Making sense of the Bay Area coronavirus hospitalization data

Bay Area hospitalization data from April 1, 2020 to April 9, 2020. Bay Area hospitalization data from April 1, 2020 to April 9, 2020. Photo: Blair Heagerty/SFGATE Photo: Blair Heagerty/SFGATE Image 1 of / 45 Caption Close Making sense of the Bay Area coronavirus hospitalization data 1 / 45 Back to Gallery

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When it comes to trying to pinpoint where we are on the "curve" of the coronavirus pandemic at any given moment, experts agree that hospitalization numbers are a much better metric to use than raw number of cases.

"Cases are a function of testing," UCSF epidemiologist Dr. George Rutherford told SFGATE. "Hospitalizations are hard numbers."

The State of California began providing data on the number of patients requiring hospitalization and intensive care at the county level at the beginning of April, which means it's now possible to track Bay Area hospitalizations over time. The bulk of the hospitalizations are being reported in Santa Clara, San Francisco, Alameda, San Mateo and Contra Costa counties, with none showing trends dramatically out of line with the others.

The state reports both the number of patients confirmed to have COVID-19 as well as "suspected COVID-19" cases, which the state defines as hospitalized patients presenting typical coronavirus symptoms awaiting test results.

On April 1 — the first day the state reported data for the nine counties that make up the Bay Area – there were 758 patients hospitalized and 241 in intensive care units. Those numbers then rose for two additional days before steadily dropping for the next three days.

Then on April 7, the number of hospitalizations jumped from 759 to 831, a 9.5 percent increase from the previous day, and the number of ICU patients rose from 276 to 283, a 2.5 percent increase. Both metrics then posted back-to-back decreases on April 8 and 9.

Photo: Blair Heagerty/SFGATE Bay Area hospital intensive care unit data from April 1, 2020 to...

What, if anything, can we infer from this data?

Rutherford is encouraged that the Bay Area has not recorded a double-digit percent increase thus far, calling the April 7 data point to a "potential peak" while cautioning not to take that to the bank — yet.

“I think it’s flat," he said. “You don’t know what’s gong to happen next week, as this thing could still go up. But as of now, this is flat, flat, flat, flat. You expect some fluctuation but the overall trend is flat.”

As for where we are on the curve? Rutherford believes it's possible the Bay Area could perhaps be at or nearing its "peak," since the region started sheltering in place before the rest of the state and country. He also stressed it's worth being mindful of the regional differences whenever state officials cite statewide hospitalization figures, or when models project statewide peaks.

“Los Angeles cases are way higher, like ten-fold higher than San Francisco, and Southern California is eight-fold higher than Northern California,” he said. “It went up very rapidly in Southern California largely driven by L.A. a week after statewide shelter in place, but this was a rapid rise that was not seen in the Bay Area since we went into shelter in place three days earlier.”

However, the statewide hospitalization figures have also been relatively flat in recent days, with Governor Gavin Newsom expressing guarded optimism after the number of individuals in intensive care units decreased Thursday.

"One data point is not a headline, so I caution anybody to read too much into that one point of data,” he said. “But nonetheless, it is encouraging. It reinforces the incredible work all of you are doing."

There are only nine days worth of data to this point, and with the influential IHME model projecting the state's hospitals will reach "peak resource use" at the beginning of next week, it will be worth keeping an eye on these numbers over the next few days.

You can view the Bay Area's hospitalization and ICU data in the graphs above, and click here to see the state's records for each county's data by day.

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Eric Ting is an SFGATE digital reporter. Email: eric.ting@sfgate.com | Twitter:@_ericting