Beschreibung:
A technique is developed by which minimal changes in haemagglutinin inhibitors can be detected.It is shown that theinhibitor indexof normal human nasal secretions is 33·2 with a standard deviation of ±7·4. This value is independent of the donor, of the absolute amount of mucus collected, of the time of extraction, and of the period of storage.Minimal amounts of influenza viruses (less than one agglutinating dose) are capable of causing significant alteration in the inhibitor index upon interactionin vitrofor 60 min. at 37° C.