Let your lazy fingers do the walking.https://www.cnn.com/2020/03/15/us/philadelphia-1918-spanish-flu-trnd/index.html?utm_source=fark&utm_medium=website&utm_content=link&ICID=ref_fark
That article provides little of the data the other poster was seeking.
It is the job to the one making the assertion to substantiate it (and as you could tell from my many postings, i provide much of that), and while you now have a source for the report, yet it does not provide much re. the factors needed to support your premise.
Except it somewhat does as regards population make up, as it reports,
The virus spread to Philadelphia on September 19, 1918, through the Philadelphia Navy Yard, In a matter of days, 600 sailors had the virus....the parade went on as scheduled on September 28, bringing 200,000 Philadelphians together.
Other factors contributed to the flu's spread, including high population and poor working and living conditions.
St. Louis, for example, canceled its parade while Philadelphia did not. In the end, the death toll in St. Louis did not rise above 700, according to the CDC - https://www.cnn.com/2020/03/15/us/philadelphia-1918-spanish-flu-trnd/index.html?utm_source=fark&utm_medium=website&utm_content=link&ICID=ref_fark
And as for pop. size, in 1920: Philadelphia 1,823,779 vs. 687,000 for city of St. Louis, Missouri in 66 sq mi .
And there is more to be considered in this dissimilar comparison.