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

Translator: Nika Kotnik Reviewer: Klavdija Černilogar Dwyer

At a Maryland country fair in 2017,

Na kmetijskem sejmu v Marylandu leta 2017

the prize pigs were not looking their best.

zmagovalni prašiči niso izgledali ravno najboljše.

Farmers reported feverish hogs with inflamed eyes and running snouts.

Kmetje so poročali o prašičih z vročino, vnetimi očmi in smrkavim rilcem.

But while fair officials worried about the pigs,

A medtem ko so zaposlene na sejmu skrbeli prašiči,

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

so marylandsko ministrstvo za zdravje skrbeli oboleli obiskovalci sejma.

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

Nekateri so božali prašiče, drugi so bili le blizu njihovega hleva;

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

a kmalu je 40 udeležencev tega sejma dobilo diagnozo: prašičja gripa.

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

Večinoma bolne živali ne okužijo ljudi.

But when they do, these cross-species infections,

A ko jih, lahko te okužbe med vrstami

or viral host jumps,

ali preskok z enega gostitelja virusa na drugega

have the potential to produce deadly epidemics.

povzročijo smrtonosne epidemije.

So how can pathogens from one species infect another,

Kako lahko torej patogeni ene vrste okužijo drugo

and what makes host jumps so dangerous?

in zakaj je preskok na drugega gostitelja tako nevaren?

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

Virusi so organski paraziti, ki lahko okužijo skoraj vse oblike življenja.

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

Da preživijo in se razmnožijo, morajo skozi tri stopnje:

contact with a susceptible host, infection and replication,

kontakt z dovzetnim gostiteljem, okužba in razmnoževanje,

and transmission to other individuals.

ter prenos na druge posameznike.

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

Vzemimo za primer človeško gripo.

First, the flu virus encounters a new host

Najprej se virus sreča z novim gostiteljem

and makes its way into their respiratory tract.

in se napoti v dihalno pot.

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

To ni težko, a da bi v tem novem telesu preživel,

the virus must mount a successful infection

mora virus uspeti z okužbo,

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

preden ga imunski odziv najde in uniči.

To accomplish this task,

Da bi to dosegli,

viruses have evolved specific interactions with their host species.

so virusi razvili posebne interakcije s svojimi gostitelji.

Human flu viruses are covered in proteins

Virusi človeške gripe so pokriti z beljakovinami,

adapted to bind with matching receptors on human respiratory cells.

ki so prilagojene na vezavo z receptorji na človeških dihalnih celicah.

Once inside a cell, the virus employs additional adaptations

Ko je enkrat v celici, se virus dodatno prilagodi,

to hijack the host cell’s reproductive machinery

da prevzame reproduktivne mehanizme celice

and replicate its own genetic material.

in množi svoj genetski material.

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

Sedaj mora virus samo zatreti gostiteljev imunski sistem ali pa se mu izmakniti

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

za toliko časa, da se dovolj namnoži in okuži več celic.

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

Na tej točki se lahko gripa prenese na naslednjo žrtev

via any transmission of infected bodily fluid.

preko okužene telesne tekočine.

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

A preprosto kihanje presene virus tudi v stik z domačimi živalmi,

plants, or even your lunch.

rastlinami ali celo vašim kosilom.

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

Virusi se neprestano srečujejo z novimi vrstami in jih poskušajo okužiti.

More often than not, this ends in failure.

Večinoma se to konča neuspešno.

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

V večini primerov sta si gostitelja med seboj preveč genetsko različna.

For a virus adapted to infect humans,

Za virus, ki je prilagojen za okužbo ljudi,

a lettuce cell would be a foreign and inhospitable landscape.

je celica solate tuja in neprijazna.

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

A v okolju kroži neverjetno število virusov,

all with the potential to encounter new hosts.

z vsemi možnostmi, da okužijo nove gostitelje.

And because viruses rapidly reproduce by the millions,

In ker se virusi hitro množijo v milijonih,

they can quickly develop random mutations.

lahko hitro razvijejo naključne mutacije.

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

Večina mutacij nima učinka ali pa so celo škodljive;

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

a majhen delež teh mutacij lahko omogoči patogenu okužbo nove vrste.

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

Možnost dobitka na tej genetski loteriji se povečuje skozi čas

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

ali če je nova vrsta zelo blizu vrsti, ki jo virus običajno napade.

For a virus adapted to another mammal,

Virus, prilagojen drugemu sesalcu,

infecting a human might just take a few lucky mutations.

za okužbo človeka potrebuje le nekaj srečnih mutacij.

And a virus adapted to chimpanzees,

Virus, prilagojen šimpanzom,

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

ki so med našimi najbližjimi sorodniki, morda ne potrebuje nobene spremembe.

It takes more than time and genetic similarity

Potrebno je več kot samo čas in genetska sorodnost,

for a host jump to be successful.

da je preskok gostitelja uspešen.

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

Nekateri virusi zlahka okužijo gostiteljeve celice,

but are then unable to evade an immune response.

a se nato ne morejo izogniti imunskemu odzivu.

Others might have a difficult time transmitting to new hosts.

Drugi se morda težje prenesejo na novega gostitelja.

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

Na primer, morda je kužna kri,

but not their saliva.

ne pa slina gostitelja.

However, once a host jump reaches the transmission stage,

Kakorkoli, ko preskok gostitelja doseže raven prenosa,

the virus becomes much more dangerous.

postane virus veliko bolj nevaren.

Now gestating within two hosts,

Sedaj se množi v dveh gostiteljih,

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

tako da imajo patogeni dvakrat večje možnosti mutacije v uspešen virus.

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

In vsak nov gostitelj poveča možnost za hudo epidemijo.

Virologists are constantly looking for mutations

Virologi neprestano iščejo mutacije,

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

ki bi lahko naredile virus, kot je gripa, bolj dovzeten za preskok.

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

A predvideti naslednjo mogočo epidemijo je velik izziv.

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

Obstaja neverjetno veliko raznolikih virusov, ki jih šele odkrivamo.

Researchers are tirelessly studying the biology of these pathogens.

Znanstveniki neprestano preučujejo biologijo teh patogenov.

And by monitoring populations to quickly identify new outbreaks,

In z opazovanjem populacije, da bi hitro odkrili nove izbruhe,

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

lahko razvijejo cepiva in zajezitve, da bi ustavili te smrtonosne bolezni.