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

Kako se mikrobi prenašajo (in zakaj povzročajo bolezni)? - Yannay Khaikin in Nicole Mideo

Translator: Aida Zečkanović Reviewer: Nika Kotnik

The sun is shining.

Sonce sije.

The birds are singing.

Ptički žvrgolijo.

It looks like the start of another lovely day.

Kaže, da se začenja še en čudovit dan.

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

Sprehajaš se po parku, ko zaslišiš: "Ačih!"

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

Mimoidoči te je poškropil s slino in sluzjo iz nosu.

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

Čutiš, kako kapljice pristanejo na tvoji koži,

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

ne čutiš pa tisočev ali celo milijonov

of microscopic germs that have covertly traveled through the air

mikroskopskih klic, ki so na skrivaj pristale

and onto your clothing, hands and face.

na tvojih oblačilih, rokah in obrazu.

As gross as this scenario sounds,

Čeprav ta scenarij zveni odurno,

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

smo pravzaprav pogosto izpostavljeni škodljivim mikrobom,

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

česar pa se največkrat niti ne zavedamo.

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

Mikrobi se nahajajo na vseh površinah, s katerimi pridemo v stik.

When we talk about germs,

Ko govorimo o mikrobih,

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

pravzaprav mislimo na različne vrste mikroorganizmov.

including bacteria, fungi,

Vključno z bakterijami, glivami,

protozoa and viruses.

praživalmi in virusi.

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

Njihova skupna lastnost je, da lahko vplivajo na naše telo,

and change how we feel and function.

na njegovo delovanje in naše počutje.

Scientists who study infectious diseases have wondered for decades

Raziskovalci infekcijskih bolezni, se že desetletja sprašujejo,

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

zakaj so nekateri mikroorganizmi neškodljivi,

while others cause devastating effects and can sometimes be fatal.

drugi pa imajo lahko uničujoče ali celo smrtonosne posledice.

We still haven't solved the entire puzzle,

Te uganke še vedno nismo rešili.

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

Vemo pa, da je stopnja škodljivosti oziroma virulenca mikroorganizma

of a germ is a result of evolution.

posledica evolucije.

How can it be that the same evolutionary process

Kako pa lahko enak evolucijski proces

can produce germs that cause very different levels of harm?

pripelje do mikroorganizmov, ki so različno škodljivi?

The answer starts to become clear

Odgovor leži v načinu prenosa mikroorganizma.

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

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

To je strategija, ki jo le-ta uporabi za prenašanje med gostitelji.

A common mode of transmission occurs through the air,

Pogost način prenosa je po zraku,

like the sneeze you just witnessed,

na primer s kihanjem.

and one germ that uses this method is the rhinovirus,

Mikroorganizmi, ki se tako prenašajo, so na primer rinovirusi,

which replicates in our upper airways,

ki se razmnožujejo v zgornjih dihalih,

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

in povzročajo kar polovico vseh prehladov.

Now, imagine that after the sneeze,

Predstavljaj si, da po kihu

one of three hypothetical varieties of rhinovirus,

ena izmed treh hipotetičnih različic rinovirusa,

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

ki jih bomo imenovali "preveč", "premalo" in "ravno prav",

has been lucky enough to land on you.

pristane na tebi.

These viruses are hardwired to replicate,

Glavni cilj virusov je pomnoževanje,

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

ki zaradi genetskih razlik v virusih poteka različno hitro.

"Too much" multiplies very often,

"Preveč" se pomnožuje hitro,

making it very successful in the short run.

zato je kratkoročno zelo uspešen.

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

Vendar pa je ta uspeh slab za gostitelja.

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

Virus, ki se hitro podvaja, v tvojem telesu povzroči večjo škodo,

making cold symptoms more severe.

zato so simptomi prehlada hujši.

If you're too sick to leave your home,

Če si prešibek, da bi zapustil dom,

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

virus nima priložnosti, da bi prešel na novega gostitelja.

And if the disease should kill you,

Če pa je bolezen smrtna,

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

se bo virusov življenjski krog zaključil hkrati s tvojim.

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

"Premalo" pa se podvaja zelo počasi

and causes you little harm in the process.

in gostitelju ne povzroča velike škode.

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

Čeprav se dovolj dobro počutiš za druženje s potencialnimi novimi gostitelji,

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

je prehlad tako blag, da mogoče sploh ne kihaš,

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

ali pa imaš v nosni sluzi premalo virusov, da bi okužil še koga.

Meanwhile, "just right" has been replicating quickly enough

"Ravno prav" pa se podvojuje s primerno hitrostjo,

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

tako da imaš v telesu toliko virusov, kot jih potrebuje za širjenje,

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

vendar pa nisi prešibek, da bi vstal iz postelje.

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

Tak virus je najbolj uspešen

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

pri širjenju na nove gostitelje in razmnoževanju.

Prej opisan princip je ena izmed različic virulenčne hipoteze.

This describes what scientists call trade-off hypothesis.

Izvira iz zgodnjih osemdesetih let 20. stoletja

First developed in the early 1980s,

in predvideva, da bodo mikrobi dosegli največji uspeh,

it predicts that germs will evolve to maximize their overall success

by achieving a balance between replicating within a host,

če v razvoju stremijo k ravnovesju med podvajanjem v gostitelju,

which causes virulence, and transmission to a new host.

kar povečuje virulenco, in prenosom na nove gostitelje.

In the case of the rhinovirus,

V primeru rinovirusa

the hypothesis predicts that its evolution will favor less virulent forms

hipoteza predvideva, da bodo evolucijsko uspešnejše manj virulentne oblike,

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

saj je za okužbo naslednje žrtve potreben tesen stik.

Idealen prenašalec rinovirusa je torej aktiven gostitelj,

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

and indeed, that is what we see.

kar opazimo tudi v naravi.

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

Kljub temu, da ima večina ljudi nahod, kašelj in kihanje,

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

je prehlad blago obolenje in traja le kakšen teden.

It would be great if the story ended there,

Na žalost se zgodba tu še ne konča,

saj se klice prenašajo tudi drugače.

but germs use many other modes of transmission.

Parazit malarije, plazmodij, na primer prenašajo komarji.

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

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

Za razliko od rinovirusov, plazmodij ne potrebuje aktivnega prenašalca

and may even benefit from harming us

in ima lahko celo korist od naše škode,

saj komar lažje piči bolno in nepremično osebo.

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

Mikrobi, ki so manj odvisni od gostiteljevega gibanja,

We would expect germs that depend less on host mobility,

like those transmitted by insects, water or food,

na primer tisti, ki z prenašajo z insekti, vodo ali hrano,

to cause more severe symptoms.

torej povzročijo hujše simptome.

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

Kaj pa lahko storimo, da zmanjšamo škodljive posledice okužb?

Evolutionary biologist Dr. Paul Ewald

Evolucijski biolog dr. Paul Ewald

has suggested that we can actually direct their evolution

predlaga, da bi usmerjali evolucijo mikroorganizmov

through simple disease-control methods.

z enostavnimi pristopi za nadzor bolezni.

By mosquito-proofing houses, establishing clean water systems,

S hišami zavarovanimi pred komarji, z oskrbo s čisto vodo,

or staying home when we get a cold,

z ostajanjem doma, ko smo prehlajeni,

we can obstruct the transmission strategies of harmful germs

lahko oviramo prenos škodljivih mikroorganizmov

in povečamo njihovo odvisnost od gibanja gostitelja.

while creating a greater dependence on host mobility.

So, while traditional methods of trying to eradicate germs

Klasične metode, s katerimi poskušamo izkoreniniti mikroorganizme,

may only breed stronger ones in the long run,

dolgoročno povzročijo razvoj odpornosti,

this innovative approach of encouraging them to evolve milder forms

ta inovativen pristop za spodbujanje razvoja blažjih oblik mikroorganizmov,

could be a win-win situation.

pa bi lahko bil prava rešitev.

(Cough)

(Kašelj)

Vsaj v večini primerov...

Well, for the most part.