CONTROL OF INFECTIOUS DISEASES 857 



Comments on Table Showing Methods of Handling the Common 

 Infectious Diseases, London, Canada 



Experiment and experience indicate that certain changes are advisable, particu- 

 larly in the length of isolation and in the currently accepted periods assigned as 

 incubation periods. Up to date, the following changes have been made in the prac- 

 tice of the London (Can.) Health Department without evil results. 



1. First line, fourth column, measles — change 3 weeks to 11 days for "clean" 

 cases {i.e., without sore throat, nose bleed, bad ears, etc.); but in cases showing sore 

 throat, nose bleed, bad ears, etc., use 18 days. 



2. No restrictions are now placed on immunes unless associating with actual 

 patients, except in diphtheria (where immunity is not considered); and in scarlet 

 fever (children excluded from school, if patient remains at home); and" in small- 

 pox which conforms to regulations for scarlet fever. 



3. First line, seventh column, mumps — change 4 weeks to 3 weeks in uncompli- 

 cated cases. German me9,sles change 3 weeks to i week in all cases. 



4. Third column, scarlet fever — "after 5 days" is in practice interpreted as "on 

 the sixth day after," and so in all other similar instances: thus measles, "after 14 

 days" means "on the fifteenth day after." , 



5. Non-immune contacts in typhoid should be observed to a date 21 days 

 beyond last exposure instead of 14; in chickenpox for 18 days instead of 16; in 

 mumps 25 days instead of 21; in German measles 16 days instead of 14. 



6. Much time may be saved non-immune contacts by careful calculation of the 

 really necessary period of observation : thus, illustrated, for measles (incubation period 

 uniform, 10 days to prodromes; 4 days more to rash); and for mumps (incubation 

 period variable, 14 days to.2S days to prodromes; J^ to i day more to enlargement of 

 parotids, etc.). 



Illustration: Measles. If a non-immune is exposed to measles July i to 4 

 inclusive, he may develop prodromes at any time between July 11 and 14 

 (inclusive), the rash following from July 15 to -18 (inclusive). Hence he may go 

 about his business safely up to July 10; come under observation July 11 to July 

 18 inclusive, and if nothing has developed be released July 19. 



Mumps: If a non-immune is exposed to mumps July i to 4, he may develop 

 prodromes at any time from July 15 to July 29, the enlargement of the parotids ap- 

 pearing a half day to a day later. Hence he may go about his business safely up to 

 July 14; come under observation to July 30; and if nothing has developed, be dis- 

 charged July 31. Similar calculations may be made for the other diseases, always 

 providing the period of exposure is definitely known. 



Disinfection 



Two systems of disinfection have been long recognized, concurrent 

 and terminal. The former concerns the daily, hourly attention to, 

 and disinfection of, everything coming in contact with the patient, 



