The incidence of poliomyelitis virus in normal children aged 0–5 years A report on a study by the Public Health Laboratory Service and Local Health Authorities

A survey has been made of a sample of children aged 0–5 years in a number of areas in England and Wales for the presence of symptomless excreters of poliomyeitis virus. The investigation covered a 2-year period from the spring of 1957 to the summer of 1959. Altogether 28, 797 specimens were examined of which 140 were positive for Type 1 virus, 24 for Type 2, and 44 for Type 3, the corresponding rates being 4·85, 0·83, and 1·53 per 1000 specimens respectively. It is estimated that for every notified case of poliomyelitis there were about 140 symptoinless excreters of Type 1 virus. No accurate estimates of this ratio were possible for the other two types, but it was certainly much higher. The incidence of positive specimens was 15 per 1000 in the first and 2·6 per 1000 in the second year of the survey, but there were considerable local variations. Type 2 virus was not isolated during the second year. Most specimens were examined for the presence of salmonellae and shigellae which both had a frequency of about 2 per 1000. The salmonellae were mainly S. typhimurium, and all the shigellae were Sh. sonnei. Some information was obtained on the prevalence of other viruses. Coxsackie B virus was the most commonly isolated and in the second year was commoner than poliomyelitis virus. Its seasonal incidence was roughly the same as that of polio myelitis virus. Adenoviruses were isolated in about 6 per 1000 specimens and were most common in the winter. ECHO viruses were about half as common as adenoviruses and the maximum incidence was in the autumn. The limitations of the sampling method used and the problems of analysis of the results are discussed.