EFFECT OF ENVIRONMENTAL 

 TEMPERATURE ON VIRAL INFECTION^ 



Duard L. Walker, M. D. 



University of Wisconsin 



Medical School 

 Madison 6, Wisconsin 



ABSTRACT 



In considering the effects of cold on viral infections, four questions seem to be of 

 particular importance. These are: (1) Can exposure to cold cause an acute but mild 

 and inapparent infection to become an apparent and severe disease? (2) Can it seriously 

 worsen an apparent viral infection? (3) Can it activate a latent viral infection? (4) What 

 are the mechanisms by which cold exerts an effect on viral infections? Indication 

 that the answers to the first three questions can be "yes" is available from studies of 

 infections in animals. Studies in this laboratory on Coxsackie infections in mice are 

 pertinent to the first question. In infant mice the Conn.- 5 strain of Coxsackie B-1 

 virus causes a generalized, lethal infection, but in adult mice the infection is limited 

 to a mild, inapparent pancreatitis. Exposure of adult mice to a 4° C environment, how- 

 ever, results in illness with essentially 100 per cent mortality. Pertinent to the second 

 question are studies on the myxoma- fibroma viruses. Marshall has shown that exposure 

 to cold increases the severity of disease in rabbits infected with attenuated strains of 

 myxoma virus. Relative to the third question, Shope has found that exposure to cold 

 weather appears to activate latent infections of swine influenza virus in swine. Although 

 the mechanisms by which cold exerts an effect on viral intections have not been studied 

 extensively, there is growing evidence that it may be by simply lowering tissue tempera- 

 ture to one more favorable for multiplication of the infecting virus. At normal tempera- 

 tures Conn.- 5 Coxsackie virus multiplies only in the pancreas of the adult mouse. Ex- 

 posure to 4° C results in reduction of body temperature by 1.0° C to 1.5° C and in multi- 

 plication of virus in many organs. Exposure of mice to 36° C raises their body tempera- 

 ture 2° C and inhibits multiplication in all tissues, including the pancreas. Study of 

 Conn. -5 virus multiplication in in vitro cultures reveals that the virus does not multiply 

 well in adult mouse tissues at 37° C or at higher temperatures, but does multiply well 

 at 35° C. 



1 Studies by the author on this subject were supported by grants from the National 

 Institute of Allergy and Infectious Diseases and the National Cancer Institute. 



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