Comparative Studies on Patterns of Family Infections with Polioviruses and ECHO Virus Type I on an American Military Base in the Philippines

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Abstract
On a military base in the Philippines, a sample of 200 American families and a few native domestics was the object of a 4-month linear study for poliovirus infections. No clinical poliomyelitis was recognized on the base. Repeated specimens were collected for virus isolation and serology. Some of these were also tested for evidence of ECHO-1 virus infections. No great differences were observed in patterns of virus isolation and serological results for each type of virus infection. Poliovirus infection rates among serological susceptibles ranged from 14.2% for the 0 to 4 year age group to 5.8% for adult parents. Age-specific infection rates ranged from 12% to 5%. The annual rate in the tropics might be 3 times these figures. In all, 36 infections occurred and all 3 types of poliovirus were represented. Thirty-six ECHO-1 virus infections were found among a smaller number of families tested. The poliovirus infections occurred in 21 families. Nineteen families from fewer tested, including 5 of those with poliovirus infections, were discovered with ECHO-1 virus infections. Age-specific infection rates were higher for ECHO-1 than for polioviruses. The differences in rates were greatest in the 0 to 9 year group, being 81% for ECHO-1 virus, 59% for polioviruses. It is concluded that ECHO-1 virus is far more infectious than any of the polioviruses. Based on serological "susceptibility", 90% of the "susceptible" children developed ECHO-1 infection and 70% poliovirus infection. Rates among "susceptible" adults were 40% and 36%, respectively. No "immunes" became infected with ECHO-1 virus. However, 5 of 37 "immune" persons developed poliovirus infection. Virus and pre-existing antibody were of same type. Sex distributions among the infected were similar for the 2 viruses at all ages. No significant association could be found between either type of virus infection and any type of illness. However, serological rises to ECHO-1 virus in sera from 2 patients from this military base suffering from aseptic meningitis support the possibility that ECHO-1, like ECHO-6 and perhaps others, may occasionally cause aseptic meningitis.