Answer:
reassuring
Explanation:
The definition of the tone in literature is that it is a manner in which the author expresses his attitude towards the topic, the atnosphere he creates.
The particular tone can be achieved by means of choice of words, level of formality, syntax use, diction etc.
Here, we see that the author sound optimistic; he brings good news about the disease stating that the chance of catching it is astronomically low. This optimistic, comforting and encouraging type of writing gives this passage a reassuring tone.
I would not talk when not told, and help around
