Both are 1 letter off from the presumed correct word:

unatural + n == correctly spelled unnatural

unatural - u == correctly spelled natural

How the hell are you supposed to guess as if the context of viral sequencing is somehow easy to parse correctly?

Seriously? Is this the quality of discussion HN is regularly becoming? You want me to make an assumption? Is that how you operate in conversation - assumptions to fill in the gaps when something isn't clear?

You realize that their saying "natural" or "unnatural" completely changes what they're saying to the polar opposite, right?

So now clarity is pedantic?

Seriously?

If HN had subreddits there'd be one similar to /r/WatchRedditDie