Transmissibility and geographic spread of the 1889 influenza pandemic

Abstract

Until now, mortality and spreading mechanisms of influenza pandemics have been studied only for the 1918, 1957, and 1968 pandemics; none have concerned the 19th century. Herein, we examined the 1889 "Russian" pandemic. Clinical attack rates were retrieved for 408 geographic entities in 14 European countries and in the United States. Case fatality ratios were estimated from datasets in the French, British and German armies, and morbidity and mortality records of Swiss cities. Weekly all-cause mortality was analyzed in 96 European and American cities. The pandemic spread rapidly, taking only 4 months to circumnavigate the planet, peaking in the United States 70 days after the original peak in St. Petersburg. The median and interquartile range of clinical attack rates was 60% (45-70%). The case fatality ratios ranged from 0.1% to 0.28%, which is comparable to those of 1957 and 1968, and 10-fold lower than in 1918. The median basic reproduction number (R(0)) was 2.1, which is comparable to the values found for the other pandemics, despite the different viruses and contact networks. R(0) values varied widely from one city to another, and only a small minority of those values was within the range in which modelers' mitigation scenarios predicted effectiveness. The 1889 and 1918 R(0) correlated for the subset of cities for which both values were available. Social and geographic factors probably shape the local R(0) , and they could be identified to design optimal mitigation scenarios tailored to each city.

Fig. 1.

Spread of the 1889 pandemic throughout continental Europe (2006 boundaries) during six successive periods. Each panel refers to a period of one or several weeks shown on the calendar in the Inset. Red dots indicate the places of the mortality peaks that occurred during this period and are proportional to peak size. Green dots indicate cities after the mortality peak has passed. The whole set of European cities studied can be visualized in the last panel (68 in continental Europe and 14 in the United Kingdom and Ireland). Movie S1 shows the week-by-week spread in Europe and in the United States.

Fig. 2.

Distributions of 1889 pandemic mortality peaks and R₀ values. (A) Peak sizes for 96 cities worldwide. The peak size for each city is the relative mortality increase at the peak's highest amplitude compared with baseline mortality; e.g., a peak size of 3 indicates that the excess mortality at the peak was three times the baseline mortality. (B) Estimates of R₀ values, assuming CFR = 0.2%, and respective Weibull distributed latent and infectious periods with means of 1.6 and 1.0 days.

Fig. 3.

(A) Spearman rank correlations between R₀ estimations, population size, peak sizes, peak times (for all cities), and latitudes (for European cities). Significance levels: P < 10⁻⁵ for |r| > 0.45; P < 10⁻⁴ for |r| > 0.40; P < 10⁻³ for |r| > 0.35, P < 0.05 for |r| > 0.20. (B) Correlation between 1918 (12) and 1889 R₀ values (this study) for the 11 US cities studied in common (Ba, Baltimore; Bo, Boston, Ci, Cincinnati; Cl, Cleveland; De, Detroit; In, Indianapolis; Mi, Minneapolis; NY, New York; Pr, Providence; SF, San Francisco; Wa, Washington). Pearson's correlation = 0.62 (P < 0.05). Dotted line corresponds to linear regression.

Fig. 4.

Fit of influenza mortality rates obtained with the SEIR model for the 10 cities with the largest population sizes. Thin lines indicate raw data; bold lines indicate model fits.