In addition to this means of inter-communication we had the possibility of spread to the various camps by the ordinary course of civilian and commercial travel as in spread to different communities, and also the possibility of importing large amounts of virus at one time on the incoming trains with new draft troops.
Soper gives the following order for camps attacked:
| Order. | Camp. | Location. | Date. |
|---|---|---|---|
| 1 | Devens | Massachusetts | Sept. 12 |
| 2 | Upton | New York | Sept. 13 |
| 3 | Lee | Virginia | Sept. 17 |
| 4 | Dix | New Jersey | Sept. 18 |
| 4 | Jackson | South Carolina | Sept. 18 |
| 5 | Hoboken | New Jersey | Sept. 19 |
| 5 | Syracuse | New York | Sept. 19 |
| 5 | Gordon | Georgia | Sept. 19 |
| 5 | Humphreys | Virginia | Sept. 19 |
| 6 | Logan | Texas | Sept. 20 |
| 6 | Funston | Kansas | Sept. 20 |
| 6 | Meade | Maryland | Sept. 20 |
| 7 | Grant | Illinois | Sept. 22 |
| 7 | Taylor | Kentucky | Sept. 22 |
| 8 | Sevier | South Carolina | Sept. 23 |
| 8 | Lewis | Washington | Sept. 23 |
| 8 | Newport News | Virginia | Sept. 23 |
| 9 | Pike | Arkansas | Sept. 24 |
| 10 | Beauregard | Louisiana | Sept. 25 |
| 10 | Eustis | Virginia | Sept. 25 |
| 11 | Greene | North Carolina | Sept. 26 |
| 11 | McClellan | Alabama | Sept. 26 |
| 12 | Kearney | California | Sept. 27 |
| 12 | Bowie | Texas | Sept. 27 |
| 13 | Johnston | Florida | Sept. 28 |
| 13 | Sheridan | Alabama | Sept. 28 |
| 14 | Sherman | Ohio | Sept. 29 |
| 14 | Dodge | Iowa | Sept. 29 |
| 14 | Shelby | Mississippi | Sept. 29 |
| 15 | Custer | Michigan | Sept. 30 |
| 16 | Travis | Texas | Oct. 1 |
| 17 | Cody | New Mexico | Oct. 3 |
| 18 | Forrest | Georgia | Oct. 6 |
| 19 | MacArthur | Texas | Oct. 7 |
| 20 | Wadsworth | South Carolina | Oct. 11 |
| 20 | Wheeler | Georgia | Oct. 11 |
| 20 | Greenleaf | Georgia | Oct. 11 |
Howard and Love have established definitely that the extension of the virulent influenza from Camp Devens to other camps south and west in September, 1918, can be traced in many instances directly to the interchange of military personnel from infected to non-infected camps. The height of the September outbreak in the United States Army extended over a period of about nine weeks, from Sept. 13th to November 15th, and during this period over 20,000 deaths occurred among troops in the United States alone in excess of the number that would have occurred, if the disease death rate for the corresponding period of the preceding year had prevailed.
It is interesting to note with respect to Camp Humphreys, Virginia, that there were possibly some sporadic cases previous to the autumn outbreak. Brewer in reporting on the epidemic in September and October records the first case as having occurred shortly after July 1st. He makes no mention of there having been any outbreak whatever prior to that date. Between July 1st and September 12th there were only sporadic cases diagnosed as influenza. The autumn outbreak began at Camp Humphreys September 13th and ended October 18th.
Recrudescences.
We have already seen from the work of Pearl that recrudescences following the original spread in any one locality were the rule rather than the exception in this country. He found that in sixty-five per cent. of the forty cities studied there were two distinct peaks in the mortality curve and in twenty per cent. there were three, while only fifteen per cent. had but one peak. The first peak was as a rule the highest. Although there was no absolute regularity in the time of occurrence of the recrudescences, Pearl established that the high peak cities had the second peaks on an average 7.1 weeks after the first, and the third peak on an average 13.1 weeks after the second. The two-peak cities are divided into two classes, the first comprising about a third of the total number, had the second mortality peak around eight weeks after the first, while the remaining two-thirds had the second peak about thirteen weeks after the first. The cycle in the epidemic wave appears to be nearly a multiple of seven weeks. He suggests that the smaller group of two-peak cities with early second peak may have been cities which at the time were presumably destined to show a third distinct wave and peak of mortality, but in which for some reason not now apparent the third wave did not eventuate. In contradistinction the larger group of two-peak cities with the second peak occurring around thirteen weeks after the first are presumably cities in which the complex of factors determining the form of the mortality curve was such as to lead definitely to a two and only two-peak curve. In three-peak cities the first interval was around seven weeks, the second around thirteen weeks. The two-peak cities with an interval around thirteen were probably not destined, according to Pearl, to have another repetition, but those with an interval of seven were presumably destined to have a second interval, the thirteen-week interval, which for some reason did not occur.
This raises the question of periodicity, a subject which we will discuss at a more appropriate place.
This experience of recrudescences was similar in the American Expeditionary Forces. The first outbreak lasted through April and May and into June. The second came in September and October. The spring epidemic had been characterized by mildness and was known as three-day fever, but in the autumn, complications of the respiratory tract predominated in the symptom complex. By August 18th a severe epidemic had occurred in an artillery camp at La Valdahon in the Jura Mountains, near Bezançon. Early in September a larger epidemic occurred in an artillery camp near Bordeaux. The epidemic in our troops in France, as well as in the French civil and military population, reached its height during October. The Service of Supply was more heavily affected than were the troops situated on the battle front. The morbidity rate appeared to have been almost the same as that in the United States. That it was not quite as high has been shown by Howard and Love. Longcope states that it prevailed particularly among the troops at the base ports where during a part of the epidemic transports laden with infected troops were being landed; in those organizations which contained the largest number of replacement troops; and in organizations being moved on troop trains, where the men were necessarily closely crowded.
The second outbreak subsided during the early part of November. A third occurred in January and February, very much as it had done in the United States. In the interval between the second and third recurrences there was no time at which the entire Expeditionary Forces were free from the disease. The author had occasion to study an outbreak occurring early in December in the 26th Division stationed in rest area at Montigny-le-Roi. In this outbreak the respiratory complications predominated, as in October, and the mortality was comparatively high. We had had occasion to study the same disease at Camp Sevier, South Carolina in September and early October, 1918, and in two different localities in France in December, 1918, and February, 1919, and found that the clinical characteristics were identical on both continents.