At a Maryland country fair in 2017, the prize pigs were not looking their best.
Na sajmu u Merilendu 2017. godine, nagrađene svinje nisu izgledale najbolje.
Farmers reported feverish hogs with inflamed eyes and running snouts.
Farmeri su prijavili da su svinje imale povišenu temperaturu, upaljene oči i curenje iz nosa.
But while fair officials worried about the pigs, the Maryland department of health was concerned about a group of sick fairgoers.
Dok su organizatori sajma brinuli o svinjama, zdravstveni odsek Merilenda bio je zabrinut zbog grupe bolesnih posetilaca.
Some had pet the pigs, while others had merely been near their barns; but soon, 40 of these attendees would be diagnosed with swine flu.
Neki su mazili svinje, dok su drugi samo bili blizu njihovih štala; ali uskoro je kod 40 posetilaca dijagnostikovan svinjski grip.
More often than not, sick animals don’t infect humans.
U većini slučajeva, bolesne životinje ne zaraze ljude.
But when they do, these cross-species infections, or viral host jumps, have the potential to produce deadly epidemics.
Ali kada se to dogodi, ove međuvrsne infekcije, poznate kao skokovi virusa između domaćina, mogu izazvati smrtonosne epidemije.
So how can pathogens from one species infect another, and what makes host jumps so dangerous?
Kako patogeni jedne vrste mogu zaraziti drugu, i zašto su ti skokovi domaćina tako opasni?
Viruses are a type of organic parasite infecting nearly all forms of life.
Virusi su vrsta organskih parazita koji inficiraju skoro sve oblike života.
To survive and reproduce, they must move through three stages: contact with a susceptible host, infection and replication, and transmission to other individuals.
Da bi preživeli i razmnožavali se, moraju proći kroz tri faze: kontakt sa podložnim domaćinom, infekciju i replikaciju, te prenos na druge jedinke.
As an example, let’s look at human influenza.
Na primer, hajde da pogledamo ljudski grip.
First, the flu virus encounters a new host and makes its way into their respiratory tract.
Prvo, virus gripa susreće novog domaćina i ulazi u njegov respiratorni trakt.
This isn’t so difficult, but to survive in this new body, the virus must mount a successful infection before it’s caught and broken down by an immune response.
Ovo nije previše teško, ali da bi preživeo u novom telu, virus mora da ostvari uspešnu infekciju pre nego što ga imuni sistem uhvati i uništi.
To accomplish this task, viruses have evolved specific interactions with their host species.
Da bi to postigli, virusi su razvili specifične interakcije sa svojim vrstama domaćina.
Human flu viruses are covered in proteins adapted to bind with matching receptors on human respiratory cells.
Virusi ljudskog gripa prekriveni su proteinima prilagođenim za vezivanje sa odgovarajućim receptorima na ljudskim respiratornim ćelijama.
Once inside a cell, the virus employs additional adaptations to hijack the host cell’s reproductive machinery and replicate its own genetic material.
Jednom unutar ćelije, virus koristi dodatne adaptacije da bi preuzeo reproduktivne mehanizme ćelije domaćina i replicirao sopstveni genetski materijal.
Now the virus only needs to suppress or evade the host’s immune system long enough to replicate to sufficient levels and infect more cells.
Sada virus treba samo da suzbije ili izbegne imuni sistem domaćina dovoljno dugo da bi se replicirao na dovoljne nivoe i zarazio više ćelija.
At this point, the flu can be passed on to its next victim via any transmission of infected bodily fluid.
U tom trenutku, grip može biti prenesen sledećoj žrtvi putem bilo kog prenosa zaraženih telesnih tečnosti.
However, this simple sneeze also brings the virus in contact with pets, plants, or even your lunch.
Međutim, ovo jednostavno kijanje takođe dovodi virus u kontakt sa kućnim ljubimcima, biljkama ili čak vašim ručkom.
Viruses are constantly encountering new species and attempting to infect them.
Virusi neprestano nailaze na nove vrste i pokušavaju da ih inficiraju.
More often than not, this ends in failure.
Najčešće, ovo se završava neuspehom.
In most cases, the genetic dissimilarity between the two hosts is too great.
U većini slučajeva, genetska razlika između dva domaćina je prevelika.
For a virus adapted to infect humans, a lettuce cell would be a foreign and inhospitable landscape.
Za virus prilagođen za infekciju ljudi, ćelija salate bila bi strano i neprijateljsko okruženje.
But there are a staggering number of viruses circulating in the environment, all with the potential to encounter new hosts.
Ali postoji zapanjujući broj virusa koji kruže u okruženju, svi sa potencijalom da naiđu na nove domaćine.
And because viruses rapidly reproduce by the millions, they can quickly develop random mutations.
I zato što se virusi brzo razmnožavaju u milionima, mogu brzo razviti slučajne mutacije.
Most mutations will have no effect, or even prove detrimental; but a small proportion may enable the pathogen to better infect a new species.
Većina mutacija neće imati nikakav efekat, ili će čak biti štetne; ali mali deo može omogućiti patogenu da bolje inficira novu vrstu.
The odds of winning this destructive genetic lottery increase over time, or if the new species is closely related to the virus’ usual host.
Šanse za „dobitak“ u ovoj destruktivnoj genetskoj lutriji rastu tokom vremena, ili ako je nova vrsta blisko povezana sa uobičajenim domaćinom virusa.
For a virus adapted to another mammal, infecting a human might just take a few lucky mutations.
Za virus prilagođen za drugog sisara, infekcija čoveka mogla bi zahtevati samo nekoliko srećnih mutacija.
And a virus adapted to chimpanzees, one of our closest genetic relatives, might barely require any changes at all.
A virus prilagođen šimpanzama, jednim od naših najbližih genetskih rođaka, možda neće zahtevati gotovo nikakve promene.
It takes more than time and genetic similarity for a host jump to be successful.
Za uspešan skok domaćina potrebno je više od vremena i genetske sličnosti.
Some viruses come equipped to easily infect a new host’s cells, but are then unable to evade an immune response.
Neki virusi su opremljeni da lako inficiraju ćelije novog domaćina, ali tada ne mogu da izbegnu imuni odgovor.
Others might have a difficult time transmitting to new hosts.
Drugi mogu imati poteškoće sa prenošenjem na nove domaćine.
For example, they might make the host’s blood contagious, but not their saliva.
Na primer, mogu učiniti krv domaćina zaraznom, ali ne i njegovu pljuvačku.
However, once a host jump reaches the transmission stage, the virus becomes much more dangerous.
Međutim, kada skok domaćina dostigne fazu prenosa, virus postaje mnogo opasniji.
Now gestating within two hosts, the pathogen has twice the odds of mutating into a more successful virus.
Sada, razvijajući se unutar dva domaćina, patogen ima dvostruko veće šanse da mutira u uspešniji virus.
And each new host increases the potential for a full-blown epidemic.
I svaki novi domaćin povećava potencijal za punu epidemiju.
Virologists are constantly looking for mutations that might make viruses such as influenza more likely to jump.
Virolozi neprestano traže mutacije koje bi mogle povećati verovatnoću da virusi poput gripa izvrše skok.
However, predicting the next potential epidemic is a major challenge.
Međutim, predviđanje sledeće potencijalne epidemije je veliki izazov.
There’s a huge diversity of viruses that we’re only just beginning to uncover.
Postoji ogromna raznolikost virusa koju tek počinjemo da otkrivamo.
Researchers are tirelessly studying the biology of these pathogens.
Istraživači neumorno proučavaju biologiju ovih patogena.
And by monitoring populations to quickly identify new outbreaks, they can develop vaccines and containment protocols to stop these deadly diseases.
I prateći populacije kako bi brzo identifikovali nove epidemije, mogu razviti vakcine i protokole za zaustavljanje ovih smrtonosnih bolesti.
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