The effect of the disease on antipyretics in the treatment of the infection: systematic review and meta-analysis. 2010, Eyers, J R Soc Med

A systematic review and meta-analysis of the use of antipyretic drugs (antipyretic drugs) during influenza on mortality. Randomized and placebo-controlled studies in humans have not been conducted, eight animal studies (mice and chickens) have been found.
Antipyretics (aspirin, paracetamol, diclofenac) increased the death rate by 34% during influenza.
Paracetamol and ibuprofen are recommended for children and adults as antipyretic during influenza, despite the lack of scientific evidence of their effectiveness and safety. There is evidence that a fever during a disease increases the chances of survival, and that the use of antipyretics may have an adverse effect on the course of the disease Antipyretics increase the risk of death in mammals with various bacterial, viral and parasitic diseases.
There are also evidences of negative influence antipyretics for bacterial pneumonia (possible complication of influenza) in animals, which can complicate the flu even more. Like the influenza virus, many strains of pneumococcus are sensitive to temperature, and die at 40-41°C. The use of aspirin in pneumococcal infection increased mice mortality by 2-3 times.