From New Scientist 25 January 2014 page 12
It appears that high temperatures, called fever, in the human body are a method of killing flu virus. Painkillers like paracetamol act to reduce fever. In this way, it encourages the virus. A 1982 study on ferrets showed that lowering temperature caused them to produce more flu virus.
A mathematical model suggested that the use of painkillers to reduce fever is increasing flu transmission by 5%. This would translate in up to 2,000 extra deaths each year in the USA alone.
The suggestion is that paracetamol and aspirin for flu should be used conservatively.