Serological Studies on Influenza during a Nine-month Period.

The anticipated influenza B epidemic materialized late in November, 1945 and reached its peak during the month of December. Sporadic cases were recognized in the United States (1) for a period of some months preceding the actual epidemic. The importance of recognizing this preepidemic period is unquestionably a necessity in order to avail ourselves of the prepared vaccines. It has been demonstrated (2-12) that immunization against the influenza viruses elicits an antibody increase and offers protection to the experimental inhalation of the virus strains. Francis and coworkers (13) have demonstrated further that vaccination with inactivated influenza viruses Types A and B offers protection against influenza B during an epidemic., That this epidemic was due to Type B has also been shown by Dalldorf and Rice (14). It is recognized that other agents are responsible for certain cases of bacteria-free pneumonias. Clinically these various types of virus pneumonia often resemble each other. It is essential, therefore, to determine, if possible, the agent responsible for the infection. Their differentiation may be made by isolation of the virus or by serological studies. In many instances, failure to isolate an organism does not eliminate its possible role as causative agent. On the other hand, the development of specific antibodies in convalescent sera is one criterion that is considered to be conclusive evidence of contact with the specific antigen. Many agents have been isolated and serological technics for their identification have been developed. These various viral technics available for laboratory diagnosis are now routinely employed in many laboratories. The examination of serum samples for the presence of antibodies to viruses, as well as those producing a clinical syndrome