NEW YORK — All dogs coming into the U.S. from other countries must be at least 6 months old and microchipped to help prevent the spread of rabies, according to new government rules published on May 8.

The new rules require vaccination for dogs that have been in countries where rabies is common. The update applies to dogs brought in by breeders or rescue groups as well as pets traveling with their U.S. owners.

“This new regulation is going to address the current challenges that we’re facing,” said Emily Pieracci, a rabies expert at the Centers for Disease Control and Prevention who was involved in drafting the updated regulations.

The CDC posted the new rules in the federal register on Wednesday. They take effect Aug. 1 when a temporary 2021 order expires. That order suspended bringing in dogs from more than 100 countries where rabies is still a problem.

The new rules require all dogs entering the U.S. to be at least 6 months, old enough to be vaccinated if required and for the shots to take effect; have a microchip placed under their skin with a code that can be used to verify rabies vaccination; and have completed a new CDC import form.

There may be additional restrictions and requirements based on where the dog was the previous six months, which may include blood testing from CDC-approved labs.

The CDC regulations were last updated in 1956, and a lot has changed, Pieracci said. More people travel internationally with their pets, and more rescue groups and breeders have set up overseas operations to meet the demand for pets, she said. Now, about 1 million dogs enter the U.S. each year.

Dogs were once common carriers of the rabies virus in the U.S. but the type that normally circulates in dogs was eliminated through vaccinations in the 1970s. The virus invades the central nervous system and is usually a fatal disease in animals and humans. It’s most commonly spread through a bite from an infected animal. There is no cure for it once symptoms begin.

Four rabid dogs have been identified entering the U.S. since 2015, and officials worried more might get through. CDC officials also were seeing an increase of incomplete or fraudulent rabies vaccination certificates and more puppies denied entry because they weren't old enough to be fully vaccinated.

A draft version of the updated regulations last year drew a range of public comments.

Deborah Williams lives in Western New York, and regularly crosses the border to Canada and back with her 12-year-old dog Sam.

“Sam lives in the United States. He was born in the United States. He was vaccinated in the United States," said Williams. "If we go over to Canada for the afternoon, when we come back, he's not being imported. He's just returning to his home.”

She has concerns about the changes.

“I don't think the CDC and also the lawmakers in Washington have any concept of what border life is like,” she said. 

Sam is vaccinated, has a microchip and is regularly checked out by a vet, but would not be good to cross come Aug. 1. Williams she’s not sure if her microchip meets requirements and Sam's two vets are not USDA-accredited. That's a common issue, especially in rural areas.

“There are people who are affected by this for whom there is not such a veterinarian for hundreds of miles,” Williams said.

The new regulations only apply to dogs coming into the U.S.

The CDC confirmed there is no exception for service animals and dogs who don’t meet the requirements could be denied entry, meaning some might still need to check all the boxes and then some, but now in a foreign country.

“This ruling from the CDC only creates more burdens than not,” said U.S. Rep. Tim Kennedy.

He sent a letter to the CDC emphasizing the need for flexibility, saying:

"In our region, many families regularly travel between the United States and Canada, often accompanied by their beloved pets. Whether they are dual citizens, have family in Canada, or own second homes there, these stricter requirements will affect local families who wish to bring their dogs across the US-Canada land border. The six-month age requirement for dogs to enter the United States, and the need for additional documentation and certification, such as the proposed CDC Dog Import Form and USDA endorsed Certification of U.S.-Issued Rabies Vaccination, will create barriers for families who simply wish to bring their dogs to family homes or second residences.

I understand the importance of ensuring the health and safety of both human and animal populations, especially in light of public health concerns such as rabies. However, I believe there is a need for flexibility in these regulations, particularly for border communities which utilize frequent land crossings where the risk of disease transmission is minimal. I respectfully request that the CDC consider providing an exception to these regulations for dogs traveling via land crossings in border communities between low-risk countries. This would alleviate the burden on families who rely on the ability to travel with their pets and would still maintain the integrity of public health measures."

“I don't think now is the time to start burdening families with dogs at the border, especially when we're seeing backups that ought to be streamlined to begin with,” Kennedy added. “We want to make it easier for people to go back and forth across the border, especially families with dogs.”

Aug. 1 also comes days before the Canadian Civic Holiday long weekend, potentially creating more chaos at the border.

“It's going to be a super nightmare if they keep the Aug. 1 date,” Williams.

The Associated Press contributed to this report.