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The US Centers for Disease Control and Prevention put out its new Covid-19 guidelines for camps on Friday.

Over 3.94 million children have tested positive for Covid-19 since the start of the pandemic, according to the American Academy of Pediatrics, yet severe illness seems relatively rare among children. Still, the CDC says kids can get sick and spread it to others, so it is good to take precautions and its important to get vaccinated. For those who are fully vaccinated, these guidelines show some real advantages.

The CDC said staff and campers who are fully vaccinated don’t need to wear masks, except where required by federal, state, local, tribal, territorial regulations or if it is a business or workplace policy.

“Although fully vaccinated persons do not need to wear masks, camps can be supportive of staff or campers who choose to continue to wear a mask,” the new guidelines said.

The CDC also encouraged everyone 12 years and older to get vaccinated for Covid-19, underscoring that vaccines are safe and effective. It also encouraged camps to develop education materials and promote vaccination among campers and staff.

The agency said people who are fully vaccinated do not need to undergo routine testing, and do not need to be tested even if they are exposed to someone with a known Covid-19 infection unless they are experiencing COVID-19 symptoms.

Physical distancing is no longer necessary for the fully vaccinated either.

The CDC is still encouraging people to wash their hands regularly to reduce the spread of all infections, not just Covid-19.

Camps are encouraged to routinely clean high-touch surfaces and shared objects. Good ventilation helps to stop the spread of the disease. Camps should open windows when possible, use air filters and turn on fans. Activities should happen outdoors as much as possible, the agency says.

If a camp does have an outbreak, the CDC would like the camp to contact the state or local public health department and work with those experts to isolate people with symptoms and to make sure that those who have symptoms can get tested. The camp should also quarantine any unvaccinated close contacts of anyone who has symptoms.

Camps with unvaccinated campers or staff should use multiple prevention strategies to protect those who aren’t vaccinated. The CDC said in those cases, physical distancing will be one of the important tools to help stop the spread of Covid-19.

Grouping children together, creating small groups of campers that stay together throughout the day can help minimize exposure, regardless of whether they are vaccinated or not. Masks will help protect the unvaccinated, and strongly encouraged indoors for those who are not fully vaccinated.

In general, people don’t need to wear masks for outdoor activities, unless people are in prolonged contact in an area with high transmission of the coronavirus, the CDC still recommends masking for people who are not fully vaccinated. Currently, nearly 7% of the US population lives in a community with a high level of Covid-19 transmission.

As far as what constitutes prolonged contact, CDC Director Dr. Rochelle Walensky told CNN’s Chief Medical Correspondent Dr. Sanjay Gupta Friday, that is a bit like asking, “Is your shirt too long or too short?” Team sports are probably OK, she said; a mosh pit, probably not.

Masks should never be worn during water sports, since a wet mask could make it difficult to breath and wet masks don’t work as well. Campers shouldn’t sleep in them either.

For people who aren’t fully vaccinated, routine screening can help find cases, particularly asymptomatic cases, and prevent the spread of the disease.

For kids in day camps, parents should watch to see if their children have any symptoms of Covid-19 and if they do they should keep those kids home when they are sick. Overnight camps should do daily health checks for symptoms.

Weekly screening for staff that isn’t fully vaccinated could also help reduce transmission of the virus. Camps should also create flexible and supportive sick leave policies to encourage staff to stay home or out of activities if they are sick.

The CDC strongly encourages camps to communicate clearly and openly with staff about any changes to procedures and activities and to train staff to recognize any signs of emotional stress or trauma.

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Camps should encourage staff to take a break from Covid-19 stories and social media if they feel overwhelmed and to encourage staff and campers to talk with people that they trust about their concerns and how they are feeling.

“Youth camps can play an important role in the lives of children, including supporting their social, emotional, and physical development,” the guidelines said. “This interim guidance is intended to help camp administrators operate camps while slowing the spread of the virus that causes COVID-19 thereby protecting campers, their families, staff, and communities.”

Ben Tinker, Michael Nedelman and CNN’s Chief Medical Correspondent Dr. Sanjay Gupta contributed to this report.