A new strain of flu that likely came from Asia has sickened thousands of dogs in the Midwest, experts say.

The new dog flu virus, which has not been seen before in U.S. dogs, has infected more than 1,000 dogs and is responsible for six dog deaths in Illinois, Wisconsin, Ohio and Indiana, according to experts from the University of Wisconsin-Madison and Cornell University who have been collecting and testing samples of the virus.

"The dog population here has never seen this strain before," said Dr. Keith Poulsen, a professor of veterinary medicine at the University of Wisconsin-Madison. [10 Deadly Diseases That Hopped Across Species]

The canine sickness causes symptoms similar to those of the human flu, such as coughing, nasal discharge, fever and loss of appetite, though a small percentage of dogs can be carriers of the virus without showing symptoms, Poulsen said.

The virus is likely spread through nose-to-nose contact with other dogs, which occurs at doggy day care centers, veterinary clinics and dog parks, he added.

The virus doesn't appear to infect humans, Poulsen said. Although the possibility of a dog-human transfer of the virus can't be ruled out, "I think it's a very low risk," he said. "There have been reports of cats getting sick from direct contact with dogs, although there hasn't been a virus-positive cat reported yet," he said.

Poulsen recommended commonsense measures to prevent more dogs in the region from getting or spreading the virus. "If you go to dog parks, keep your dog on a leash, and avoid densely populated dog areas, especially if you have a very young dog or a very old dog whose immune system is compromised," he said. Also, "if your dog is sick, don't take him anywhere," he added.

The virus has an incubation period of about one to three days, and the infected animal can be contagious for up to 14 days, Poulsen said. The symptoms usually last about five to seven days, though the cough can persist for several weeks, he added.

The new virus is different from the previous strain of dog flu, H3N8, that's been circulating in the United States since 2004. The new strain, known as H3N2, has been found in animals in China and Korea, and an infected animal probably brought it to Chicago, Poulsen said.

There is a vaccine for the previous U.S. dog flu strain, but it's generally given only to dogs at high risk of getting infected, and experts don't know if the vaccine protects against the new strain. A few pharmaceutical companies have started working on a new vaccine, but it will probably be four to six months before it becomes available, Poulsen said.

Copyright 2015 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.