Never has so much of life depended on the pitch of a single curve.
In New York, the curve is so steep it has looked like the side of a building. In the Lombardy region of Italy, a steep Alpine ski slope. In San Diego – which is days behind both places – the curve is an emerging mountain, height unknown.
But the data of the last week has been “encouraging,” said Dr. Mark Sawyer, an infectious disease specialist at Rady Children’s Hospital. The rate of new cases during the last seven reported days has slowed significantly from the week prior, according to a Voice of San Diego analysis.
Public health officials say that aggressive social distancing measures appear to be working but caution that more data is needed to truly understand the trajectory of San Diego’s outbreak.
“The data suggests we may be getting a handle on things,” said Sawyer. But he emphasized that social distancing measures would need to stay in place for weeks. “I’m pretty sure it would all come roaring back and be worse, and we would see an exponential rise,” if we ended social distancing now, he said.
Massively increasing San Diego’s testing capacity will be the only way to begin to emerge from social distancing, Sawyer said. Officials need to be able to test those with no symptoms or mild symptoms to deem whether they are ready to come out of isolation. San Diego currently has only enough tests for those with severe symptoms or those who are medically fragile.
So much depends on how quickly new cases double.
Local models have shown that if the number of COVID-19 cases doubles every three days, San Diego’s hospitals would be quickly overrun. Hospital beds and ventilators would be maxed out. Doctors and hospitals would have to make unthinkable decisions.
If cases double every six days, the pitch of the curve would be lower, but hospitals could still be crushed by the surge of patients.
Data from the last week suggests San Diego’s current doubling rate is anywhere between eight and 11 days, depending on how it’s calculated. That is a slower doubling rate than previous weeks – but a doubling rate of eight days could still put the health care system in serious jeopardy.
The week prior, the number of new cases appeared to be doubling every four to five days – an extremely alarming figure.
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Coming up with a solid estimate of the growth rate is difficult because the number of new cases each day is erratic. This is compounded by a general lack of testing, as well as the varying number of tests completed each day. In the last 14 reported days, the number of completed tests each day has swung wildly between 687 and 2,606.
When the number of tests plummets downward on certain days, the official number of new cases becomes less reliable.
San Diego officially has roughly 7,000 hospital beds. (New temporary structures and military beds would also be able to handle some patients, but county officials have not released numbers on official surge capacity.) As of Wednesday, there were 533 ventilators available to be used.
The six-day model created by county public health officials suggested that San Diego could have 7,000 coronavirus-related hospitalizations by May 10. To handle such a surge, hospitals would need to be completely empty of other patients. Obviously, they are not. Patients still must come in to have appendixes removed and broken arms mended.
Hospitals have historically been occupied at a roughly 50 percent rate. In other words, on any given day, 3,500 beds are typically in use. The six-day model suggests San Diego would reach 3,500 coronavirus hospitalizations by May 6.
County Supervisor Nathan Fletcher has said that hospitals are currently under their historic occupancy rate. But he declined to provide specific figures on exactly how many people are currently in San Diego hospitals. The cancellation of elective surgeries in particular has reduced hospital occupancy.
Among COVID-19 patients, Fletcher said hospitalizations are doubling every seven days. Depending on how the figure was calculated, it could provide a more stable window into San Diego’s doubling rate, since hospitalizations are not affected by the rise and fall of testing capacity on a daily basis.
Depending on current hospital occupancy, a seven-day doubling rate could still be disastrous.
Dr. Nick Yphantides, the county’s chief medical officer, agreed the numbers over the last week have been encouraging.
“We embrace this as an encouraging sign,” he said. “It is too early and not to be taken in any way as an interpretation that we should get ready to go out and do our thing.”
He emphasized more data needs to become available to understand the long-term doubling rate of COVID-19 cases.
Both Yphantides and Fletcher also said that coming out of social distancing measures too soon could cause the peak to start sharply rising, even faster than before.
The only way to speed up any gradual easing of social distancing measures would be for San Diego to have an abundance of tests, Sawyer said. Testing symptomatic and non-symptomatic individuals is the only way to determine for sure whether it is safe for someone to come out of isolation. Sawyer said it would likely be weeks before San Diego has the testing capacity necessary to clearly understand when it is safe to start easing social distancing restrictions.