A party is thrown by Lisa Ludwig. She puts up a heated tent, hires a D.J. and invites people to eat, drink and dance the night away every year.

She has reduced the guest list over the years, but only once did she cancel completely. Something was bothering her when she sent out the invitations.

Ms Ludwig said that she had a knot in her stomach. Even before I see it on the news, I see the results in the lab where I work. People are tested for Covid, flu, or flu andRSV. I didn't like it all week.

The party was canceled a day before it was to be held. They called to say they couldn't come because of illness. The person was at the hair salon. It was necessary for another to stay healthy.

Ms. Ludwig said that everyone was happy.

Ms. Ludwig had a recent bout of Covid and still wasn't feeling 100%. At the height of the holiday party season, people are hungry for human interaction and a break from the swine flu. Companies are trying to get remote workers to come back to work.

According to Challenger, Gray & Christmas, nearly 60 percent of US companies plan to have work parties this year, up from 27 percent in 2021.

After a lean few years, caterers are thriving, according to a chef in New York who recently prepared a dinner for 40 guests. Most of her clients have stopped asking about the Covid protocols she has for her staff, but a few families with small children recently asked that the members of her crew take rapid tests.

Public health officials in New York and Los Angeles have warned of a surge in Covid and other respiratory illnesses. They stopped short of explicitly asking residents to change plans or stay home, instead suggesting that people wear masks in public indoor and outdoor environments.

Many hosts are requiring guests to take a rapid Covid test before entering the party.

The windows will be open on New Year's Day, but Dr. Dan Bauman wants people to test out the place before they come. He said that people go crazy about them.

His invitations asked his friends to join him in the holiday spirit.

Rapid testing is a good strategy for holiday partyers. Even if the tests are not perfect, they can still detect active infections.

While rapid Covid tests aren’t as sensitive as P.C.R. tests done in a lab, they may better predict how infectious a person is.Credit...Jim Wilson/The New York Times

When the viral load is low, rapid tests are less sensitive than tests that amplify the genetic material in a sample in a lab.

According to Bill Hanage, co-director of the Center for Communicable Disease Dynamics at Harvard T.H. Chan School of Public Health, a positive result on a rapid test may be related to how infectious you are.

When Dr. Hanage visits his parents in the UK for the first time in three years, he will be carrying a lot of test kits.

He said, "We cannot get the risk to zero, unfortunately, but we can reduce it considerably by vaccines, masks and, if people don't want to wear masks."

Reducing the guest list is a painful measure for many.

In November, José Xicohténcatl, a public relations professional in Huntington Beach, Calif., who goes byPepe, began planning a big company bash with a guest list of 100. In California, Covid cases began to climb.

The company decided to only allow employees to attend the party, with no clients or plus-ones. Guests have been asked to show proof of vaccinations or a negative test in the last 48 hours.

He wants employees to feel safe and comfortable.

He said that one of the things they had to do this year was make sure that they had some face time.

Mr. Xicohténcatl said that they can't party as much anymore.

Newsday pulled the plug on a newsroom party when Covid cases began to rise. There was a build-a-snowperson contest, a photo booth, and an appearance by the newspaper's mascot at the party.

Kim Grabina-Como said that the party was canceled because of the health and safety of their employees.

Some people are convinced that they were exposed at a holiday party.

Julie Bianucci, an IT project oversight manager for the state who has been working remotely, had to attend an office potluck because she is a manager. Her cookies were shaped like a Christmas tree.

Ms. Bianucci stayed for a while. There was no one wearing masks at the gathering. She was having trouble breathing after a few days of coughing.

She went to the emergency room. There was a positive test.

Ms. Bianucci canceled her Christmas plans, including a Christmas Eve dinner with her parents at her home, a trip to Napa Valley to see her sister, and another trip to visit her deceased husband's family.

On Christmas Day, she doesn't know if her children will open presents. They will all wear masks if that is the case.

No one can do all of the things that were planned. I did everything I could to not get it but I still got it. This is the worst it could possibly be.