outbreak

A sheet of paper tears where tension exceeds strength. Epithelium, the cell sheet lining our organs, behaves similarly, but until recently models could not show how tears appear in it. The classical vertex model describes tissue as a network of polygons tightly packed together and forbids cells from detaching.

A tightly stretched membrane, squeezed into a narrow case, decides on its own where to burst. So does a cell: when it is cramped, the point of division shifts from the middle, and the two halves come out unequal. Previously, it was thought that such asymmetry is predetermined by chemical labels, but the new work shows that mechanics alone is enough.

A crowd of pedestrians in a square moves chaotically: each person goes their own way, occasionally bumping into others. If every third person in that crowd wears a protective suit that blocks the pathogen, the rhythm of disease spread changes abruptly. That is exactly the scenario scientists reproduced by simulating 3000 self-propelled particles that repel each other and become infected upon close contact.

The classroom goes quiet after the lesson, but the echo still rings in the child's head: faces, objects, places. It is this echo, not the lesson itself, that decides what will stay in memory. For the first time, researchers have caught it in children aged 6 to 17. Children memorized scenes inside an MRI scanner: they were shown a room, then an object or a face in a particular spot.

Every winter, hospitals fill up, and by summer they seem to empty. Epidemics breathe like the tide. But why do waves of disease keep rolling in, even without new mutations? Mathematicians found an answer in a tug-of-war between two strains. Within a single epidemic, two virus variants often coexist.

A mail carrier delivers letters along one-way streets. As long as he only drives forward, the route is simple and predictable. But if U-turns are suddenly allowed, he'll start doubling back, crossing his own tracks, and the delivery pattern gets tangled. That's roughly how an infection behaves when people can get sick more than once.

A jazz ensemble: at first, a cacophony of random notes. Then — a catchy riff that plays over and over. Such is the riddle of the origin of life — only in the language of chemistry.

A disease outbreak is like a wildfire: the fire runs through dry grass, and its speed depends on wind and humidity. But an infection has its own 'wind'—how often people infect each other. When this rate changes along with the fraction of already infected, the epidemic wave can behave differently.

Ordinary models assume that infection is like a steady flow of water that washes over everyone equally. In reality, the stream from a sick person fluctuates: right after infection it barely trickles, then turns into a raging downpour, and later subsides. The chance of catching the virus depends on the strength of this flow at the moment of contact.

When a pipe bursts in the basement, a plumber acts step by step: locates the leak, measures the pressure, determines the cause, patches it up, and checks if it's dry. The same recipe — the standard model DMAIC — is being proposed against epidemics. First, they determine the scope — how many hospital beds are occupied, which industries are sagging.

In the web of life, predators and prey exchange carbon and water, and each act of eating slightly increases the universe's disorder. But the intrusion of disease turns this system into a giant seesaw. When a mid-level predator gets sick, its hunting abilities decline, and it becomes easy prey.

In the quiet of cold molecular clouds, where interstellar gas under gravity condenses into dense clumps, the birth of massive stars is one of the great puzzles of astrophysics.

In the summer of 2021, comet 7P/Pons-Winnecke put on quite a show. A network of telescopes, the Las Cumbres Observatory, tracked it for nearly three months and counted eight sudden outbursts.

A living organism is a machine that constantly channels energy through itself and converts it into heat. This internal cycle is called internal entropy production (a measure of energy dissipation). But about 2.5 million years ago, our ancestors switched on a second loop — an external one. They picked up a sharpened stone, and then a burning branch.

A drop of blood from a fingertip is like a photograph. One is just a snapshot, but collect them over years and you get a movie of your health.

An epidemic is not just a virus: it's millions of personal decisions. One person keeps riding the subway; another locks themselves at home. Classical models describe the average behavior of a crowd but don't ask why each individual acts that way.

An epidemic is like a fire in a dry forest: a spark flares up, the flames leap from tree to tree, and within a week the whole area is burning. A hundred years ago, scientists devised a simple mathematical model for such a fire: they divided people into those who had not yet fallen ill, those who were ill, and those who had already recovered.

An epidemic is like a forest fire: the flames race toward where there are more dry branches. Similarly, a virus spreads faster where people live in closer quarters. But old mathematical models described infection as an ink blot spreading evenly across paper.

A density of four people per square meter is the threshold beyond which a crowd ceases to be a sum of individual pedestrians and becomes something else. In Pamplona's Plaza Consistorial during the San Fermín festival, local density reached nine people per square meter.