Los Angeles – In normal times, the Super Bowl is one of the country's premier social occasions — bringing enthusiasts and nonfans alike together for hours of football-fueled festivities.

But in the era of COVID-19, officials and experts say Sunday's game poses a tremendous risk, and that widespread large watch parties could imperil California's precarious emergence from the pandemic's worst wave.

"Don't fumble this. We're almost there," said Dr. Mark Ghaly, California's health and human services secretary. "Let's keep our guard up a little bit longer."

The warning against Super Bowl parties is as much about avoiding the mistakes of the past as it is staving off future calamity. A big warning sign is the rise of the more contagious and possibly deadlier strain of the coronavirus first identified in Britain, B.1.1.7, that has seen considerable growth in San Diego County, which has already likely resulted in one death there and represents nearly one-quarter of the known cases nationwide.

The U.K. variant is believed to be 50 to 70% more transmissible than the regular variety of the circulating virus. Simulations presented by a UC San Diego scientist to government officials warned that even with a decent vaccination strategy, average new daily coronavirus cases in San Diego County within two months could be twice as bad as the peak during the autumn and winter surge, overwhelming hospital capacity there, if residents again reject public health guidance to wear masks and avoid gatherings as they did late last year.

"If we let down our guard and end up having large numbers of people in our home, inside, not masked, yelling for our teams, then we can see a potential reversal of the downward trend and end up with a new surge," said Dr. Robert Kim-Farley, medical epidemiologist and infectious diseases expert at the UCLA Fielding School of Public Health.

California's autumn and winter surge has faded in part because more people followed the stay-at-home rules.

"However, the Super Bowl could be an opportunity for that mixing again to occur," Kim-Farley said. "And that's why we need to make sure we're getting a message out: This Super Bowl is not the time to have a large party. Wait until next year."