INFLUENZA. The word is derived from the Italian influenza di freddo, influence, ef fect of cold. The other common name is grippe or grip, from the French agripper, to at tack, or from gripper, to grip. The French name dates from 1712. Influenza is a febrile affection involving the respiratory tract often est, but attacking almost any set of tissues, es pecially the mucous membranes. It usually oc curs as a pandemic, that is, an infection spread ing to every people. It has been seen as a pan demic often since the early 16th century and there are accounts of it before. The epidemic of 412 a.c., mentioned by Hippocrates and Livy, is considered to have been influenza. The first American epidemic was in 1647, when some 6,000 deaths occurred in the Barbadoes and Saint Kitts. Cromwell is said to have died from it some 10 years later. There were four pandemic influenza periods in the last century — 1830-33; 1836-37; 1847-48; and the one re called the best, that of 1889-90. This began in Turkestan in June 1889. By the end of the year it was as far west as the Pacific. It crossed the Pacific to rage in India the follow ing spring and in a year and a half it had circled the globe. The disease probably always origi nates in the East at a time when crowded popu lations are suffering from want and therefore lack resistive vitality against the specific mi crobe which gains in virulence as the result of having such favorable material to multiply in. The affection usually attracts the attention of the medical world in some European country intimately in touch with the East. It rages with virulence and receives as an epithet the name of that country for a time. The epidemic at the end of the 19th century, first noted in Russia, was for some time called Russian in fluenza. The epidemic of 1918-19 was, for a similar reason, called Spanish influenza.
The duration of the disease in any locality is usually under two months. There is probably no disease which attacks so large a proportion of the inhabitants of infected territory. Often one-fourth, sometimes even more than one third, of the population catch the disease. Un like most other diseases, adults from 20 to 40 suffer most. Infants are almost immune; the old, particularly if they have gone through a previous epidemic, seem to be protected to a great extent. Some protection is undoubtedly afforded by a previous attack, though a few persons seem to be thus predisposed to subse quent attacks. The mortality of uncomplicated influenza is low. In the German army in 1889 9Q, out of some 60,000 cases the mortality was not more than one-tenth of 1 per cent. The
deaths from pneumonia and other complica tions make the disease serious. Most of the deaths during an epidemic are due to pneumo nia. The disease is much more fatal at the be ginning of the epidemic in any locality and deaths may take place even in strong, young, healthy adults, within two or three days after the first symptoms are manifest. The index that the epidemic is about to wane is that the disease becomes much less severe in its symp toms and less fatal. It is usually not until after this that the number of patients attacked be gins to reduce and then the mortality drops rap idly. The latest epidemic followed all these rules rather closely.
The cause of the disease is not known for certain. The so-called influenza bacillus, found by Pfeiffer (1892), is practically always pres ent in the disease and is considered by a great many good authorities to be the cause, but the etiology is not definitely settled. Other micro organisms supposed to be concerned in the causation of special epidemics have been de scribed, notably a filterable virus, that is, a mi crobic agent so small that it passes through the pores of a laboratory filter, but this has not been confirmed with any degree • of certainty up to the present time. The presence of this agent was noted in many cases during the re cent epidemic. The disease does not spread through the air but is a true contagion requir ing for transmission contact, direct or indirect, with an individual suffering from the disease. The bacillus of Pfeiffer has been found in a very great many cases in large numbers in the secretions of the nose, throat and lungs, though the supposition that it must produce catarrhal symptoms, running from the eyes and nose, has not been confirmed in the present epidemic. It is found to exist luxuriantly in the back of the throat, growing in and between the cells and being distributed from here through the body to produce the respiratory or gastrointestinal symptoms. The infection may readily occur therefore from the hands in eating, and one of the most important precautions against the dis ease is thorough cleansing of the hands before meals. The bacillus may be scattered around for considerable distances by coughing or sneezing, so that it is important to insist on the use of a handkerchief, or still better, of some waste cotton material or soft paper that can be burned, to be placed before the nose and mouth during sneezing and coughing.