Influenza

The most universally employed measurement of the impact of epidemics and pandemics is the excess of mortality due to influenza and pneumonia. Other criteria are absenteeism from school and work, and all three will show positive indications when epidemics are of substantial size. During the 1974-1975 influenza season in Houston, school and industrial absenteeism and the increase in influenza and pneumonia deaths, despite a newly devised statistical procedure, did not signal an epidemic. However, a system of community surveillance of febrile respiratory illness with cultures for influenza virus during late January and early February 1975 gave unmistakable evidence of an influenza epidemic, with more than 600 virus isolations and an estimated occurrence of 50,000 cases of the disease. It is believed that this type of study can explore facets of the epidemiology of the disease not hitherto adequately examined. From this surveillance, which will continue through the summer months, it is hoped to gain further knowledge of the occurrence of antigenic drift and shift, and of the details of the early origin and progress of epidemics. Current speculation is that there will be another world pandemic before 1980 caused by a derivative of A strains presently circulating; in 1985-1991, a pandemic is predicted to be caused by a virus antigenically related to the swine agent of 1918. The purity of vaccines has been increased in recent years through ultracentrifugation and high-efficiency filtration, so that dosages can be increased while severity of reactions is reduced. The current level of dosage of vaccine for adults is 1200 chick cell agglutinating units, almost double what it was a dozen years ago. Recently, vaccines have been prepared more rapidly by the use of viral recombinants that incorporate the surface antigens of newly emerged epidemic strains into the core of older strains that grow well in embryonated eggs. This practical device greatly reduces the lead time in the preparation of new vaccines. The main problem in immunization against influenza is the need to reimmunize every 1-3 years. This creates an enormous requirement for vaccine and therefore a problem of selection of recipients. Currently, it is recommended that aged persons and those with cardiovascular, pulmonary and other chronic illnesses should receive the vaccine. Pregnant women are not more susceptible than others to the disease, and they should receive vaccine only if they have some other indications for immunization. Schoolchildren probably are important in transmission of the disease, but at present there is no special recommendation to immunize them. Young children occasionally have severe febrile convulsions when immunized against influenza, and those with this history probably should not be immunized. Amantadine is useful as a prophylactic agent in A(H3N2) influenza infections, and several reports suggest therapeutic benefits as well. Its benefits probably have not been fully utilized...