WASHINGTON, Dec 29 (Reuters) - A new wave of COVID-19 infections driven by the Omicron variant is forcing the U.S. National Institutes of Health to postpone elective surgeries at the largest hospital in the United States devoted to clinical research as a growing number of staff must isolate or quarantine, according to a memo reviewed by Reuters. Dr. James Gilman, the chief executive officer of NIH"s clinical center, said in an email to staff on Wednesday that beginning next week, elective surgeries would be delayed. At least 80 clinical center staff called in sick on Wednesday alone because of COVID-19 infections or exposures. NIH also is "running dangerously low" on the chemicals required by its laboratories to test for COVID-19 and "reagents are in short supply everywhere," Gilman wrote. The decision is indicative of the kinds of workforce disruptions that are expected as Americans return to their jobs next week following the winter holidays. Across all of NIH, 250 new cases of COVID-19 have been reported between Dec. 20-27 out of an estimated 40,000 staff. "The situation has gotten a little bit worse each day," Gilman wrote. "If there is any good news, it may be that the Omicron peak should be rapid and we can get back to business as usual soon. However, we cannot do business as usual next week." The silver lining is that many cases among staff are mildly symptomatic and don"t appear to be spreading within the workplace, Gilman said. "The Clinical Center doesn’t currently have staff shortages," NIH spokesperson Renate Myles said. "Dr. Gilman is proactively making changes in anticipation of potential shortages." Last week, the U.S. Centers for Disease Control and Prevention reduced the isolation period required of healthcare workers, fearing the highly-transmissible Omicron would sideline critical staff just as hospitals are flooded with new COVID patients. The CDC this week also cut in half the recommended isolation period for other Americans with asymptomatic COVID in advance of an expected surge that could force workers in many other industries to stay home even if they aren’t ill or infectious. "I point out again the inadvisability of having patients travel to our area (an Omicron hotspot) for any eventuality other than a dire emergency," Gilman wrote to NIH clinical center staff in the suburb of Bethesda, Maryland, outside Washington. They help run hundreds of clinical trials, including for cancer research and rare diseases. "I apologize in advance for taking this precipitous action without more advanced warning but extreme circumstances again call for extreme measures," Gilman wrote.