QUARANTINE IN CONTROL OF INFECTIOUS DISEASES 61 



before such an individual may be allowed to return to his 

 work. 



In smallpox the patient is invariably removed to the 

 isolation hospital of the Department of Health. Isolation 

 is maintained until all scabs have disappeared, including 

 the deep-seated "seeds" beneath the epidermis of the 

 soles of the feet. 



In epidemic cerebrospinal meningitis isolation is main- 

 tained for fourteen days, for it has been found that menin- 

 gococci in the nasopharynx of convalescents are very rare 

 after the twelfth or fourteenth day. Whenever facilities 

 permit healthy contact carriers should be sought out and 

 isolated. 



In acute anterior poliomyelitis (infantile paralysis) the 

 minimum period of quarantine is six weeks, a period fixed 

 largely as the result of experimental work on animals. 



In yellow fever it is now well established that the pa- 

 tient's blood remains infective about three days. More- 

 over, after having been bitten by an infected mosquito it 

 requires about five days for symptoms to develop. (See 

 also page 128.) Isolation, therefore, is relatively short 

 and amounts, moreover, only to screening the patient from 

 mosquitoes. 



In typhus fever the recent bacteriologic work of Plotz 

 indicates that isolation need not be maintained for much 

 beyond the return of the fever to normal. The greatest 

 danger period would appear to be four or five days pre- 

 ceeding the crisis, for at that time the typhus bacilli 

 are most numerous in the patient's blood. Inasmuch as 

 the disease is spread by lice, care should be taken to de- 

 stroy all lice by thorough washing of the patient and dis- 

 infection of his clothing and other belongings. 



