*Weekly hospitalizations are estimated because the mandate for US hospitals to report flu hospitalizations recently expired, causing the percent of hospitals reporting to drop from nearly 100% to well below 50%. To make data from recent months comparable to data from when reporting was stil mandatory, I applied the following simple formula:

Estimated hospitalizations = reported hospitalizations / proportion of hospitals reporting

While there is uncertainty due to the low reporting rate, this simple method accounts for reduced reporting and is corroborated by emergency department data from CDC NSSP.