Anyone here have flu?

California, week of Oct 18–24 (latest CDC data). Make a guess first.


20%

About 0.4% of Californians are contagious with flu on a given day in the week of Oct 18–24 (range 0.3%–0.7%), or about 1 in 269. That is already higher than the worst week of 2016-17, 2018-19, 2021-22.

Red/grey: the same week of each season. Light bar: that season's worst week.

2016-170.01%
2017-180.02%
2018-190.01%
2019-200.02%
2020-210.00%
2021-220.00%
2022-230.08%
2023-240.03%
2024-250.02%
2025-260.01%
2026-270.4%

How this is worked out. Each week CDC reports what share of California doctor visits are for flu-like illness and what share of flu tests come back positive. Their product tracks flu infections, up to a scale factor. That factor comes from matching each past season to CDC's estimate of how many Americans got sick with flu that season (six seasons; it varies 2.6x, so the range uses the lowest and highest). Someone is counted as contagious for 5 days. The odds for a room then assume its people are a random draw from California: a dorm or a class where flu is already going round will be higher than this, and a room of people staying home when sick will be lower. Data: CDC FluView via Delphi Epidata; US illness totals from CDC's flu burden estimates. Built 2026-11-04.