What should you do if you or someone with whom you have been in close contact tests positive for coronavirus during the holidays?

As families and friends gather to celebrate Christmas, New Years and other holidays, many are looking for information on how long to quarantine, if at all and how long they might be contagious.

Here's a look at the guidance from the Centers for Disease Control and Prevention on what to do if you test positive or believe you were exposed to someone who has.

According to the CDC, COVID symptoms can appear anywhere from two to 14 days after someone is exposed to the virus.

Anyone with symptoms should get tested for COVID.

Those who have been fully vaccinated and around someone who has COVID-19 are recommended to get tested between five and seven days after their exposure, according to the most recent guidance from the CDC, though previous guidance had been between three and five days.

Those who develop symptoms should get tested as symptoms develop, but if a test is negative and symptoms persist another test might be needed a few days later, particularly for those who use at-home test kits.

"So if someone is having symptoms and they get a negative test, one, it depends on the severity right? If you're having severe symptoms we don't want you to just do a home test either," said Dr. Nimmi Rajagopal, the associate chair of the Department of Family and Community Medicine for Cook County Health. "We want you to call your doctor's office and make sure that they have an opinion here because there are of course other things like the flu that are out there that can mimic symptoms or have similar symptoms. But if you're having symptoms and they're kind of mild and lingering and you use the [at-home] test and it's negative, we want you to take the precautions and then retest in three to five days. And that's why most of these kits actually come with two tests."

A person with COVID-19 is considered infectious starting two days before they develop symptoms, or two days before the date of their positive test if they do not have symptoms.

First things first, those who believe they have been in contact with someone who has COVID and are unvaccinated should quarantine. Those who test positive, regardless of vaccination status, must isolate, according to the Centers for Disease Control and Prevention.

Those who have been within 6 feet of someone with COVID for a cumulative total of at least 15 minutes over a 24-hour period should stay home for 14 days after their last contact with that person and watch for symptoms. If possible, those quarantining should also stay away from the people they live with, particularly those who are at an increased risk of developing more severe COVID illness.

If symptoms appear within the quarantine window, isolate immediately and contact a healthcare provider, the CDC's guidance states.

Those who are fully vaccinated do not need to quarantine, according to the CDC, but they should get tested anywhere from five to seven days following their exposure regardless of symptoms.

Local health authorities can also make the final determination about how long a quarantine should last, however. And testing can play a role.

For example, in Chicago, those who travel to or from certain parts of the country and are unvaccinated must quarantine upon arrival to Chicago, but the length of time they should do so for depends on whether they get tested for COVID.

The city's travel advisory recommends those who travel from the designated warning states must:

Illinois' health department states that:

"Due to the risk of severe illness and congregate transmission, IDPH recommends the full 14-day quarantine period rather than the shortened options described above in congregate living settings with vulnerable populations, such as skilled care and correctional facilities," the Illinois Department of Public Health states on its website.

For schools, the guidance is different. In these settings, IDPH guidance states that:

According to the CDC, people who are positive for COVID should stay home until it's safe for them to be around others, including even other members of their home.

Health officials recommend a "sick room" or area for those who are infected and a separate bathroom, if possible.

So how do you calculate your 10-day isolation period?

According to the CDC, "day 0 is your first day of symptoms." That means that Day 1 is the first full day after your symptoms developed.

For those who test positive for COVID but have no symptoms, day 0 is the day of the positive test. Those who develop symptoms after testing positive must start their calculations over, however, with day 0 then becoming the first day of symptoms.

The CDC urges those who have or may have COVID-19 to watch for emergency warning signs and seek medical care immediately if they experience symptoms including:

"This list is not all possible symptoms," the CDC states. "Please call your medical provider for any other symptoms that are severe or concerning to you."

You can also notify the operator that you believe you or someone you are caring for has COVID.

Those who test positive using an at-home test are asked to follow the latest CDC guidelines and communicate the results to their healthcare provider, who is responsible for reporting test results to the state health department.

Chicago Department of Public Health Commissioner Dr. Allison Arwady has said that that process is not likely happening for every test, however.

"All of those negatives realistically are not being reported," Arwady said. "We're not counting, you know, it's a fiction that we've ever counted every COVID test."

She added that though many home tests are not being reported, positive results likely are provided to health care providers, then to the health departments.

If you had symptoms, the CDC says you can be around others if you meet the following criteria:

The CDC says these recommendations don't apply to those who have severe COVID or weakened immune systems, however.

If you tested positive but had no symptoms for the duration of your isolation, the CDC says:

For those with severe illnesses or weakened immune systems, the CDC says staying home up to 20 days after symptoms first appeared is advised, but people in this group should talk to their healthcare provider before making decisions.

"People with weakened immune systems may require testing to determine when they can be around others," the CDC's website states. "Talk to your healthcare provider for more information."