For almost a decade, scientists chased the source of a deadly new virus through China’s tallest mountains and most isolated caverns.
Skoro jednu deceniju naučnici su tragali za izvorom novog smrtonosnog virusa kroz najviše planine u Kini i najizolovanije pećine.
They finally found it here: in the bats of Shitou Cave. The virus in question was a coronavirus that caused an epidemic of severe acute respiratory syndrome, or SARS, in 2003.
Najzad su ga našli u šišmišima u pećini Šitau. Virus o kome je reč je koronavirus koji je izazvao epidemiju teškog akutnog respiratornog sindroma, ili SARS-a, 2003. godine.
Coronaviruses are a group of viruses covered in little protein spikes that look like a crown— or "corona" in Latin. There are hundreds of known coronaviruses. Seven of them infect humans, and can cause disease. The coronavirus SARS-CoV causes SARS, MERS-CoV causes MERS, and SARS-CoV-2 causes the disease COVID-19.
Koronavirusi su grupa virusa koji su pokriveni malim proteinskim šiljcima koji izgledaju kao krune, ili "corona" na latinskom. Postoji stotine poznatih koronavirusa. Njih sedam može da zarazi čoveka i izazove bolest. Koronavirus SARS-CoV uzrokuje SARS, MERS-CoV uzrokuje MERS, a SARS-CoV-2 uzrokuje bolest COVID-19.
Of the seven human coronaviruses, four cause colds, mild, highly contagious infections of the nose and throat. Two infect the lungs, and cause much more severe illnesses. The seventh, which causes COVID-19, has features of each: it spreads easily, but can severely impact the lungs.
Od sedam ljudskih koronavirusa, četiri izazivaju prehlade, srednje i jako zarazne infekcije nosa i grla. Dva inficiraju pluća, i uzrokuju mnogo teža oboljenja. Sedmi, koji uzrokuje COVID-19, ima karakteristike svih koronavirusa: lako se širi, ali može ozbiljno da utiče na pluća.
When an infected person coughs, droplets containing the virus spray out. The virus can infect a new person when the droplets enter their nose or mouth. Coronaviruses transmit best in enclosed spaces, where people are close together. Cold weather keeps their delicate casing from drying out, enabling the virus to survive for longer between hosts, while UV exposure from sunlight may damage it. These seasonal variations matter more for established viruses. But because no one is yet immune to a new virus, it has so many potential hosts that it doesn’t need ideal conditions to spread.
Kada zaražena osoba kašlje, kapljice koje sadrže virus se šire. Virus može da inficira novu osobu kad kapljice uđu u njihov nos ili usta. Koronavirus se prenosi najbolje u zatvorenim prostorima, kada su ljudi blizu jedni drugih. Hladno vreme održava njihove delikatne omotače vlažnim, omogućavajući virusu da duže preživi između domaćina, dok izlaganje sunčevim UV zracima može da ih ošteti. Varijacije godišnjih doba su bitnije za ustanovljene viruse. Ali zbog toga što još niko nije imun na novi virus, ima toliko potencijalnih domaćina da mu ne trebaju idealni uslovi.
In the body, the protein spikes embed in the host’s cells and fuse with them— enabling the virus to hijack the host cell’s machinery to replicate its own genes.
U telu, proteisnki šiljci se ugrađuju u ćeliju domaćina i spajaju se sa njom, omogućavajući virusu da preuzme kontrolu nad mašinerijom ćelija domaćina kako bi replikovao svoje gene.
Coronaviruses store their genes on RNA. All viruses are either RNA viruses or DNA viruses. RNA viruses tend to be smaller, with fewer genes, meaning they infect many hosts and replicate quickly in those hosts. In general, RNA viruses don’t have a proofreading mechanism, whereas DNA viruses do. So when an RNA virus replicates, it’s much more likely to have mistakes called mutations.
Koronavirus skladišti svoje gene u RNK. Svi virusi su ili RNK virusi ili DNK virusi. RNK virusi su manji i imaju manje gena, što znači da inficiraju mnogo domaćina i replikuju se brže u njima. Uopšteno, RNK virusi nemaju mehanizam za proveru, dok DNK virusi imaju. Dakle kad se RNK virus umnožava, verovatnije je da sadrži greške koje se zovu mutacije.
Many of these mutations are useless or even harmful. But some make the virus better suited for certain environments— like a new host species. Epidemics often occur when a virus jumps from animals to humans. This is true of the RNA viruses that caused the Ebola, Zika, and SARS epidemics, and the COVID-19 pandemic. Once in humans, the virus still mutates— usually not enough to create a new virus, but enough to create variations, or strains, of the original one.
Mnoge od ovih mutacija su beskorisne ili čak štetne. A neke stvaraju virus koji bolje odgovara određenim okruženjima, kao na primer novoj vrsti domaćina. Epidemije često nastaju kada virus skoči sa životinje na čoveka. Ovo je istina za RNK viruse koji su izazvali ebolu, ziku, epidemiju SARS-a i pandemiju COVID-19. Jednom kad je u ljudima, virus i dalje mutira, ali ne dovoljno da stvori novi virus, ali dovoljno da stvori varijacije ili sojeve originalnog virusa.
Coronaviruses have a few key differences from most RNA viruses. They’re some of the largest, meaning they have the most genes. That creates more opportunity for harmful mutations. To counteract this risk, coronaviruses have a unique feature: an enzyme that checks for replication errors and corrects mistakes. This makes coronaviruses much more stable, with a slower mutation rate, than other RNA viruses.
Koronavirusi imaju nekoliko ključnih razlika od većine RNK virusa. Oni su jedni od najvećih, što znači da imaju najviše gena, To stvara više prilika za štetne mutacije. Kako bi se suprotstavili ovom riziku, koronavirusi imaju jedinstvenu odliku, a to je enzim koji proverava greške replikacija i ispravlja greške. Zbogo ovoga su koronavirusi mnogo stabilniji, sa sporijom stopom mutacije od drugih RNK virusa.
While this may sound formidable, the slow mutation rate is actually a promising sign when it comes to disarming them. After an infection, our immune systems can recognize germs and destroy them more quickly if they infect us again so they don’t make us sick. But mutations can make a virus less recognizable to our immune systems— and therefore more difficult to fight off. They can also make antiviral drugs and vaccines less effective, because they’re tailored very specifically to a virus. That’s why we need a new flu vaccine every year— the influenza virus mutates so quickly that new strains pop up constantly. The slower mutation rate of coronaviruses means our immune systems, drugs, and vaccines might be able to recognize them for longer after infection, and therefore protect us better.
Dok ovo može da zvuči strašno, spora stopa mutacija je zapravo povoljna šansa za njihovo razoružavanje. Nakon infekcije, naši imuni sistemi mogu da prepoznaju klice i unište ih brže ako nas inficiraju ponovo tako da se ne razbolimo. Mutacije mogu da stvore viruse koji su manje prepoznatljivi našim imunim sistemima, i zbog toga je teže izboriti se sa njima. Zbog njih su takođe antivirusni lekovi i vakcine manje učinkoviti jer su oni prilagođeni specifično za svaki virus. Zato nam treba vakcina protiv gripa svake godine, Virus gripa mutira toliko brzo da konstantno iskaču novi sojevi. Sporija stopa mutacija koronavirusa znači da naši imuni sistemi, lekovi i vakcine možda mogu da ih prepoznaju duži period nakon infekcije,
Still, we don’t know how long our bodies remain immune to different coronaviruses. There’s never been an approved treatment or vaccine for a coronavirus. We haven’t focused on treating the ones that cause colds, and though scientists began developing treatments for SARS and MERS, the epidemics ended before those treatments completed clinical trials.
stoga i da nas bolje štite. Ipak, ne znamo koliko dugo naša tela ostaju imuna na različite koronaviruse. Nikada nismo imali odobrenu terapiju ili vakcinu za koronavirus. Nismo se fokusirali na lečenje onih koji izazivaju prehlade, a iako su naučnici započeli razvijanje terapija za SARS i MERS, epidemije su prestale pre nego što su završene kliničke studije za te terapije.
As we continue to encroach on other animals’ habitats, some scientists say a new coronavirus jumping to humans is inevitable— but if we investigate these unknowns, it doesn’t have to be devastating.
Dok mi i dalje zadiremo u druga životnjska staništa, neki naučnici kažu da je skakanje novog koronavirusa na čoveka neizbežno, ali ako istražimo ove nepoznate stvari, ne moraju da budu pogubne.