During a surge, 1,500 Sonoma County residents could be hospitalized with the coronavirus

More than 1,500 Sonoma County residents could require hospitalization for the coronavirus when infections peak in about two months, according to the first computer projections from an outside consultant that the county hired to determine the scope of local transmission of the infectious disease.

Without the county’s top public health official ordering people to largely stay home, COVID-19 illnesses would overwhelm local hospitals’ ability to treat stricken patients, requiring more than 10,000 hospital beds, according to modeling data county officials released Thursday.

“It’s very clear that shelter-in-place is working to flatten the curve,” of virus cases in the county of about 500,000 people, Dr. Sundari Mase, the county’s health officer, said during a news conference.

There are 95 confirmed local cases of the virus as of Thursday night among nearly 2,000 people tested for the disease, according to county data. That includes one death and 15 people who recovered. County officials announced on March 2 the first death of a local resident diagnosed with the coronavirus - a man in his 60s thought to have contracted it on a cruise - and they revealed on March 14 the first instance of a person infected through ?community transmission.

The first phase of the modeling, conducted by an epidemiologist at Imperial College London, shows the potential effects on the county of the new coronavirus with and without the county’s stay-at-home order, which started March 18 and runs through at least May 3. Mortality rates assumed that every one person infected would pass the virus to another 2½ people. The modeling shows that the order has likely reduced the number of county residents who are expected to die from COVID-19.

“One of the most critical things this model shows is that our shelter-in-place actions are working for our community,” Sonoma County Supervisor Lynda Hopkins said.

The unprecedented public health emergency directive likely will improve the mortality rate for those 65 and older from 0.8% to 0.28% of people infected; for those between ages 18 and 64, the mortality rate went from 0.18% to 0.1%.

With a virus reproduction rate of 2½ - each infected person potentially infecting 2½ other people - more than 10,000 residents would have required hospitalization had there been no shelter-in-place order.

The modeling also showed projections for a more dire scenario of three infections per each person who contracts the virus. Then the number of local people requiring hospitalization would be more than 5,000 even with the home isolation order in place. That crush of sick residents still would overwhelm the county’s expanded hospital capacity of about 1,500 beds, county officials said.

The models will help public health officials determine how and when to begin lifting isolation orders for Sonoma County residents that have ground public life to a near halt and shuttered businesses. Mase said that could start with easing restrictions for some businesses. Schools, she said, would be the last to resume.

A second wave of the virus will take place sometime after those isolation restrictions are lifted. But the timing and severity of a second peak will depend on the county’s ability to develop a robust slate of mitigation measures such as its efforts to track all those who have been exposed by people with COVID-19 to determine if they have symptoms.

“The ultimate mitigation measure would be a vaccine,” Mase said.

Without strong interventions, the county could see a resurgence of the coronavirus that would require 3,000 hospital beds at its peak.

Supervisor Shirlee Zane said the models were a sobering reminder that the most challenging days for the people of Sonoma County and its health care systems are yet to come.

“We haven’t even begun to see the crisis and we are doing the right thing and we need to keep doing it,” Zane said.

The report found that the stay-at-home order greatly minimizes the number of people 65 and older who will require a hospital bed. The number of beds older residents will require are significant only in a scenario with no shelter-in-place.

For example, had there been no such directive, those 65 and older would require some 1,000 hospital beds when infections peak two months from now, according to the report.

That’s if the virus caused 2.5 infections per case. If the per-person infection rate were 3 infections per case, older residents could require about 1,500 beds during the peak - which would also occur sooner.

Dr. George Rutherford, professor of epidemiology at UC San Francisco, said public health measures currently in place across the state and in many parts of the country are sure to have a dramatic effect on the spread of the virus.

Sonoma County is among those jurisdictions with the most effective public health intervention campaign ever during a respiratory virus outbreak well underway, he said.

“It’s one that’s well on its way to saving tens of thousands of lives in the Bay Area,” Rutherford said.

Rutherford said dire projections, such as the ones that were released globally several weeks ago, may not be very useful from a public health standpoint. Rutherford is working on modeling for the Bay Area, in conjunction with state health officials, that examine the impact of shelter-in-place orders.

“We’re acting as if it may be worse in terms of preparedness but we understand that it may well be better,” he said.