From the Zika virus to a safety recall that rendered hundreds of units of blood useless, several factors have caused Southern California’s blood supply to dip to dangerous lows, local health officials said Tuesday.

The blood supply is getting so low that the American Red Cross, for the first time in eight years, has issued an emergency call for blood and platelets – cells in the blood – urging all eligible donors to give now to replenish the reserves.

The shortage is not exclusive to Southern California. Across the country, blood banks have seen 39,000 fewer donations over the past few months coupled with a spike in the demand for blood since early this year, said Dr. Ross Herron, chief medical officer of the Red Cross West Blood Services Division.

He said the Red Cross strives to keep a five-day supply available at all times to meet the needs of patients every day and to be prepared for emergencies.

But in Southern California, the Red Cross has less than a five-day supply on hand, he said. On some days over the past few months, the region’s blood supply has dipped to a two-day level, Herron said.

“Right now, blood products are being distributed at a faster level than they are coming in,” he said. “That’s why we’ve issued an emergency call.”

Summer is typically slow for blood donations because nearly 25 percent of the supply comes from school and college campus blood drives, Herron said.

Also, new regulations from the Food and Drug Administration on men’s iron levels and the Zika virus have further affected blood supply, he said.

Travelers to Zika-infected regions – including areas of Central and South America, the Caribbean and the Pacific Islands – must wait 28 days before they can donate blood. And in May, the FDA raised the minimum hemoglobin count – an indication of iron level – for male donors from 12.5 grams per liter to 13 grams per liter, further reducing the number of donations.

At Orange County Global Medical Center, which in Santa Ana houses the largest trauma center in the county, blood supplies are on par with their preferred levels, which is about a week’s worth of blood supply when the demand is normal, said laboratory director Michelle Bosewicht.

But the center came close to going below that figure last month, she said, when its blood supplier, San Bernardino-based Lifestream, recalled 2,000 units of blood because of an issue with collection bags and filters.

“The current blood shortage is real and it’s nationwide,” Bosewicht said. “So far, we’ve been able to keep levels. But we want to be certain that our facilities can handle traumas and emergencies in the community as well. And for that, we’re going to need the public’s help with blood donations.”

Contact the writer: 714-796-7909 or dbharath@ocregister.com