Fever as nature's engine?

Data suggest that the use of paracetamol to reduce the body temperature and alleviate the symptoms of flu is counterproductive.1 2
Infectious organisms are adapted to the temperature of the part of the body they colonise. Rhinoviruses, which infect the cooler upper airway and sinuses, grow best at 33-35ºC, so inhaling air at about 45ºC for 20 minutes significantly improves the symptoms of a common cold.3 Conversely, treating the common cold with aspirin causes a significant increase in the rate of production of the virus.4 Moreover, if fever is suppressed in ferrets infected with flu virus, illness is prolonged.5
The effect of lowering or raising body temperatures in humans with flu has not been studied, but there are good reasons to treat flu by encouraging the temperature to rise to 40ºC for at least 24 hours. The lack of such research may be due to a deep seated fever phobia stemming from pre-scientific medicine, when fever was perceived as an illness in itself. However, in the 17th century Thomas Sydenham said, "Fever is nature’s engine which she brings into the field to remove her enemy," the potential of which remains unrecognised by the public and the medical profession.

Cite this as: BMJ 2009;339:b3874
Alan W Fowler, retired orthopaedic surgeon1
1 Bridgend, Mid Glamorgan CF31 1QJ
alan@awfowler.fsnet.co.uk

References

1. McCracken J. HPA advice on antipyretics. BMJ 2009;339:b3501. (1 September.)[Free Full Text]

2. Nabulsi M. Is combining or alternating antipyretic therapy more beneficial than monotherapy for febrile children? BMJ 2009;339:b3540. (1 October.)[Free Full Text]

3. Tyrell D, Barrow I, Arthur J. Local hyperthermia benefits natural and experimental common colds. BMJ 1989;298:1280-3.[Abstract/Free Full Text]

4. Stanley ED, Jackson GG, Panusarn C, Rubenis M, Dirda V. Increased virus shedding with aspirin treatment of rhinovirus infection. JAMA 1975;231:1248-51.[Abstract/Free Full Text]

5. Husseini RH, Sweet C, Collie MH, Smith H. Elevation of nasal virus levels by suppression of fever in ferrets infected with influenza viruses of differing virulence. J Infect Dis 1982;145:520-4.[Web of Science][Medline]