New research has discovered that the widespread use of medications that reduce fever lead to tens of thousands more cases of Influenza, and more than a thousand deaths attributable to Influenza, each year across North America. These drugs include ibuprofen, acetaminophen and acetylsalicylic acid.
Fever isn’t just the result of you being stricken by a disease, it is part of the body’s defense system to counter an infection. Influenza viruses invade the body because they also have adapted to body temperatures of around 37 degrees. Raising the temperature will create a more hostile environment for the virus. Fever can actually help lower the amount of Influenza viruses in a sick person's body and reduce the chance of transmitting disease to others, taking drugs that reduce fever can increase transmission.
Computer models can calculate the results and the bottom line is that fever suppression increases the number of annual cases of Influenza by approximately five per cent, corresponding to more than 1,000 additional deaths from Influenza in a typical year across North America.
Which means that widespread use of fever-reducing drugs is likely to lead to more illness and death than would be expected in a population that is not exposed to these drugs.
 Earn et al: Population-level effects of suppressing fever in Proceedings of the Royal Society B - 2014