A rabies epidemic in wild animals is continuing to spread through Northern Virginia, with 86 cases reported this year in Fairfax, Loudoun and Fauquier counties, according to state health officials.

That is more than three-fourths of the 112 cases reported statewide so far this year.

The two most recent cases in Fairfax were found within the last two weeks near the Fair Oaks Mall, located in western Fairfax County near the intersection of Routes 50 and 66.

The epidemic began last spring on the western fringes of Virginia and spread eastward, with the heaviest concentration of cases in areas of Loudoun and Fauquier counties. Loudoun health officials have reported 54 cases this year; Fauquier officials have recorded 20.

Five rabid raccoons have been found in Fairfax County this year, the first reported cases there in three years. Four of the rabid raccoons were found in outlying neighborhoods in the western part of the county, but the fifth case was discovered about a quarter of a mile from densely populated Arlington County. That discovery of a rabid animal so near the more urban jurisdictions of Arlington and Alexandria alarmed health officials in both areas, neither of which has had a case of rabies reported yet this year.

All but 12 of the 112 rabid animals discovered this year were raccoons, health officials said. Rabies also has been found this year in nine skunks, one dog, one cat and one fox.

In 1981, 166 rabies cases were reported in Virginia--almost five times the 35 cases discovered in 1980.

In neighboring Maryland, the largest rabies outbreak in 27 years has infected the wild animal population in western counties. There, reports of rabies jumped 25 percent last year to 50 confirmed cases, up from 37 cases recorded in 1980. So far this year, 14 cases of rabies have been reported: 12 raccoons, one cow and a bat.

The rabid bat was found in Montgomery County. Prince George's County has recorded no rabies cases this year.

Health officials in both states blame hunting clubs for starting the worst rabies outbreak in years. They accuse the clubs of importing infected raccoons into Virginia from North Carolina, which has seen dramatic increases in reports of rabies for the past few years.

The entire nation is experiencing its worst rabies epidemic since 1954, according to Kenneth Bernard of the National Center for Disease Control in Atlanta. Health officials said they don't know what has caused the nationwide outbreak.

As a precaution, health officials have begun encouraging cat owners to have their pets vaccinated against rabies.

"Vaccinations have cut down rabies cases in dogs greatly in the last 30 years," said one health official. "Dogs were the primary carriers of rabies during the '40s and '50s until state laws required rabies vaccinations for dogs."