How do germs spread (and why do they make us sick)? - Yannay Khaikin and Nicole Mideo

Kako se mikrobi šire (i zašto se zbog njih razboljevamo)? - Janej Kaikin i Nikol Mideo

Prevodilac: Katarina Jakovljević Lektor: Mile Živković

The sun is shining.

Sunce sija.

The birds are singing.

Ptičice pevaju.

It looks like the start of another lovely day.

Izgleda da će ovo biti još jedan divan dan.

You're walking happily in the park, when, "Ah-choo!"

Veselo šetaš kroz park, kad iznenada, "Apćiha!"

A passing stranger has expelled mucus and saliva from their mouth and nose.

Prolaznik je kinuo, izbacujući pljuvačku i šlajm iz usta i nosa.

You can feel the droplets of moisture land on your skin,

Možeš da osetiš kapljice vlage kako padaju po tvojoj koži,

but what you can't feel are the thousands, or even millions,

ali ono što ne možeš da osetiš su hiljade, ili čak milioni,

of microscopic germs that have covertly traveled through the air

mikroba, koji tajno putuju kroz vazduh

and onto your clothing, hands and face.

sve do tvoje odeće, ruku i lica.

As gross as this scenario sounds,

Ma koliko ovo zvučalo odvratno,

it's actually very common for our bodies to be exposed to disease-causing germs,

zapravo je našem organizmu sasvim normalno da bude izložen mikrobima

and most of the time, it's not nearly as obvious.

koje uzrokuju bolesti, i to uglavnom nije ovako očigledno.

Germs are found on almost every surface we come into contact with.

Mikrobi se nalaze na gotovo svakoj površini sa kojom dolazimo u kontakt.

When we talk about germs,

Kada govorimo o mikrobima,

we're actually referring to many different kinds of microscopic organisms,

mi ustvari mislimo na veliki broj različitih mikroskopskih organizama,

including bacteria, fungi,

uključujući bakterije, gljivice, protozoe i viruse.

protozoa and viruses.

But what our germs all have in common is the ability to interact with our bodies

Ali ono što je svim mikrobima zajedničko je sposobnost interakcije sa našim telima

and change how we feel and function.

i uticanje na to kako se osećamo i kako funkcionišemo.

Scientists who study infectious diseases have wondered for decades

Naučnici koji proučavaju infekcije decenijama su se pitali

why it is that some of these germs are relatively harmless,

zašto su neki mikrobi relativno bezopasni,

dok druge imaju strašan uticaj na nas i ponekad mogu biti fatalni.

while others cause devastating effects and can sometimes be fatal.

We still haven't solved the entire puzzle,

Još uvek nismo rešili celu zagonetku

but what we do know is that the harmfulness, or virulence,

ali ono što znamo je to da je štetnost ili zaraznost,

of a germ is a result of evolution.

mikroba posledica evolucije.

How can it be that the same evolutionary process

Ali kako to da isti proces evolucije

can produce germs that cause very different levels of harm?

stvara mikrobe sa veoma različitim nivoom štetnosti?

The answer starts to become clear

Odgovor će nam biti jasan ako razmislimo o načinima na koje se mikrobi šire,

if we think about a germ's mode of transmission,

which is the strategy it uses to get from one host to the next.

koju strategiju koriste da stignu sa jednog domaćina do drugog.

A common mode of transmission occurs through the air,

Najčešći način prenosa je vazduhom,

like the sneeze you just witnessed,

kijanjem, kojem ste prisustvovali,

and one germ that uses this method is the rhinovirus,

jedan od mikroba koje koriste ovaj metod je rinovirus, koji se

which replicates in our upper airways,

duplira u gornjim disajnim putevima,

and is responsible for up to half of all common colds.

i odgovoran je za više od polovine prehlada.

Now, imagine that after the sneeze,

Sada, zamislimo da posle kijanja,

one of three hypothetical varieties of rhinovirus,

jedna od tri hipotetičke varijante rinovirusa,

let's call them "too much," "too little," and "just right,"

nazovimo ih "previše", "premalo" i "baš kako treba",

has been lucky enough to land on you.

ima dovoljno sreće da dospe do tebe.

These viruses are hardwired to replicate,

Ovi virusi su programirani da se umnožavaju,

but because of genetic differences, they will do so at different rates.

ali zbog genetskih razlika to će činiti različitom brzinom.

"Too much" multiplies very often,

"Previše" će se umnožavati veoma često, što će ga učiniti uspešnim na kratko.

making it very successful in the short run.

However, this success comes at a cost to you, the host.

Međutim, ti kao domaćin, plaćaš cenu za taj uspeh.

A quickly replicating virus can cause more damage to your body,

Virus koji se brzo deli će napraviti veću štetu u tvom telu,

making cold symptoms more severe.

čineći simptome prehlade intenzivnijim.

If you're too sick to leave your home,

Ukoliko si previše bolestan da izađeš iz kuće,

you don't give the virus any opportunities to jump to a new host.

virus nema priliku da pređe na drugog domaćina.

And if the disease should kill you,

A ukoliko bi te virus ubio,

the virus' own life cycle will end along with yours.

i njegov životni ciklus bi se završio zajedno sa tvojim.

"Too little," on the other hand, multiplies rarely

"Premalo" se, sa druge strane, retko umnožava,

and causes you little harm in the process.

i nanosi malo štete u tom procesu.

Although this leaves you healthy enough to interact with other potential hosts,

Iako ćeš biti dovoljno zdrav da se družiš sa drugim potencijalnim domaćinima,

the lack of symptoms means you may not sneeze at all,

i zbog nedostatka simptoma, možda nećeš uopšte kijati,

or if you do, there may be too few viruses in your mucus to infect anyone else.

a čak i da kineš, verovatno neće biti dovoljno virusa da bilo koga zaraziš.

Meanwhile, "just right" has been replicating quickly enough

Međutim, "baš kako treba" se umnožava dovoljno brzo

to ensure that you're carrying sufficient amounts of the virus to spread

da osigura da ćeš nositi dovoljno virusa kako bi mogao da se širi

but not so often that you're too sick to get out of bed.

ali ne toliko brzo da ne možeš da ustaneš iz kreveta zbog bolesti.

And in the end, it's the one that will be most successful

I na kraju, on će biti najefikasniji

at transmitting itself to new hosts and giving rise to the next generation.

u prenošenju na novog domaćina i stvaranju nove generacije virusa.

This describes what scientists call trade-off hypothesis.

Ovo opisuje ono što naučnici nazivaju hipoteza razmene.

First developed in the early 1980s,

Prvi put razvijena 1980.

it predicts that germs will evolve to maximize their overall success

ona predviđa da će mikrobi evoluirati kako bi maksimizovali svoj uspeh

by achieving a balance between replicating within a host,

ostvarujući ravnotežu između umnožavanja unutar domaćina,

which causes virulence, and transmission to a new host.

što izaziva zaraznost, i prenošenja na novog domaćina.

In the case of the rhinovirus,

U slučaju rinovirusa,

the hypothesis predicts that its evolution will favor less virulent forms

hipoteza predviđa da će evoluirati u manje zarazne forme

because it relies on close contact to get to its next victim.

zato što se oslanja na bliski kontakt kako bi došao do sledeće žrtve.

For the rhinovirus, a mobile host is a good host,

Za rinovirus, pokretan domaćin je dobar domaćin,

and indeed, that is what we see.

I zaista, to je ono što viđamo.

While most people experience a runny nose, coughing and sneezing,

Iako većini ljudi curi nos, kašlju i kijaju,

the common cold is generally mild and only lasts about a week.

obična prehlada je obično blaga i traje svega nedelju dana.

It would be great if the story ended there,

Bilo bi super kad bi se priča ovde završila,

but germs use many other modes of transmission.

ali mikrobi koriste mnoge druge načine prenosa.

For example, the malaria parasite, plasmodium, is transmitted by mosquitoes.

Na primer, parazit malarije, plazmodijum, prenosi komarac.

Unlike the rhinovirus, it doesn't need us to be up and about,

Za razliku od rinovirusa, njemu nije potrebno da budemo pokretni,

and may even benefit from harming us

već ima koristi od toga da nam naškodi,

since a sick and immobile person is easier for mosquitoes to bite.

pošto je komarcu lakše da ujede bolesnu i nepokretnu osobu.

Za očekivati je da mikrobi koji ne zavise od kretanja domaćina

We would expect germs that depend less on host mobility,

like those transmitted by insects, water or food,

kao što su oni koje prenose insekti, voda ili hrana,

to cause more severe symptoms.

izazivaju ozbiljnije simptome.

So, what can we do to reduce the harmfulness of infectious diseases?

Pa šta možemo mi da uradimo da smanjimo štetnost i zaraznost bolesti?

Evolutionary biologist Dr. Paul Ewald

Evolucioni biolog dr Pol Evald je predložio da usmerimo

has suggested that we can actually direct their evolution

njihovu evoluciju kroz jednostavne metode kontrole zaraze.

through simple disease-control methods.

By mosquito-proofing houses, establishing clean water systems,

Postavljanjem zaštite od komaraca, obezbeđivanjem čistog vodovoda,

or staying home when we get a cold,

ili ostajanjem kod kuće kad smo bolesni,

we can obstruct the transmission strategies of harmful germs

možemo da onemogućimo strategije prenosa štetnih mikroba

while creating a greater dependence on host mobility.

stvarajući veću zavisnost od pokretljivosti domaćina.

So, while traditional methods of trying to eradicate germs

I dok tradicionalne metode borbe protiv mikroba

may only breed stronger ones in the long run,

mogu, na duže staze, samo da proizvedu snažnije vrste,

this innovative approach of encouraging them to evolve milder forms

ovaj novi pristup koji ih podstiče da razvijaju blaže forme

could be a win-win situation.

mogao bi da bude rešenje.

(Cough)

(Kašalj)

Well, for the most part.

Pa za većinu slučajeva.