Almost certainly natural.
If someone were to design a bug to kill - it wouldn’t be one that could be easily avoided by F#^@&# washing your vegetables.
Something spread by a cough would be much more dangerous.
Just use a little logic.
And wash your vegetables.
There is no confirmation, as yet, that the bug is spread by vegetables. This was the original notion, now disproved. The article notes that the origins are unknown.
It may be spreading through the water system. In which case, washing ones vegetables is bad news.
The illness is now in Great Britain, and people have been warned that it could directly transmit from one person to another.