County drive-through clinics are down to about 100 swabs each, Dr. Todd Flosi, chief medical officer of Ventura County Medical Center and Santa Paula Hospital, said on Monday, and the hospitals need to conserve the limited supply they have.

“If we run out of swabs for the hospital, it will clog our other processes up,” Dr. Flosi said, “because if someone is sick enough to be admitted but a test shows that they don’t have Covid-19, you can remove them from strict isolation guidelines faster, and that frees up space and protective gear.”

Ventura County Medical Center is in relatively good shape in terms of space to accommodate the expected influx of patients because it recently built a hospital building to meet strict state seismic building requirements meant to ensure that hospitals can withstand earthquakes. The old building can quickly be brought back to accommodate overflow, Dr. Flosi said, though administrators first need to figure out how to furnish it with actual beds. Cots and repurposed elective-surgery gurneys are among the options under consideration.

But the shortage of N-95 and surgical masks and other protective gear to treat the number of patients in need of hospitalization is so dire that Ventura hospital officials are looking to the community to supply handmade masks and equipment.

One nurse’s son is using his 3-D printer to make plastic face and eye shields for distribution. And a sewing circle that worked under the auspices of the nonprofit group that supports the county hospitals has shifted from helping to equip new mothers with necessities like burping cloths to sewing cloth masks from a pattern developed in consultation with the hospital’s medical personnel and guidelines from the Centers for Disease Control and Prevention.

Within 48 hours, the circle had grown to 150 sewers, who deliver the finished masks to a local trauma nurse in charge of quality control, said Amy Towner, the chief executive of the Health Care Foundation for Ventura County. She said sewers are innovating on the fly; after the hospitals’ laundry facilities said that elastic head bands would disintegrate with washing, they switched to a cloth tie-back pattern, and they are moving away from cotton to tea towel material after learning that would be more protective.

“A lot of our elderly population in particular want to help,” she said. “In World War II, women were making bullets to protect our country. Now they are at their sewing machines.”

Thomas Fuller reported from San Francisco and Tim Arango and Jo Becker from Los Angeles. Conor Dougherty contributed reporting from Oakland, Calif., and Jill Cowan from Los Angeles.