Tuesday was the first day of winter. And as cold temperatures keep more people indoors and the holidays bring people together, germs will spread.

"We know that the winter weather itself makes us more susceptible to infection. It has to do with the drier air and the ability for respiratory particles to actually stay suspended in the air for a longer period of time,” says Deena Gupta-Adimoolam, a specialist in primary care prevention and endocrinology.

As people travel around the holidays, some experts say that they predict that roads and airports will be at almost pre-pandemic levels.

“If you aren’t vaccinated, I would still highly recommend getting vaccinated and boosted before making any significant travel plans. It’s obviously very important to also continue wearing a mask on all public transportation,” Gupta-Adimoolam says.

Experts say that it is important for anyone traveling to familiarize themselves with local hospitals in case they get sick. When considering gathering with friends and family, one should not go if they feel ill, regardless of vaccination status. If gathering with someone who is at risk, it is a good idea to get tested before seeing them. Doctors also say that everyone should be following common-sense practices.

"Maintain social distancing greater than six feet. If you cannot do so, then it is advised to put on a mask. Frequent hand washing is also recommended,” says Dr. Alexander Sarenac, medical director of emergency medicine at Hudson Regional.

But experts say that they believe that there will be an increase in virus transmission over the next few weeks.

"There's going to be an increase in the virus being spread. Some of those people will be breakthrough cases. Some of them will get sick, so we fully expect to see an increase after the holidays,” says Sarenac.

The exact increase is unclear, but after Thanksgiving, cases jumped by over 20% nationwide in the weeks following the holiday.

The Centers for Disease Control and Prevention says that the flu season peaks between December and February. COVID cases nationwide peaked in December 2020 and January 2021 and are on the rise again, with record-high daily new COVID cases in some places.