03-09-2015 07:00

In 2011, Knut, the celebrity polar bear, died at Berlin Zoo. He was only four years old when he fell into his enclosure pool.

Soon after his death, scientists found out that his brain was swollen. That is what caused him to lose balance and fall into the water. However, nobody knew why his brain was swollen.

But now, animal experts tested the bear’s brain for a condition known as “anti-NMDA receptor encephalitis”. And that it what Knut had.

The disease is not common. It affects around 200,000 people a year, but this is the first time we know about an animal which had it.

Difficult words: enclosure (an animal’s area at the zoo), swollen (to become bigger and painful, usually because of an infection), encephalitis (swollen brain).

You can read the original story and watch the video in the Level 3 section.