The sera of residents of two tropical sites were examined for the property of neutralizing the poliomyelitis virus. Seven of 9 adults of Thursday Island, Australia, and 10 of 12 adults of Formosa, Brazil, possessed this property. In the former place sporadic cases of poliomyelitis occur, and deaths from the disease have been reported from scattered parts of Brazil.
These and similar findings in other regions where poliomyelitis epidemics are infrequent suggest a wide distribution of the virus and disease, a generalized immunization of the residents to the virus, and an effect of warm climate on the occurrence of epidemics.
If the neutralization test is a specific antigen-antibody reaction, the ability of human sera from scattered areas to neutralize the same standard strain of virus speaks for a common antigenicity of the virus in the regions studied.