Translation:This new disease is quite dangerous.
This was written years ago. Long before we had even heard of the coronavirus. There have always been dangerous viruses.
Duolingo has prepared a link on the Covid-19 https://forum.duolingo.com/comment/37177899
And this in GReek
Be well and take precautions.
Ok, let's start with πολύ which is pretty straightforward and means: very, much, many, a lot, etc.
It can also with the right context mean "too" as in "too much" (but 'πάρα πολύ is also correct and more common).
Also, something like " really" .e.g. Διάβασα πολύ σκληρά αυτή τη χρονιά. I studied really hard this year. Again depending on context and nuance.
Αρκετά is translated in the dictionaries as: enough, quite, pretty, rather. And here is where the confusion comes in.
"enough" in English means "as much/many as is needed" "sufficient" In Greek, it would be "επαρκής" which is rather formal.
The problem occurs when "αρκετά" is used to mean "a lot etc" (πολλές ετψ) rather than "sufficient/enough), for example, in a sentence like this:
This is correct: "Είχαμε πολλές καρέκλες για το πάρτι, αλλά μερικοί άνθρωποι έπρεπε να μένουν όρθιοι επειδή δεν είχαν καρέκλα." If we use "a lot of" or "many" we get: "We had a lot of chairs, but some people had to remain standing because they didn't have a chair."
If we use "enough" this turns into nonsense:
"We had enough chairs, but some people had to remain standing because they didn't have a chair." If you have "enough/sufficient/as much as is necessary" everyone would have had a chair.
Sorry for being so long winded. In conclusion, we need to be sure whether we mean "a lot" or "as much as is needed" when using "αρκετά".