Officials in St. Louis introduced a broad series of public health measures to contain the flu within two days of the first reported cases. Philadelphia, New Orleans and Boston all used similar interventions, but they took longer to implement them, and as a result, peak mortality rates were higher. In the most extreme disparity, the peak mortality rate in St. Louis was only one-eighth that of Philadelphia, the worst-hit city in the survey. In contrast to St. Louis, Philadelphia imposed bans on public gatherings more than two weeks after the first infections were reported. City officials even allowed a city-wide parade to take place prior to imposing their bans.
If St. Louis had waited another week or two, they might have fared the same as Philadelphia, says the lead author on the first study, Richard Hatchett, M.D., an associate director for emergency preparedness at NIAID. Despite the fact that these cities had dramatically different outcomes early on, all the cities in the survey ultimately experienced significant epidemics because, in the absence of an effective vaccine, the virus continued to spread or recurred as cities relaxed their restrictions.
The second study also shows that the timing of when control measures were lifted played a major part. Cities that relaxed their restrictions after the peak of the pandemic passed often saw the re-emergence of infection and had to reintroduce restrictions, says Neil Ferguson, D.Phil., of Imperial College, London, the senior author on the second study. In their paper, Dr. Ferguson and his coauthor used mathematical models to reproduce the pattern of the 1918 pandemic in different cities. This allowed them
Source:NIH/National Institute of Allergy and Infectious Diseases