(CNN) Each summer, as Lauren Rutkowski and her husband Joel await the arrival of energized, sun-kissed children for their seven-week camp, the couple surveys the canoes and paddleboards, the arts and crafts, the food menus -- and every camper's vaccination records.
Measles outbreaks in the United States continue to grow, rising to 1,044 cases nationwide so far this year. In response, more camp owners and the camping industry are urging families to follow vaccination policies.
Some camps that require all participants to be vaccinated against measles, even if parents have religious objections, have not accepted campers who are not immunized.
These efforts to prevent the measles virus from traveling to and within camps aren't in vain. Medical experts warn that the virus can quickly spread in close quarters.
"It's fair to say that a lot of camps that perhaps were accepting things like religious and philosophical exemptions have made the decision not to accept those," said Lauren Rutkowski, the owner and director of Camp IHC in Pennsylvania, which is accredited under the American Camp Association and does not accept nonmedical exemptions.
As for the camp, "we always review medical records as they come in, and we really have been double-checking more of the international staff members' medical forms because different countries have different ways of submitting them," she said.
What has changed, Rutkowski said, is that Camp IHC often participates in inter-camp sports activities with more than 30 other camps within Wayne County, Pennsylvania, and this year the Wayne County Camping Alliance has required all participants in inter-camp sports to disclose whether they received their measles, mumps and rubella vaccine.
The US Centers for Disease Control and Prevention recommends children get two doses of the MMR vaccine: the first at 12 to 15 months and the second at 4 to 6 years old.
"That was a significant change that was made in Wayne County that I think really helps protect the families who are choosing to send their children to our camps over the course of the summer," Rutkowski said.
"I was really interested in finding out the Camp Alliance's position on immunizations, because it's one thing for me to ensure my community are immunized but if other camps that are coming onto my property or I'm going to theirs are not enforcing immunizations, that obviously puts my community at risk," she said.
She added that the growing attention on preventing measles from spreading to camps reminded her of when swine flu was a concern among camp owners in 2009. That year, the H1N1 strain of swine flu infected many people -- approximately 60.8 million cases, 274,304 hospitalizations and 12,469 deaths occurred in the United States, according to the CDC.
"Similar to measles, it can be left behind on door handles, elevator buttons, that kind of thing," Rutkowski said.
"Although camps have been dealing with an increase in adenovirus and things like that, we are ready and equipped to deal with those things with the protocols that we already have in place," she said. "With things like swine flu and then now with the measles outbreak, it's stepped it up a notch and has caused camps to really look at their protocols and then maybe make some amendments -- like for example whether or not you're going to accept exemptions to immunization."
A camp's decision to accept religious or philosophical exemptions typically falls in line with what its state or city requires for schools.
New York is the epicenter of the US outbreak; more than 800 people there have become sick, and New Yorkers have infected people in four other states. Last week, New York Gov. Andrew Cuomo signed legislation requiring schoolchildren to be vaccinated statewide, even if parents have religious objections. In other words, the legislation removes nonmedical exemptions from school vaccination requirements.
"So with that, especially this summer, camps have definitely taken the stand where many that previously may have accepted religious exemptions are saying, 'No not this summer. We're sorry,' " said Susie Lupert, executive director of the American Camp Association's New York and New Jersey region.
"Camps are accepting the fact that they might be losing families over that, and some families have come back to camp and said, 'You know what, we're willing to come back this summer and get the MMR,' because they really want their child to attend camp," she said.
A study published last year in the Journal of Pharmacy Practice previously found that the MMR vaccine was among the vaccinations required or recommended for campers by at least 80% of camps in New York.
Camps that are regulated and accredited with the association do their due diligence to track medical records and make sure campers are not at a heightened risk of infectious diseases.
Yet "there are thousands and thousands of camps across this country that are unregulated -- they're not licensed; they're not keeping track of medical records; they're not doing background checks on staff -- and there's lots of loopholes for how a camp can get away with this," Lupert said.
"Parents need to do their research and make sure they are choosing a camp that at the minimum is regulated and that in our opinion should be accredited with our association," she said.
On Monday, the American Academy of Pediatrics published new recommendations for health and safety practices at summer camps, recommending that before starting, all campers and staff should be up to date on their immunizations.
The recommendations describe nonmedical exemptions for required immunizations as "inappropriate" and note that "these exemptions should be eliminated by camps."
The recommendations are not to "exclude" or "isolate" children, "but it's really about keeping the children safe and protected," said Dr. CharlRe' Slaughter-Atiemo, a pediatrician at the University of Maryland Medical System in White Plains, who was not involved in the American Academy of Pediatrics statement.
She described the public health threat that the nation's measles outbreak could bring to summer camps as "scary" and "a little bit dangerous." She encouraged parents to vaccinate their children, especially if they plan to attend a camp this summer.
"For any public school, and honestly for any center-based camp or daycare, children are required to submit a vaccine record when they are applying for these programs -- and whether a program accepts them or not is obviously at their discretion," Slaughter-Atiemo said, referencing how some may accept philosophical or religious exemptions while others may not.
"New York, Texas, Florida, California -- all of those areas where you have a lot of people traveling internationally and going back and forth; those are the big high-risk areas," she said. "So for sure in those areas, I'm sure there are a lot of camps and programs that are making it mandatory for kids to get the vaccine before being enrolled in the camp."
For now. the rules and policies relating to vaccination requirements at camps can still vary by state, county and even individual camp programs.
When it comes to schools, for example, "there's no federal laws but there are some different laws by state. Some states allow only medical exemptions. Some allow medical exemptions and then also different religious or philosophical exemptions," said Brittany Kmush, an assistant professor at Syracuse University in New York, who specializes in infectious diseases.
She added that the measles virus can easily spread in an enclosed environment such as a sleepover summer camp.
If an infected person coughs or sneezes, the measles virus can linger infectious in the air for up to two hours, even after that infected person leaves the area.
"So it's very contagious -- a very contagious disease -- and if one child comes to a camp with the measles virus and can spread it, then it puts the other children at risk," Kmush said.
"You're not going to send them to summer camp without sunscreen," she added. "You should probably send them with all their vaccinations too, because you want to let them have the best time that they can at camp, and if they're sick they're not going to be able to."