With the winter cold and flu season upon us, Americans should be on the lookout for another ultra-contagious virus: our most common stomach bug.

The U.S. experienced the largest December norovirus surge since at least 2012, according to data from the Centers for Disease Control and Prevention.

During the week of Dec. 5, state health departments recorded 91 separate outbreaks nationwide, according to the CDC. The next highest figure for that week since 2012 was 65 outbreaks.

Through November, there have been 55 laboratory-confirmed cases of norovirus in California, according to the state department of public health. Data from December are not yet available.

Outbreaks are typically more widespread in January and February, the data show, raising concerns that the spike could continue.

Most norovirus cases are transmitted directly from one person to another, the CDC said, from actions such as touching food or eating utensils. Restaurants, cruise ships, healthcare facilities and schools are common transmission sites.

Additionally, contaminated food, water and surfaces can spread the virus.

Last week, the U.S. Food and Drug Administration issued advisories warning businesses and consumers against serving or eating oysters from Washington state, Canada and Korea which may be contaminated with norovirus.

Annually, the CDC reports some 2,500 outbreaks nationally. But real-time monitoring data only cover 14 states: Alabama, Colorado, Massachusetts, Michigan, Minnesota, Nebraska, New Mexico, North Carolina, Ohio, Oregon, South Carolina, Tennessee, Virginia and Wisconsin.

Around half of outbreaks of food-related illness are caused by norovirus, per the CDC.

The most common symptoms of norovirus are vomiting, diarrhea, nausea and stomach pain. Symptoms usually improve in one to three days, but those infected can still spread the virus for several days after symptoms ease.

The best ways to prevent the virus from spreading: washing hands, cooking shellfish thoroughly, washing fruits and vegetables, cleaning and disinfecting contaminated surfaces, washing laundry in hot water and staying home for two days after symptoms stop.

The main treatment for norovirus is hydration to replace fluids lost by the patient. Those with severe dehydration should seek medical attention, the CDC advises.

The ads on podcasts and social media were tantalizing: over-the-counter probiotic supplements that could ward off the worst effects of a hangover if taken before drinking.

As a bourbon reviewer who enjoys the flavor of spirits but has always been easily prone to hangovers, Eric Burke was intrigued. He ordered a few bottles of Pre-Alcohol, a probiotic drink from the company ZBiotics, to test it out.

He downed the mixture of water, salt, flavoring and genetically modified bacteria. He followed it with a cocktail, a meal and two bourbons, and woke the next morning feeling considerably more chipper than he’d have expected.

The next night, emboldened by success, he drank another half-ounce bottle of Pre-Alcohol. He drank a bit more than the previous night — a beer with dinner and then four tumblers of bourbon.

That amount that typically would leave him feeling achy and sluggish the day after.

Which was exactly how he felt when he opened his eyes hours later.

“That one was unpleasant,” said Burke, 48. “I woke up that morning being just like, ‘Well, I’m not 21 anymore.’ ”

A hangover is a collection of physical and mental symptoms resulting from the inflammation and oxidative stress that alcohol wreaks in the human body.

One of many factors contributing to day-after misery is the accumulation of acetaldehyde, a chemical byproduct of the beverages’ ethanol breaking down in the body. Acetaldehyde is a carcinogen that features prominently in the nausea, stomach upset, sweats and other physical symptoms associated with over-consumption.

ZBiotic’s Pre-Alcohol and the Swedish biotech company De Faire Medical AB’s competitor supplement Myrkl both rely on live bacteria to process excess acetaldehyde. Other researchers and recreational drinkers have also experimented with probiotics for similar ends.

Reducing the amount of acetaldehyde, the hypothesis goes, should also reduce the physical symptoms caused by its buildup.

“The more you drink, the more you’ll have to deal with the effects of other things besides acetaldehyde,” ZBiotics CEO Zack Abbott said via email when asked about Burke’s results. “That being said, for the vast majority of people, acetaldehyde is a major factor, and Pre-Alcohol therefore results in them feeling better (if not perfect) the next day.”

The U.S. Food and Drug Administration considers ZBiotics and Myrkl to be dietary supplements or functional foods, not drugs, and thus doesn’t evaluate their health claims. Microbiome experts caution that a probiotic supplement alone won’t spare you from the worst effects of overindulgence.

For starters, the bloodstream carries most of the ethanol in an alcoholic beverage straight to the liver, where an enzyme called alcohol dehydrogenase breaks it down into acetaldehyde. The brain, gastrointestinal tract and pancreas process some alcohol as well. Only a relatively small amount of ethanol is metabolized in the intestines, where probiotics do their work.

Adding probiotics to your pre-party regimen won’t cause you any harm, said Karsten Zengler, a microbiologist and professor of pediatrics and bioengineering at UC San Diego.

But it’s also unlikely to have a substantial effect on how you feel the next day, as your intestines come pre-equipped with an army of bacteria capable of breaking down alcohol’s byproducts, he said.

“There is not a lot of ethanol and acetaldehyde in your large intestine to start with,” Zengler said, and “the vast majority of the bacteria in your gut already metabolize acetaldehyde for you, so just adding something more might not do the trick.”

ZBiotics has funded studies demonstrating both the safety of their product and that their bacteria effectively broke down a significant amount of acetaldehyde in simulated gut conditions in a lab. As for the real-world effects of that breakdown, Abbott pointed to an outside 2006 paper that found that rats given ethanol had fewer hangover-like symptoms the next day when acetaldehyde was removed.

Myrkl funded a small study that showed its product lowered blood-alcohol levels in some participants. Subjects were instructed to take the supplement for a week prior to drinking, rather than the single pre-party dose instructed on the packet.

The hard truth, said Joris C. Verster, a pharmacology professor at Utrecht University in the Netherlands and founder of the Alcohol Hangover Research Group consortium, is that there is currently one scientifically validated way to prevent hangovers: drink less alcohol.

“Although there are many hangover products marketed, there is no convincing scientific evidence that these treatments are effective. Independent double-blind, placebo-controlled clinical trials in social drinkers are needed,” Verster said. “Currently, the only effective way to prevent a hangover is to consume alcohol in moderation.”

Unpleasant as they are, hangovers serve a valuable purpose, said Dr. Daryl Davies, a clinical pharmacy professor and director of the Alcohol and Brain Research Laboratory at USC Mann School of Pharmacy and Pharmaceutical Sciences.

“What I tend to tell people is if you are getting hangovers, you are drinking too much,” Davies said. “It is the body trying to tell you that something is wrong.”

A former Van Nuys physician who recently surrendered his medical license following sexual harassment accusations has agreed to a $15-million federal settlement over allegations that he and fellow defendants submitted false claims to Medicare and Medi-Cal.

The U.S. Department of Justice accused Mohammad Rasekhi, his spouse and business partner, Sheila Busheri, the medical center he founded and a laboratory he co-owned of engaging in a number of schemes to defraud Medicare and Medicaid from 2014-22, the U.S. attorney’s office said this week.

Rasekhi was the founder and chief medical officer of Southern California Medical Center, a group of general practice clinics with locations in El Monte, Van Nuys, Pico Rivera, Woodland Hills, Pomona and Long Beach. He and Busheri also co-owned Universal Diagnostic Laboratories, a medical test facility based in Van Nuys.

Busheri, who is chief executive of SCMC, said the pair deny all allegations. However, “due to the high cost of litigation and issuance of a crippling payment suspension, fighting the allegations to prove the absence of wrongdoing meant closing SCMC’s doors, effectively denying care to thousands of underserved patients,” she said in a written statement. “With that in mind, a business decision was made to resolve the matter.”

An attorney who represented Rasekhi in the surrender of his medical license didn’t immediately return requests for comment.

According to the settlement agreement, Rasekhi, Busheri and their businesses allegedly paid marketers illegal kickbacks to refer Medicare and Medi-Cal patients to SCMC’s clinics. They gave outside medical clinics illegal perks and payments so that they would refer federally supported patients to UDL for lab tests, the agreement said, and referred SCMC patients who received Medicare and Medi-Cal benefits to UDL for testing, in violation of federal laws against self-referrals.

“Kickback and self-referral schemes risk impairing the judgment of healthcare providers and diminish the reliability of the care that they render,” Brian M. Boynton, head of the Justice Department’s Civil Division, said in a statement. “Medicare and Medicaid beneficiaries deserve care that is free from the taint of referrals that were driven by the providers’ financial interest.”

Under the terms of the settlement, the defendants will pay $10 million to the government and $5 million to a group of former SCMC and UDL staff who filed a whistleblower suit against their former employers.

California will be reimbursed $7 million for Medi-Cal claims related to the suit, the U.S. attorney’s office said.

Rasekhi surrendered his medical license earlier this month, weeks after the Medical Board of California filed an accusation against him detailing allegations that he sexually abused three women under his care.

His attorney said Rasekhi denied all the allegations, and chose to waive his rights to a hearing and retire from medicine rather than contest the accusations.