In agar.io, the viruses are those green ‘spikey’ blobs that can cause blobs larger than them to explode into many smaller parts if they touch them. At around 150 mass points, you will split if you touch a virus in agar.io.
How can we use the viruses in our advantage?
Keep in mind that the blobs that are smaller than size 130 can hide inside of viruses without exploding.
You can use this defensively if being chased by a larger blob.
If you press w (ejecting mass) into a virus, you can feed the virus. When a virus is fed 7 times, you will create a new virus in the direction you were feeding it.
You can use this offensively to split a larger blob into many smaller parts.
If someone is trying to feed a virus into you, you can react by feeding the virus back in their direction. Not only will this prevent your own blob from getting hit by a virus, it will cause your opponent to split up into many pieces, which you can then absorb.