A deadly disease that causes internal hemorrhaging is sweeping through the deer population in California, including several Bay Area counties where people have spotted drooling animals suffering from seizures and gripped by vomiting and diarrhea, wildlife veterinarians said Thursday.

The outbreak, called adenovirus hemorrhagic disease, has been confirmed in Napa, Santa Clara, Sonoma, Tehama and Yolo counties, but it may well have moved into other areas, said Brandon Munk, senior wildlife veterinarian for the California Department of Fish and Wildlife.

“Providing attractants for deer — food, salt licks or even water — is against the law for good reason,” said Munk, who works in the department’s Wildlife Investigations Laboratory, in Rancho Cordova (Sacramento County).

Munk said the contagion can infect deer, elk and other cervids, but black-tailed deer appear to be most susceptible.

He said people can also help wildlife veterinarians track and study the disease by reporting sightings of sick or dead deer.