O NCE more we are in the midst of an epidemic

of what is called influenza. True influenza is a disease of quite definite characteristics, but these are resembled fairly closely by the symptoms of certain other diseases, and complications so frequently change the picture that it is not always easy to decide whether a case is one of influenza vera or not. In the case of widespread and severe epidemics it is fairly easy to make a diagnosis, but in the sporadic cases and in the small localized -outbreaks it is more difficult to form a ciefmite decision.

THE HISTORY OF THE DISEASE.

Great outbreaks -of what seems to have been influenza occurred in ancient times. Diodorus Siculus mentions an epidemic in the Athenian army in Sicily in 415 B.C. which from its -description was not unlike the recent outbreak of 191& The epidemic of 412 B.C. described by Livy and Hippocrates is also believed to have been influenza. In the descr4otion of these epidemics his- torians have generally exaggerated the deadliness of the disease, as indeed any non-medical historian of the 1918 visitation might easily do.

In A.D. 827 an attack of cough which spread like a plague occurred, and in 876 an epidemic began in Italy and later affected the whole of Europe. In 976 there was -an epidemic in France and Germany, and new visitations occurred in E-urope from time to time, but the first clearly described epidemic took place in 1510. Since that time there have been fourteen very widespread outbreaks. There was another group of -less extensive epidemics ; and finally there have been ten periods when relatively small areas have been visited.

The modern study of influenza dates from the 1889 visitation, and innumerable volumes and papers have been devoted to the subject, one of the best being a monograph by Warren T. Vaughan published in America in 1921.

THE METHODS OF INFECTION.

The spread during an epidemic is quite characteristic, the disease being communicated only from person to person. This was well illustrated in the outbreak in New South Wales in 1918-19. At first the few sufferers were carefully isolated at the quarantine hospital, but as soon as the precautions became a little lax the epidemic spread with dreadful rapidity and high mortality among the people. Then the authorities wisely closed theatres, schools, universities, &c., and for a time even forbade church services unless held in the open air with each seat some feet away from its neighbour. That this last precaution was not unnecessary is evidenced by the fact that in San Quentin Prison it was observed that there was always a larger number of cases on Tuesdays and Wednesdays, as a result of attendance at the prison cinematograph performance in a small auditorium on Sundays.

The actual path of infection from one person to another is unknown. It is thought that the infecting agent leaves the body in the spray of coughing or talking, and may be carried on inanimate objects such as a glove, or on eating utensils that have been improperly cleaned. It is significant that among 17,000 persons who ate from machine-washed dishes the frequency of influenza was only one-fifth as great as that among four thousand who ate from hand-washed dishes, other circumstances being approximately equal.

It is probable, but not certain, that persons who are themselves unaffected may transmit the disease, and that it is frequently propagated by convalescents, and by contaminated food.

The incubation period varies from twenty-four to sixty hours, averaging about forty-eight. Anything that lowers the resistance renders one more susceptible to infection with influenza—especially cold, fatigue, hunger, or illness due to some other cause. The early cases in an epidemic are generally mild with few respira- tory complications (bronchitis or pneumonia) and low mortality. Later in the epidemic the virulence of the disease becomes greater, bronchitis and pneumonia are much more frequent, and the percentage of deaths increases notably.

SOME POSSIBLE ORIGINS OF EPIDEMICS.

There are several hypotheses as to the origin of influenza, of which the three following are the most important :- (1) Influenza is always present in one particular part of the globe—apparently, Turkestan. At intervals it somehow becomes more virulent and spreads widely. After such a, pandemic there occur scattered local out- breaks for a few years, but these disappear after a time. The majority of local outbreaks occurring between great epidemics are not true influenza.

(2) The same as (1), but there is considered to be more than one place in the world from which great epidemics may spread.

(3) Influenza is distributed over the earth—i.e., it is always present in many localities. Frequently, in one or another of these spots, it somehow acquires increased virulence and starts a smaller or larger epidemic. Some- times these epidemics become so widespread as to form a pandemic.

Dr. Brownlee has done much interesting work on the periodicity of influenza. He observed that epidemics are apt to recur at intervals of thirty-three weeks, but that if the epidemic falls due between the end of June and the beginning of December it is unlikely to occur, while if it falls due between December and the end of May it will almost certainly occur. Whether this periodicity is accidental or whether it is due to some peculiarity of the organism causing the disease is unknown. Dr. Brownlee was able correctly to forecast the occurrence of an outbreak in the early months of 1920, and the present epidemic which began in the second -.yeek in January was also correctly forecasted—the latter was twice thirty-three weeks from the winter outbreak of October, 1923—January, 1924. Thirty-three weeks be- fore that there was the mild outbreak of February— March, 1923, and twice thirty-three weeks before that occurred the severe epidemic of the winter 1921-22.

It is interesting to note that bronchitis and pneumonia, the complications which render influenza epidemics so dangerous, seldom become prevalent unless the tempera- ture of the earth four feet below the surface has fallen below 47° Fahrenheit. In this country this temperature is generally reached in December and so influenza epi- demics occurring after Christmas are much more likely to be complicated and severe than those before Christmas.

Avoidance of fatigue, hunger, cold or other resistance- lowering agencies will diminish one's liability to infection, and when once one has become infected rest and warmth Are the main curative agents. Here at the moment our knowledge ends. Intensive study of this disease, -which has been described as "by far the most serious scourge with which our modern world is afflicted" is progressing in every civilized country, and it is hoped that some definite result will be attained in the near future.

NORMAN HAIRE.