An indisposition to do anything, or to be anything; a total deadness and distaste, a suspension of vitality;... an ossification all over; an oyster-like insensibility to the passing events; a mind-stupor; a brawny defiance to the needles of a thrusting-in conscience. —Charles Lamb
The victims of influenza are less articulate than Charles Lamb, but at this moment there are thousands of them, the world over, who have recently experienced the hang-over which is so characteristic of this infection, and thousands more will do so before this strange disease again retires to its normal level of incidence.
In discussing the health of our army, General James S. Simmons stated that respiratory diseases were the most troublesome in the last war and that influenza must still be considered one of the most formidable "disease enemies" of the soldier. Many of us this winter were reminded of the world outbreak of flu in the winter of 1918-1919: in this country alone there were then more than 20,000,000 cases resulting in about 430,000 deaths in less than six months.
During the present war England had to cope with the urgent problems of acute respiratory infection in overcrowded air-raid shelters and in factories; now these dangers are our concern wherever they are met in camps, schools, industrial concentrations, transports, or public carriers. The possibility of recurrent epidemics, perhaps of increasing virulence, even of another pandemic, must be faced.
Although influenza is still far below its 1918-1919 level, we must not be complacent. Some signals are flying. The number of influenza cases. 82,951, reported by our State Department Health for the week ending December 18, 1943, was more than three times greater than the previous week and more than twenty-seven times that of the corresponding week in 1942. While the fight goes on, let us consider what advances have been made since 1918-1919 in the prevention and treatment of influenza and its ally, pneumonia.
A comparison of what was known then with our present knowledge reveals that we have made amazing progress. It was generally believed in 1918 that influenza and all of the pneumonias were of bacterial origin. The viral nature of epidemic influenza was first established in England in 1933, but t was not until 1938 that "virus pneumonia" was clearly recognized. Thus we are across the frontier of explorations that promise to push the range of medical knowledge at least as far as did the pioneer bacteriologic investigations of the last century.
What is meant by the viruses? To most people they are as mysterious as spells of primitive magic. In 1935, Wendell M. Stanley isolated the crystalline protein which is the tobacco virus. Here are substances which seem to stand on the dividing line between the animate and the inanimate, and as more is known about them our whole concept of "life" may well be changed. The fact that to "live"—that is, to multiply —viruses must be associated with living cells is of fundamental importance in our treatment of viral infections. Much of the mystery of the viruses may be attributed to their smallness. While learned theologians used to argue about how many angels could stand on the head of a pin, today it is the size of the viruses which absorbs those scientists who are competent to take such minute measurements by means of the electron microscope. To gaze upon the photograph of an influenza virus stirs the philosophic biologist to a deeper awe of nature and to a sharper impulse to investigate the laws which must control these atomies.
Influenza exists in three forms: the world-sweeping pandemics such as that of 1918-1919, the epidemics such as we are now passing through, and the low-grade, constantly present or endemic form. It is from studies of epidemic influenza that the greatest progress has been made. It is plainly wrong to consider the flu as a war disease, although, as Edward Francis has noted, when virulent influenza coincides with the cruel shifts of population caused by war, the disease rises sharply.
What happens between epidemics is still a mystery. Richard E. Shope has discovered that the closely related virus of swine influenza can remain infective in the earthworm for as long as thirty-two months. Christopher H. Andrewes has suggested that human influenza viruses may have a basic, harmless form, in which they are harbored in human carriers and from which they become virulent. It is recognized that epidemics tend to recur every other year and that the present wave is not an example of spontaneous generation, but the continuation of what appears to be a cyclic pattern. This cycle has frequently run a course of thirty-three weeks. What effect the substitution of transcontinental and transoceanic aviation for caravan and ship will have on this cycle remains to be determined.
Until much more is known, "influenza" includes at least three types of infection, all of which present the same symptoms. The first of these is the catch-all, "acute febrile catarrh," from which the term "cat fever" is derived. This includes the influenza-like diseases from which specific viruses have not yet been isolated. The second form is influenza A, traceable to the specific virus isolated in England in 1933 or to related strains. It is this virus which seems to be largely responsible for the present epidemics and which is so widespread that it has been identified in England, in Martinique, in Minnesota, and in army cases in Michigan. The third form is influenza B, also due to a specific virus; this virus was isolated in New York State in 1940 and then traced back to a California epidemic in 1936.
Both of these viruses, A and B, are of world-wide distribution, but are apparently unrelated; both can cause epidemics, and alone or together they might cause a pandemic. Except for the fact that influenza A is often more severe than influenza B, their differentiation is important to the victims of the disease mainly from the point of view of immunity, since one apparently offers no protection against the other.
Epidemic influenza is characterized by its sudden appearance and rise to a peak in three or four weeks, followed by a prompt subsidence from six to eight weeks after the onset. Although from 10 to 40 per cent of a population may be attacked, the mortality is low. Important in its spread are not only the frank cases of obstinate people who refuse to go to bed, but also persons who are in the incubation period and who innocently remain at large, and finally the cases of "subclinical" infection—that is, of victims who have the disease like "walking typhoid." Such persons can spread the infection and may include as high as one fourth of the population. Convalescent carriers may also be important, but the concert coughers, however high their nuisance value, may be relatively innocuous.
Now what steps can be taken to prevent influenza? Avoidance of exposure is preached but too seldom practiced. Crowded trains, streetcars, and buses—here is the environment in which respiratory infection flourishes. While thousands of civilian workers and members of the armed forces are forced to take this risk, anyone who feels a cold coming on and has an ivory tower available should stay in it.
Two types of vaccination against influenza are being studied. In one of them the vaccine is put under the skin. In the other it is applied to the mucosa of the respiratory tract to increase resistance at the local barrier which the virus must pass to cause infection. Extensive trial of this type of vaccination has been made among Australian troops and in Russia. In general it may be said that vaccination against influenza is still in the experimental stage and that, while it may not prevent infection, it may modify the course of the disease to a milder form with fewer complications.