“That which can be asserted without evidence can be dismissed without evidence.” —Terry Allen
The onus is on those making the claims that viruses exist to prove they exist.
Atheists will attempt to take this quote and try to turn it around on Christians, saying the onus is on us to prove the existence of God. That is perfectly fine, as long as they can define up front what would constitute as evidence. However, there is a major problem with the atheist attempting this false “turning of the tables” (apart from the inability to actually read and understand what this quote says and means): the existence of God is not asserted without evidence.
Quite frankly, most atheists are clowns who will refuse to accept any type of evidence. They claim they want evidence, fail to define what would constitute as evidence, and then no matter what kind of evidence you produce, they reject it. They should learn to be honest with themselves and just say that no matter what sort of evidence we provide, they will never accept it.
Nevertheless, they must define up front what will constitute as evidence, and then when evidence is presented that fulfills that criterion, they have no course but to accept it. That is, if they possess the least character, integrity, and honesty.
Realistically, the onus is actually on the atheist to prove God does not exist considering the abundance of evidence they must willfully reject in order to arrive at their belief, such as the entire creation itself. Trying to convince the see-no-evidence-hear-no-evidence atheist is an exercise in futility. You might as well be beating a dead horse and expecting it to magically get up and win a race for you. Do not cast your pearls before swine. Washed pigs return to wallowing in the mud and dogs return to their vomit.