STUDIES OF THE DISTRIBUTION OF POLIOMYELITIS VIRUS : V. THE VIRUS IN FAMILIAL ASSOCIATES OF CASES

Relationship between serum antibodies and subclinical infections with poliomyelitis virus

Three families in which cases of poliomyelitis had recently occurred were studied for the extent of subclinical infection and the presence of serum antibodies to both the mouse-adapted Lansing strain and the specific strain of poliomyelitis isolated from members of the family. Virus was recovered from the stools of all 5 cases and from 8 of 17 familial associates at the time of the first collection of specimens. Only two of the associates were still carrying virus 3 weeks later. The individuals from whom virus was recovered were younger than 11 years of age with two exceptions, one of them a frank case. Antibodies to the mouse-adapted Lansing strain of poliomyelitis virus were demonstrated in the sera of every person 11 years of age or older but in none from individuals under this age with the possible exception of one whose second specimen was weakly positive. Antibodies for the specific agent isolated from each family were likewise found at the beginning of the study in every person over 11 years of age but also in 4 of 9 under that age. The neutralization indices of sera of the second collection were generally higher than those of the sera collected soon after the disease occurred in the family, reflecting the antigenic stimulus of the "family" viruses. The inverse relationship of demonstrable antibodies to virus isolations strongly suggests that the presence of serum antibodies is effective in limiting subclinical infection with poliomyelitis virus. The question of cross-immunity in protection against infection with poliomyelitis virus is discussed.

The development of homologous neutralizing antibody during a Type 1 poliomyelitis epidemic

1. Sera taken from seventy-nine individuals who had been examined for poliomyelitis antibodies shortly before a Type 1 epidemic, were examined for the development of antibodies to polio-virus 6 months after the epidemic.

2. Ten of eleven (91%) susceptibles aged 5–7 years, 44% of those aged 8–9 years, 25% of those aged 10–14 and only one of fifteen (7%) 15 years or more old had developed neutralizing antibodies to Type 1 polio-virus.

3. In the school which the younger subjects attended, one boy developed paralytic poliomyelitis while the school was in session, but the amount of minor illness in the epidemic period was not significantly different from the 3-year average.

4. The comparison between these findings and the notification rate for the province suggested that the chance of an infection with polio-virus during this epidemic, leading to a clinically recognizable attack of the disease, might have been as much as eighteen times higher in adolescents and adults than in the 5–9 age group.

5. The epidemiological significance of these results is discussed.

We have pleasure in acknowledging our indebtedness to Dr J. H. S. Gear for the report on the sera collected before the epidemic, to Dr W. Murphy, Medical Officer of Health, for data about notifications, to Dr A. M. Douglas for assisting by collecting some of the bloods, to the Principal and staff of John McGlashan College for their readiness to assist us at all times and to all those subjects who allowed us to take a further specimen of their blood for this investigation.