Girl, a female always getting a nasty illness (5,5)

I believe the answer is:

lassa fever

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'a nasty illness' is the definition.
The definition suggests a singular noun which matches the answer.

'girl a female always' is the wordplay.
'girl' becomes 'lass' (lass is a kind of girl).
'female' becomes 'f' (common abbreviation).
'always' becomes 'ever' (synonyms).
'lass'+'a'+'f'+'ever'='LASSA FEVER'

'getting' is the link.

Can you help me to learn more?

(Other definitions for lassa fever that I've seen before include "Acute viral disease" , "Tropical viral disease that could kill" , "ailment" .)

I've seen this clue in The Guardian.

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