Expression: 'To judge from his occasional snorts, he had a severe dose...'

[Tom]

Hi

Could you please explain the following sentence to me?

"To judge from his occasional snorts, he had a severe dose of catarrh."

Does it mean that the speaker judged from someone's snorting that that person had flu? Why dose?

Tom

[Conchita]

You got the general drift, Tom.

A catarrh is a type of cold. The word 'dose' is often used for a quantity of medicine or of something unpleasant: a dose of hayfever, flu, bronchitis, etc.