A mild epidemic occurred in 1874 in Berlin.
Influenza prevailed over a wide area in the United States during the early months of 1879. The characteristics of this visitation have been well described by Da Costa.15
15 "The Prevailing Epidemic of Influenza—Its Characteristic Phenomena—Pulmonary, Gastro-intestinal, Cerebral, and Nervous—Its Wide Distribution, Mortality, and Treatment," Medical and Surgical Reporter, Philadelphia, March 8, 1879.
The disease, since the great epidemic of 1847-48, has affected a smaller proportion of the inhabitants of the localities visited, and has run a less dangerous course, than in the earlier epidemics. It has for this reason occupied a less conspicuous place in the medical literature of recent years. It is nevertheless true that even in the mildest epidemics, when a relatively small number of persons are seized and the symptoms are in most cases almost insignificant, cases do here and there occur which are of a serious or even fatal character, and that the death-rate from other diseases is for the time considerably increased.
Catarrhal affections have often prevailed among the domestic animals when influenza has been epidemic. Horses, dogs, and cats are subject to these disorders; neat cattle, goats, and sheep have been less commonly affected; chickens and pheasants have suffered, and it is stated by some of the older writers that birds, and particularly the sparrow, have deserted localities in which influenza was prevailing, and that migratory birds have taken flight earlier than usual.
These epizoötics have sometimes preceded the appearance of influenza among men by a period of some weeks or days; in other instances they have appeared at the same time; and in a widespread outbreak among horses in the United States in 1872, in which the symptoms and morbid anatomy, accurately observed, were undoubtedly those of influenza, the disease did not affect man except to a very limited extent. A want of fulness of description, and the inaccuracy of diagnosis too common in the consideration of the general diseases of the lower animals, leave the precise nature of most of the epizoötics described by the earlier writers doubtful.
An extensive influenza of moderate intensity prevailed as an epizoötic, chiefly affecting horses, during the latter part of the summer and the autumn of 1880 in Canada and the United States east of the Mississippi River. Dogs were also affected, but less generally, and human beings to a still slighter extent. In several localities where this invasion was observed by the writer the horses were first affected, the dogs next, and after the lapse of some weeks, as the animals were recovering, the disease became epidemic; but those persons who took care of horses and were much in contact with them neither suffered earlier nor more severely than others not so exposed.
ETIOLOGY.—1. Predisposing Influences.—There are no well-established facts pointing to the existence of individual peculiarities that can be regarded as predisposing influences. When the disease appears a large proportion of the population is attacked without distinction of age, sex, social condition, or occupation. Previous illness, whether acute or chronic, local or constitutional, affords no protection. Aged and infirm persons and those of nervous temperament are peculiarly liable to attack, but the robust possess no immunity. All races and dwellers in every climate are the victims of influenza. In a community invaded by the disease females are apt to be the first attacked, adult males next, and children last. It has been observed that in some epidemics children are but little liable to contract the disease.
An attack confers no exemption from the disease in another epidemic, and independently of relapses, which are not infrequent, persons have been known to experience a second attack during the prevalence of the same epidemic.
Persons dwelling in overcrowded and ill-ventilated habitations and in low, damp and unhealthy situations have, in certain epidemics, especially suffered, and the increase of deaths by influenza is proportionately much greater in districts in which there is ordinarily a high mortality than in healthier places.