The immune status of a population at the termination of a severe epidemic of poliomyelitis

• Published in: The Journal of hygiene 1957-06, Vol.55 (2), p.239-253
• Main Authors: Evans, C. A., Chambers, Velma C., Giedt, W. R., Wilson, A. N.
• Format: Article
• Language: English
• Subjects: Age groups; Antibodies; Children; Epidemics; Epidemiology; Humans; Infections; Old Medline; Poliomyelitis; Poliomyelitis - immunology; School age children; Specimens; Viruses
• ISSN: 0022-1724; 2396-8184
• DOI: 10.1017/S002217240003713X

In October, November and early December 1952, an epidemic of poliomyelitis, with an attack rate exceeding 1 %, occurred in Ketchikan, Alaska, a community of approximately 6000 persons. Approximately half of the cases were paralytic. Type 1 virus was regarded as the principal cause of the epidemic because Type 1 virus was isolated from one patient, and sera from eleven of twelve paralytic patients tested were positive for neutralizing antibodies to Type 1 virus. Three patients had antibodies to Type 2 virus and eight to Type 3. Serological tests were made to determine the immune status of the general population at the time the epidemic terminated. Approximately one-third of twenty-five children from 6 months to 4 years of age had antibodies to Type 1 virus. Of the 105 children aged 5 to 9 years, approximately three-quarters were positive for antibodies to this virus. All but two of the twenty-six persons more than 9 years of age who were tested were similarly positive. Spread of Type 2 and Type 3 viruses was more limited in Ketchikan than spread of Type 1 virus. Serological evidence is presented to show that Type 3 poliomyelitis virus was present in Ketchikan some time within the 3-year-period prior to the collection of serum in December 1952. Since the proportion of children showing antibodies to Type 3 virus did not increase with age from 3 to 9 years, it is surmised that virus of this type was not prevalent for a number of years prior to its last occurrence. It is further concluded that spread of Type 3 virus must have terminated when 40 % or less of the children of pre-school age and early school age had been infected and developed antibodies. Type 2 virus apparently had not been prevalent for several years prior to December 1952. Only one of twenty-one specimens of serum from children under age 5 showed definite evidence of neutralizing antibodies and this child had resided elsewhere during the first 3 months of its life. The proportion of positive results in all ages to 9 years inclusive was well below that obtained in tests with Type 1 virus. From a review of published data concerning the age distribution of cases in the 1916 epidemic in New York, it is concluded that termination of the spread of Type 1 virus in Ketchikan occurred when the proportion of susceptibles in the general population was comparable to that in New York in each of several non-epidemic years preceding 1916. It is further evident that spread of Type 2 virus in Baltimore during a