Recurrences in Winter of 1919–1920.
We distinguish between the flareups following the autumn spread of 1918, and which lasted until the spring of 1919, and yet another widely distributed recurrence in the winter of 1920. We have called the former recrudescences to distinguish them in point of time from the latter, but do not imply thereby any difference in the character or origin of the secondary waves. Between them all there occurred almost continuously isolated or solitary cases of influenza which served to keep the fires smouldering. In our own work in the city of Boston we found record of scattered infrequent cases of clinical influenza of apparently low infectivity in every month from March, 1919, until the recurrence in January, 1920.
Moreover, in some localities there were during this interval small epidemic outbreaks. Thus a report from Lisbon, Portugal, on June 1, 1919, states that the deaths from influenza in that city during the preceding two weeks had been more than the total deaths from all causes during the preceding four months. A report from London, October 30, 1919, states that during the preceding few weeks there had been in the ninety-six great towns of England and Wales a slight but gradual increase in the number of deaths attributed to the disease, and a coincident rise in the number of notifications of acute primary and acute influenzal pneumonia. The feeling at that time was that the increase was associated with prevailing meteorological conditions, and did not apparently signify more than the usual variation in respiratory diseases which was to be expected at that season of the year. On November 3, 1919, the disease was reported prevailing at Chile and it was spreading throughout Bolivia. At the same time influenza had spread over the entire country surrounding Buenos Ayres and had even reached the neighboring city of Montevideo. In the latter part of November more than 2,000 cases had been reported at Lemaies, about fifteen miles northeast of Granada, Spain.
The winter of 1920.—In the United States the death rates from influenza and pneumonia in the large cities over the entire country were below the usual average from May, 1919, until January 1, 1920. In the week ending January 17th there was a sharp increase in the influenza-pneumonia rate, which occurred simultaneously in Kansas City and Chicago. In the latter city an excess over the average was not reached until some days later, but the maximum mortality occurred in the week ending January 31st, while in Kansas City the mortality did not reach its height until one week later. New York, Washington, San Francisco, Milwaukee and St. Paul soon followed with an increase in the week ending January 24th, and in the subsequent two weeks many other cities were added to the list. By February 14th thirty-two out of the thirty-six large cities reporting had an increase in the death rate from influenza and pneumonia as compared with the same period in 1917. The maximum was reached at this time, and according to the Bureau of the Census reports there were 7,059 deaths from influenza and pneumonia during the week ending February 14th. In the next week the number of deaths from these causes in the cities reporting had dropped to 5,088. The February weekly average for 1917 was 1,489. In the week ending February 14th, 267,643 cases of influenza were reported from forty-one states; the excess annual death rate as compared with the average for the period from 1910 to 1916 was 1,319.
In general the 1920 recurrence was decidedly milder than the autumn outbreak of 1918. Certain cities, however, suffered severely, particularly Detroit, Milwaukee, Kansas City, Minneapolis and St. Louis. In these the death rate, while the epidemic lasted, was higher than that of 1918. The duration of the epidemic was generally, however, shorter in these cities. Columbus, Ohio, and Indianapolis suffered severely, but to a less extent than the cities just mentioned. In Chicago the death rate was not as high as in the fall of 1918, but it did rise far above the point reached during the 1889–90 outbreak, and the influenza in the last two weeks of January brought the total mortality for that month up to 5,149, the highest mortality in the history of the city with the exception of October, 1918.
We have already discussed the recurrent epidemic as it was studied in Detroit. The salient characteristics were a rapid and fairly symmetrical evolution, a shorter duration than in 1918, a lower morbidity with a higher mortality rate, and finally, a smaller total number of deaths than in 1918.
The 1920 recurrence was widespread. It was not confined entirely to the large cities. Semi-official reports from small towns and villages show very much the same conditions as were observed in the larger cities. On the whole, however, most communities, both large and small, suffered less severely than in the first spread. The few exceptions to this were distributed over the continent without uniformity.
The first among the large cities to show an increase in death rate from the epidemic was Kansas City, in which the mortality first climbed in the week ending January 17th. The following week there was an increased rate in Chicago, New York and Milwaukee, and one week later, Boston, Detroit, San Francisco and Philadelphia were affected. New Orleans was one of the last large cities affected, not showing a definite increase until the week ending February 14th. In contrast to the 1918 pandemic, the influenza of 1920 showed no clearcut direction of spread, and was as in the years following 1889 due, without doubt, to firing up of the pandemic virus as it had been left scattered in many endemic foci throughout the earth. There probably were instances of spread from the larger centers to outlying districts, but there was no continuous spread over large areas. The accompanying table shows clearly that the disease this year commenced in the center of the continent, a fact which would seem to disconnect it entirely from the late epidemics of 1919, occurring in Europe:
| Annual death rates from all causes by week in certain large cities of the United States from week ending January 3d to week ending February 21st. | ||||||||
|---|---|---|---|---|---|---|---|---|
| City. | Week Ending | |||||||
| January. | February. | |||||||
| 3 | 10 | 17 | 24 | 31 | 7 | 14 | 21 | |
| Kansas City | 16.3 | 15.8 | 19.3 | 32.7 | 39.5 | 61.5 | 44.0 | 29.1 |
| Chicago | 14.4 | 13.8 | 15.1 | 23.5 | 41.3 | 39.1 | 24.6 | 17.7 |
| New York | 14.0 | 15.3 | 14.6 | 19.5 | 28.0 | 35.0 | 35.1 | 24.8 |
| Milwaukee | 11.6 | 12.5 | 9.0 | 15.6 | 29.4 | 34.5 | 27.1 | 16.9 |
| Detroit | 13.7 | 13.0 | 14.2 | 15.5 | 33.9 | 60.9 | 42.9 | 21.6 |
| Boston | 16.8 | 16.9 | 14.1 | 16.8 | 20.3 | 27.1 | 33.7 | 32.1 |
| San Francisco | 16.5 | 15.4 | 19.6 | 19.2 | 22.9 | 25.2 | 31.8 | 28.8 |
| Philadelphia | 15.6 | 16.7 | 16.2 | 16.8 | 18.3 | 22.1 | 34.3 | 37.2 |
| New Orleans | 18.8 | 19.6 | 22.6 | 18.8 | 20.9 | 20.1 | 25.0 | 32.3 |
The relative severity of the two epidemics in certain of the large cities has been compared by H. F. Vaughan, and he has found as is seen by the table that Kansas City and Detroit, two of the early cities affected, had the highest mortality in 1920. Philadelphia in 1918 lost nearly three times as many people as Detroit did in 1920. Detroit was higher than Chicago in 1920, but lower in 1918.
| Per cent. of population killed by influenza. | |||
|---|---|---|---|
| 1920. | 1918–1919. | ||
| First seven weeks. | First seven weeks. | Twenty-one weeks. | |
| Detroit | 0.20 | 0.17 | 0.28 |
| Chicago | 0.12 | 0.34 | 0.41 |
| Kansas City | 0.24 | 0.30 | 0.63 |
| Philadelphia | 0.10 | 0.76 | 0.82 |
| New Orleans | 0.05 | 0.55 | 0.77 |
The following table taken from the “Final Influenza Bulletin,” by E. R. Kelley, Commissioner of Health in Massachusetts, shows distinctly the difference that must be always borne in mind between curves of influenza incidence and death curves. In his table the mortality climbed first on the week ending January 13th, as in the table above, but the increase in influenza cases began at least one week earlier. It is characteristic of influenza epidemics that the rise of mortality curves follows that of morbidity by about a week:
| Influenza and pneumonia cases in Massachusetts in the first three months of 1920. | ||||
|---|---|---|---|---|
| Influenza. | Lobar pneumonia. | |||
| Cases. | Deaths. | Cases. | Deaths. | |
| Week ending January 3d | 41 | 0 | 109 | 9 |
| Week ending January 10th | 46 | 2 | 142 | 50 |
| Week ending January 17th | 58 | 0 | 145 | 52 |
| Week ending January 24th | 489 | 4 | 201 | 56 |
| Week ending January 31st | 4,495 | 48 | 313 | 96 |
| Week ending February 7th | 9,627 | 272 | 382 | 212 |
| Week ending February 14th | 10,747 | 133 | 583 | 140 |
| Week ending February 21st | 5,601 | 181 | 510 | 147 |
| Week ending February 28th | 2,375 | 147 | 313 | 114 |
| Week ending March 6th | 1,144 | 54 | 206 | 34 |
| Week ending March 13th | 490 | 31 | 130 | 54 |
| Week ending March 20th | 254 | 20 | 105 | 44 |
| Week ending March 27th | 147 | 14 | 102 | 94 |
| Week ending April 3d | 218 | 6 | 97 | 12 |
In Massachusetts in the first three months of 1920 there were reported 35,633 cases of influenza and 3,158 of lobar pneumonia, with 906 deaths from the former disease and 1102 from the latter. The case rate per 100,000 from influenza was 883.4; from lobar pneumonia, 78.3; the death rate from influenza, 22.4; from lobar pneumonia, 27.4; and the fatality per cent. from the former disease was 2.5, and from the latter, 34.9.
The epidemics in Detroit and Boston both showed a symmetrical evolution and a single wave. This appears to have been the more frequent type of recurrence in this country. There are examples of the secondary curve. At the Great Lakes Naval Training Station the epidemic began during the week ending January 17th. On January 12th there were fifty-one cases. The peak was reached on the third day with the admission of 182 new cases during twenty-four hours. Although the peak came early the decline was less rapid and there were four secondary peaks, but the outbreak terminated on the twenty-fourth day. On the whole the epidemic was less severe than in 1918. Pneumonia was a complication in about ten per cent. of the reported cases of influenza at the training station.
On the European continent there were similar recurrences in the first three months of 1920. In the large towns of England the recorded deaths from influenza made an increase in a steady curve from sixty-six in the last week of January until the week ending March 27th. After that date there was a gradual falling off. That the situation was in no way as serious as it was at the same time in the American cities and in certain other parts of Europe is indicated by an annotation in the Lancet of March 6th. According to this annotation, the weekly totals of deaths attributed to influenza in London and the 96 great towns had on the whole tended to increase in the early part of 1920, but the absolute increment was so small and the necessary uncertainty of classification so great that no unfavorable inferences could be drawn from these fluctuations alone. On the other hand, the notifications of cases of pneumonia increased appreciably, too much to be set down as a mere chance fluctuation. But notification for this disease had not been in force long enough to enable accurate comparison. There were no indications of epidemic influenza in any of the large factories situated throughout the country. But on the other hand there was proof of the existence of epidemic influenza of an infectious, but relatively non-fatal type in certain large schools situated in the South and Southwest of England.
The annotation concludes that influenza was epidemic in a few localized English and Welsh communities, and that the type was similar to, but less severe than that of 1918–19.
In the city of Paris between the 11th and 31st of January there was a very definite increase in the death rate from inflammation of the respiratory tract above the average for other years.
Renon and Mignot studied 141 cases of influenza (71 men and 70 women) during January and February, 1920, at L’Hopital Necker. Fifteen of the 141 died. According to these observers the grip of 1920 attacked all ages in contradistinction to the 1918 epidemic which affected especially the young and vigorous. One-third of their group were over forty years of age, while some were seventy and eighty years old. In spite of this the disease remained relatively mild. Sixty-four were cases of simple grip. Forty-three had associated bronchitis and pulmonary congestion and edema. Twenty-seven had pneumonia. One had acute pulmonary edema. There were cases of influenza in tuberculosis individuals. One developed an acute serofibrinous pleurisy. One had purulent pleurisy, and one meningitis.
In Copenhagen there occurred between the 18th and 24th of January, 1920, 1,204 cases of influenza with four deaths; in the following week, from the 25th to the 31st of January, 7,445 cases with forty-two deaths; from the 1st to the 7th of February, 11,038 cases with 207 deaths; from the 8th to the 14th of February, 8,308 cases and 327 deaths. This is to be contrasted with the month of December, 1919, in which there were 1,845 cases of influenza in Denmark, of which only 272 were at Copenhagen. In Christiania, Norway, during the week of January 25th to 31st, there occurred eleven deaths from influenza, whereas during the preceding two weeks there had not been a single death from this disease.
In December, 1919, there were reported in Switzerland only 511 cases of influenza. During the month of January, 1920, this increased to 13,162, and in February to 83,008, the estimated population being 4,000,000. From February the disease decreased in prevalence. In Zurich, with a population of 210,000, the epidemic resulted in 14,534 cases. The first increase began around January 4th. The total number of cases for January was 1,071. In February the records of the four weeks showed 2,721, 4,140, 3,341 and 1,899 cases, respectively; in March the decrease was rapid, 886, 442 and 45 cases being reported in the first three weeks. The total number of deaths, mostly due to pneumonia, was 229, a mortality of 1.5 per cent.
During 1920 epidemics were also observed in Valencia, Santander and other towns in Spain, and in Mexico City. In the latter city the number of deaths was reported as 1,649, as contrasted with 3,000 in 1918.