam za razmnožavanje stanice

and replicate its own genetic material.

i umnožio svoj genetski materijal.

Now the virus only needs to suppress or evade the host’s immune system

Virus mora utišati i izbjegavati imunosni sustav domaćina

long enough to replicate to sufficient levels and infect more cells.

dok se ne umnoži dovoljno i ne zarazi još stanica.

At this point, the flu can be passed on to its next victim

U tom trenu gripa se može prenijeti na druge osobe

via any transmission of infected bodily fluid.

bilo kojim putem kroz zaražene tjelesne tekućine.

However, this simple sneeze also brings the virus in contact with pets,

Obično kihanje također raspršuje virus i na vaše ljubimce,

plants, or even your lunch.

biljke, pa čak i na hranu.

Viruses are constantly encountering new species and attempting to infect them.

Virusi se stalno susreću s novim vrstama i pokušavaju ih zaraziti.

More often than not, this ends in failure.

U većini slučajeva ne uspiju.

In most cases, the genetic dissimilarity between the two hosts is too great.

U većini slučajeva, genetska raznolikost je prevelika između dva domaćina.

For a virus adapted to infect humans,

Za virus koji se razvio za napad na ljude,

a lettuce cell would be a foreign and inhospitable landscape.

stanica zelene salate je nepoznata i neprijateljska površina.

But there are a staggering number of viruses circulating in the environment,

No, u okolišu postoji mnogo virusa

all with the potential to encounter new hosts.

i svi imaju potencijal da se susretnu s novim domaćinom.

And because viruses rapidly reproduce by the millions,

Kako se virusi izrazito brzo razmnožavaju, govorimo o milijunima,

they can quickly develop random mutations.

brzo može doći do nasumičnih mutacija.

Most mutations will have no effect, or even prove detrimental;

Većina mutacija nema učinka ili se čak pokažu štetnima,

but a small proportion may enable the pathogen to better infect a new species.

ali, mali udio možda dovede do boljeg primanja virusa na novu vrstu.

The odds of winning this destructive genetic lottery increase over time,

Vjerojatnost za dobitak na ovoj genetskoj lutriji se povećava s vremenom,

or if the new species is closely related to the virus’ usual host.

pogotovo ako je nova vrsta genetski bliska s dosadašnjim domaćinom virusa.

For a virus adapted to another mammal,

Za virus koji napada druge sisavce,

infecting a human might just take a few lucky mutations.

potrebno mu je možda nekoliko mutacija kako bi mogao zaraziti i ljude.

And a virus adapted to chimpanzees,

A virusi koji napadaju čimpanze,

one of our closest genetic relatives, might barely require any changes at all.

najbliže rođake što se genoma tiče, jedva da trebaju ikakvu promjenu.

It takes more than time and genetic similarity

No potrebno je više od vremena i genetske sličnosti

for a host jump to be successful.

kako bi skok na novog domaćina uspio.

Some viruses come equipped to easily infect a new host’s cells,

Neki virusi imaju oruđe kojim lako napadnu stanice novog domaćina,

but are then unable to evade an immune response.

ali se ne mogu sakriti od imunosnog odgovora.

Others might have a difficult time transmitting to new hosts.

Drugi možda imaju problem kako doći do novog domaćina,

For example, they might make the host’s blood contagious,

na primjer, ako je virus zarazan u krvi,

but not their saliva.

ali ne i u slini.

However, once a host jump reaches the transmission stage,

No jednom kada virus uspije doći do novog domaćina,

the virus becomes much more dangerous.

on postaje opasan.

Now gestating within two hosts,

Sad kad se virus razvija u dva domaćina,

the pathogen has twice the odds of mutating into a more successful virus.

dvostruko su veće šanse za uspješnu mutaciju.

And each new host increases the potential for a full-blown epidemic.

I svaka nova zaražena osoba povećava šansu za nastanak epidemije.

Virologists are constantly looking for mutations

Virolozi stalno tragaju za mutacijama

that might make viruses such as influenza more likely to jump.

koje bi mogle dovesti do skoka virusa poput virusa gripe.

However, predicting the next potential epidemic is a major challenge.

Predviđanje sljedećih potencijalnih epidemija je veliki izazov.

There’s a huge diversity of viruses that we’re only just beginning to uncover.

Postoji velika raznolikost među virusima koju tek sad otkrivamo.

Researchers are tirelessly studying the biology of these pathogens.

Znanstvenici neumorno proučavaju biologiju tih patogena.

And by monitoring populations to quickly identify new outbreaks,

Prateći populaciju kako bi otkrili potencijalnu epidemiju,

they can develop vaccines and containment protocols to stop these deadly diseases.

mogu razviti cjepiva i metode sprječavanja širenja smrtonosnih zaraza.