It's just like the Legionnaire's disease panic in Philadelphia a while back, Hank Drake explained today. "For a while no one would go within five miles of Philadelphia. But that's all forgotten."

And so it will be with the Three Mile Island nuclear scare, Drake hopes, because it will be partly his responsibility to make sure that a 300-room Marriott hotel-just eight miles north of the Three Mile Island nuclear generating plant-will stay full. Marriott has started construction and will hold a formal groundbreaking ceremony at the hotel site on Wednesday.

Nearly two months after the nation's first major nuclear accident, local business people and state officials are hoping the public will forget what lit them up on the nation's map. At the same time, they want to keep business from the biggest new tourist attraction in the state, the Three Mile Island reactors.

Even Marriott is billing the hotel's groundbreaking as "the first major financial investment in the Harrisburg region" since the Three Mile Island accident.

With a mixture of hype and hope, local business people are saying the economy here is recovering after near death in the middle of March and much of April, the height of the scare. No official analysis has been made of the accident on local business.

Marriott officials had cooled toward the idea of a hotel so near such a hot spot, according to Drake, director of marketing for the hotel. But the $1 billion hotel decided to go ahead with the groundbreaking because otherwise, the site is ideal.

The public's "memories are short," Drake said as he sat in the lobby of Marriott's competitor, directly across the road, the Host Inn. "They'll forget about it."

But even though there is preoccupation with an even more recent crisis, the gasoline shortage, the public has not quite forgotten Three Mile Island. For this area, that's not all bad.

Shopkeepers in Middletown, seven miles away, still feel the crush of tourists. About 50 to 100 out-of-town visitors a week who come to see the reactors stop by Dave Martin's clothing store, which is gearing up for another order of "hell no, I don't glow" T-shirts that sell for $4.50, according to salesman Dick Bates.

Color 10-by-14-inch photos of the nuclear plant are still in demand, at the town newsstand. During a 15-minute stretch in front of the plant's four cylindrical generators today, a busload of senior citizens are tourists from New Jersey, Delaware and Georgia stopped on the road shoulder to take a look.

Enchoing the fearlessness of the tourists, a visitor from Newark, Del., with his wife and pet poodle, told a reporter, "You wouldn't be here if it wasn't safe. President Carter wouldn't have come here if it wasn't stafe."

Tourists visiting the Pennysylvania Dutch country south of Middletown "swing up here and take in Three Mile Island." Bates said. Marriott hopes to get a little of that tourist business, Drake said.

Most people here admit that business was dead for the first couple of weeks after the incident began.

"Three Mile Island is past," said Host Inn manager Edward Davis. "Some (customers) joke about it and ask about it. Something's always happening. It's just another episode."

During April, "we lost money . . . That week we lost a mint. We lost food and beverage business in April. For May, we're ahead," Davis said. During April, Davis had to close his restaurant for two days because the waitresses left after hearing a false radio report about an explosion at the nuclear plant, Davis said. But the hotel's daily events calendar was full with at least five conventions today, and a dozen tourists were basking around the outdoor pool.

For a while, businesses outside of Pennsylvania were refusing the state's goods-not just milk, but even Pennsylvania-made shoes and tractors, according to Steven Fink, a spokesman for the State Department of Commerce. "Some companies wouldn't deliver products to Pennsylvania," Fink said. "Those outside the area panicked more than those inside the area. The fact that (Marriott) has broken ground here is encouraging."

The state's second-largest industry, tourism, has rebounded, Fink said. During the crisis, "travel was hard hit. Millions of dollars of convention business, bookings and meetings were canceled," Fink said.

A spokesman for the Hershey amusement park, about 10 miles from Harrisburg, said attendance so far has been down but the might the attributed the rainy weather. Group bookings are up compared with the same time last year, the spokesman said. "We're no longer concerned with (Three Mile Island's) effect," the spokesman for the 72-acre park said.

Marriott is expected to complete its 10-story hotel by the summer of 1980, Drake said. Amenities include a 200-seat restaurant, a 200-seat cocktail lounge, a grand ballroom seating up to 1,000 for conventions and seven additional meeting rooms. CAPTION: Picture, Tourists photographing the Three mile Island nuclear power plant: The Public's "memories are short." AP